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Merge git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus 

* git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux-2.6-for-linus:
  lguest and virtio: cleanup struct definitions to Linux style.
  lguest: update commentry
  lguest: fix comment style
  virtio: refactor find_vqs
  virtio: delete vq from list
  virtio: fix memory leak on device removal
  lguest: fix descriptor corruption in example launcher
  lguest: dereferencing freed mem in add_eventfd()
This commit is contained in:
Linus Torvalds 2009-07-30 16:45:03 -07:00
parent ec30c5f3a1 1842f23c05
commit 6ae7d6f019
22 changed files with 2429 additions and 1239 deletions
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721
Documentation/lguest/lguest.c
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File diff suppressed because it is too large Load Diff

3
arch/x86/include/asm/lguest.h
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@ -17,8 +17,7 @@
/* Pages for switcher itself, then two pages per cpu */
#define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * nr_cpu_ids)
/* We map at -4M (-2M when PAE is activated) for ease of mapping
* into the guest (one PTE page). */
/* We map at -4M (-2M for PAE) for ease of mapping (one PTE page). */
#ifdef CONFIG_X86_PAE
#define SWITCHER_ADDR 0xFFE00000
#else

18
arch/x86/include/asm/lguest_hcall.h
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@ -30,27 +30,27 @@
#include <asm/hw_irq.h>
#include <asm/kvm_para.h>
/*G:030 But first, how does our Guest contact the Host to ask for privileged
/*G:030
* But first, how does our Guest contact the Host to ask for privileged
* operations? There are two ways: the direct way is to make a "hypercall",
* to make requests of the Host Itself.
*
* We use the KVM hypercall mechanism. Seventeen hypercalls are
* available: the hypercall number is put in the %eax register, and the
* arguments (when required) are placed in %ebx, %ecx, %edx and %esi.
* If a return value makes sense, it's returned in %eax.
* We use the KVM hypercall mechanism, though completely different hypercall
* numbers. Seventeen hypercalls are available: the hypercall number is put in
* the %eax register, and the arguments (when required) are placed in %ebx,
* %ecx, %edx and %esi. If a return value makes sense, it's returned in %eax.
*
* Grossly invalid calls result in Sudden Death at the hands of the vengeful
* Host, rather than returning failure. This reflects Winston Churchill's
* definition of a gentleman: "someone who is only rude intentionally". */
/*:*/
* definition of a gentleman: "someone who is only rude intentionally".
:*/
/* Can't use our min() macro here: needs to be a constant */
#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)
#define LHCALL_RING_SIZE 64
struct hcall_args {
/* These map directly onto eax, ebx, ecx, edx and esi
* in struct lguest_regs */
/* These map directly onto eax/ebx/ecx/edx/esi in struct lguest_regs */
unsigned long arg0, arg1, arg2, arg3, arg4;
};

509
arch/x86/lguest/boot.c
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File diff suppressed because it is too large Load Diff

112
arch/x86/lguest/i386_head.S
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@ -5,7 +5,8 @@
#include <asm/thread_info.h>
#include <asm/processor-flags.h>
/*G:020 Our story starts with the kernel booting into startup_32 in
/*G:020
* Our story starts with the kernel booting into startup_32 in
* arch/x86/kernel/head_32.S. It expects a boot header, which is created by
* the bootloader (the Launcher in our case).
*
@ -21,11 +22,14 @@
* data without remembering to subtract __PAGE_OFFSET!
*
* The .section line puts this code in .init.text so it will be discarded after
* boot. */
* boot.
*/
.section .init.text, "ax", @progbits
ENTRY(lguest_entry)
/* We make the "initialization" hypercall now to tell the Host about
* us, and also find out where it put our page tables. */
/*
* We make the "initialization" hypercall now to tell the Host about
* us, and also find out where it put our page tables.
*/
movl $LHCALL_LGUEST_INIT, %eax
movl $lguest_data - __PAGE_OFFSET, %ebx
.byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */
@ -33,13 +37,14 @@ ENTRY(lguest_entry)
/* Set up the initial stack so we can run C code. */
movl $(init_thread_union+THREAD_SIZE),%esp
/* Jumps are relative, and we're running __PAGE_OFFSET too low at the
* moment. */
/* Jumps are relative: we're running __PAGE_OFFSET too low. */
jmp lguest_init+__PAGE_OFFSET
/*G:055 We create a macro which puts the assembler code between lgstart_ and
* lgend_ markers. These templates are put in the .text section: they can't be
* discarded after boot as we may need to patch modules, too. */
/*G:055
* We create a macro which puts the assembler code between lgstart_ and lgend_
* markers. These templates are put in the .text section: they can't be
* discarded after boot as we may need to patch modules, too.
*/
.text
#define LGUEST_PATCH(name, insns...) \
lgstart_##name: insns; lgend_##name:; \
@ -48,83 +53,103 @@ ENTRY(lguest_entry)
LGUEST_PATCH(cli, movl $0, lguest_data+LGUEST_DATA_irq_enabled)
LGUEST_PATCH(pushf, movl lguest_data+LGUEST_DATA_irq_enabled, %eax)
/*G:033 But using those wrappers is inefficient (we'll see why that doesn't
* matter for save_fl and irq_disable later). If we write our routines
* carefully in assembler, we can avoid clobbering any registers and avoid
* jumping through the wrapper functions.
/*G:033
* But using those wrappers is inefficient (we'll see why that doesn't matter
* for save_fl and irq_disable later). If we write our routines carefully in
* assembler, we can avoid clobbering any registers and avoid jumping through
* the wrapper functions.
*
* I skipped over our first piece of assembler, but this one is worth studying
* in a bit more detail so I'll describe in easy stages. First, the routine
* to enable interrupts: */
* in a bit more detail so I'll describe in easy stages. First, the routine to
* enable interrupts:
*/
ENTRY(lg_irq_enable)
/* The reverse of irq_disable, this sets lguest_data.irq_enabled to
* X86_EFLAGS_IF (ie. "Interrupts enabled"). */
/*
* The reverse of irq_disable, this sets lguest_data.irq_enabled to
* X86_EFLAGS_IF (ie. "Interrupts enabled").
*/
movl $X86_EFLAGS_IF, lguest_data+LGUEST_DATA_irq_enabled
/* But now we need to check if the Host wants to know: there might have
/*
* But now we need to check if the Host wants to know: there might have
* been interrupts waiting to be delivered, in which case it will have
* set lguest_data.irq_pending to X86_EFLAGS_IF. If it's not zero, we
* jump to send_interrupts, otherwise we're done. */
* jump to send_interrupts, otherwise we're done.
*/
testl $0, lguest_data+LGUEST_DATA_irq_pending
jnz send_interrupts
/* One cool thing about x86 is that you can do many things without using
/*
* One cool thing about x86 is that you can do many things without using
* a register. In this case, the normal path hasn't needed to save or
* restore any registers at all! */
* restore any registers at all!
*/
ret
send_interrupts:
/* OK, now we need a register: eax is used for the hypercall number,
/*
* OK, now we need a register: eax is used for the hypercall number,
* which is LHCALL_SEND_INTERRUPTS.
*
* We used not to bother with this pending detection at all, which was
* much simpler. Sooner or later the Host would realize it had to
* send us an interrupt. But that turns out to make performance 7
* times worse on a simple tcp benchmark. So now we do this the hard
* way. */
* way.
*/
pushl %eax
movl $LHCALL_SEND_INTERRUPTS, %eax
/* This is a vmcall instruction (same thing that KVM uses). Older
/*
* This is a vmcall instruction (same thing that KVM uses). Older
* assembler versions might not know the "vmcall" instruction, so we
* create one manually here. */
* create one manually here.
*/
.byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */
/* Put eax back the way we found it. */
popl %eax
ret
/* Finally, the "popf" or "restore flags" routine. The %eax register holds the
/*
* Finally, the "popf" or "restore flags" routine. The %eax register holds the
* flags (in practice, either X86_EFLAGS_IF or 0): if it's X86_EFLAGS_IF we're
* enabling interrupts again, if it's 0 we're leaving them off. */
* enabling interrupts again, if it's 0 we're leaving them off.
*/
ENTRY(lg_restore_fl)
/* This is just "lguest_data.irq_enabled = flags;" */
movl %eax, lguest_data+LGUEST_DATA_irq_enabled
/* Now, if the %eax value has enabled interrupts and
/*
* Now, if the %eax value has enabled interrupts and
* lguest_data.irq_pending is set, we want to tell the Host so it can
* deliver any outstanding interrupts. Fortunately, both values will
* be X86_EFLAGS_IF (ie. 512) in that case, and the "testl"
* instruction will AND them together for us. If both are set, we
* jump to send_interrupts. */
* jump to send_interrupts.
*/
testl lguest_data+LGUEST_DATA_irq_pending, %eax
jnz send_interrupts
/* Again, the normal path has used no extra registers. Clever, huh? */
ret
/*:*/
/* These demark the EIP range where host should never deliver interrupts. */
.global lguest_noirq_start
.global lguest_noirq_end
/*M:004 When the Host reflects a trap or injects an interrupt into the Guest,
* it sets the eflags interrupt bit on the stack based on
* lguest_data.irq_enabled, so the Guest iret logic does the right thing when
* restoring it. However, when the Host sets the Guest up for direct traps,
* such as system calls, the processor is the one to push eflags onto the
* stack, and the interrupt bit will be 1 (in reality, interrupts are always
* enabled in the Guest).
/*M:004
* When the Host reflects a trap or injects an interrupt into the Guest, it
* sets the eflags interrupt bit on the stack based on lguest_data.irq_enabled,
* so the Guest iret logic does the right thing when restoring it. However,
* when the Host sets the Guest up for direct traps, such as system calls, the
* processor is the one to push eflags onto the stack, and the interrupt bit
* will be 1 (in reality, interrupts are always enabled in the Guest).
*
* This turns out to be harmless: the only trap which should happen under Linux
* with interrupts disabled is Page Fault (due to our lazy mapping of vmalloc
* regions), which has to be reflected through the Host anyway. If another
* trap *does* go off when interrupts are disabled, the Guest will panic, and
* we'll never get to this iret! :*/
* we'll never get to this iret!
:*/
/*G:045 There is one final paravirt_op that the Guest implements, and glancing
* at it you can see why I left it to last. It's *cool*! It's in *assembler*!
/*G:045
* There is one final paravirt_op that the Guest implements, and glancing at it
* you can see why I left it to last. It's *cool*! It's in *assembler*!
*
* The "iret" instruction is used to return from an interrupt or trap. The
* stack looks like this:
@ -148,15 +173,18 @@ ENTRY(lg_restore_fl)
* return to userspace or wherever. Our solution to this is to surround the
* code with lguest_noirq_start: and lguest_noirq_end: labels. We tell the
* Host that it is *never* to interrupt us there, even if interrupts seem to be
* enabled. */
* enabled.
*/
ENTRY(lguest_iret)
pushl %eax
movl 12(%esp), %eax
lguest_noirq_start:
/* Note the %ss: segment prefix here. Normal data accesses use the
/*
* Note the %ss: segment prefix here. Normal data accesses use the
* "ds" segment, but that will have already been restored for whatever
* we're returning to (such as userspace): we can't trust it. The %ss:
* prefix makes sure we use the stack segment, which is still valid. */
* prefix makes sure we use the stack segment, which is still valid.
*/
movl %eax,%ss:lguest_data+LGUEST_DATA_irq_enabled
popl %eax
iret

119
drivers/lguest/core.c
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@ -1,6 +1,8 @@
/*P:400 This contains run_guest() which actually calls into the Host<->Guest
/*P:400
* This contains run_guest() which actually calls into the Host<->Guest
* Switcher and analyzes the return, such as determining if the Guest wants the
* Host to do something. This file also contains useful helper routines. :*/
* Host to do something. This file also contains useful helper routines.
:*/
#include <linux/module.h>
#include <linux/stringify.h>
#include <linux/stddef.h>
@ -24,7 +26,8 @@ static struct page **switcher_page;
/* This One Big lock protects all inter-guest data structures. */
DEFINE_MUTEX(lguest_lock);
/*H:010 We need to set up the Switcher at a high virtual address. Remember the
/*H:010
* We need to set up the Switcher at a high virtual address. Remember the
* Switcher is a few hundred bytes of assembler code which actually changes the
* CPU to run the Guest, and then changes back to the Host when a trap or
* interrupt happens.
@ -33,7 +36,8 @@ DEFINE_MUTEX(lguest_lock);
* Host since it will be running as the switchover occurs.
*
* Trying to map memory at a particular address is an unusual thing to do, so
* it's not a simple one-liner. */
* it's not a simple one-liner.
*/
static __init int map_switcher(void)
{
int i, err;
@ -47,8 +51,10 @@ static __init int map_switcher(void)
* easy.
*/
/* We allocate an array of struct page pointers. map_vm_area() wants
* this, rather than just an array of pages. */
/*
* We allocate an array of struct page pointers. map_vm_area() wants
* this, rather than just an array of pages.
*/
switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
GFP_KERNEL);
if (!switcher_page) {
@ -56,8 +62,10 @@ static __init int map_switcher(void)
goto out;
}
/* Now we actually allocate the pages. The Guest will see these pages,
* so we make sure they're zeroed. */
/*
* Now we actually allocate the pages. The Guest will see these pages,
* so we make sure they're zeroed.
*/
for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
unsigned long addr = get_zeroed_page(GFP_KERNEL);
if (!addr) {
@ -67,19 +75,23 @@ static __init int map_switcher(void)
switcher_page[i] = virt_to_page(addr);
}
/* First we check that the Switcher won't overlap the fixmap area at
/*
* First we check that the Switcher won't overlap the fixmap area at
* the top of memory. It's currently nowhere near, but it could have
* very strange effects if it ever happened. */
* very strange effects if it ever happened.
*/
if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
err = -ENOMEM;
printk("lguest: mapping switcher would thwack fixmap\n");
goto free_pages;
}
/* Now we reserve the "virtual memory area" we want: 0xFFC00000
/*
* Now we reserve the "virtual memory area" we want: 0xFFC00000
* (SWITCHER_ADDR). We might not get it in theory, but in practice
* it's worked so far. The end address needs +1 because __get_vm_area
* allocates an extra guard page, so we need space for that. */
* allocates an extra guard page, so we need space for that.
*/
switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR
+ (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
@ -89,11 +101,13 @@ static __init int map_switcher(void)
goto free_pages;
}
/* This code actually sets up the pages we've allocated to appear at
/*
* This code actually sets up the pages we've allocated to appear at
* SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the
* kind of pages we're mapping (kernel pages), and a pointer to our
* array of struct pages. It increments that pointer, but we don't
* care. */
* care.
*/
pagep = switcher_page;
err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep);
if (err) {
@ -101,8 +115,10 @@ static __init int map_switcher(void)
goto free_vma;
}
/* Now the Switcher is mapped at the right address, we can't fail!
* Copy in the compiled-in Switcher code (from <arch>_switcher.S). */
/*
* Now the Switcher is mapped at the right address, we can't fail!
* Copy in the compiled-in Switcher code (from <arch>_switcher.S).
*/
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);
@ -124,8 +140,7 @@ out:
}
/*:*/
/* Cleaning up the mapping when the module is unloaded is almost...
* too easy. */
/* Cleaning up the mapping when the module is unloaded is almost... too easy. */
static void unmap_switcher(void)
{
unsigned int i;
@ -151,16 +166,19 @@ static void unmap_switcher(void)
* But we can't trust the Guest: it might be trying to access the Launcher
* code. We have to check that the range is below the pfn_limit the Launcher
* gave us. We have to make sure that addr + len doesn't give us a false
* positive by overflowing, too. */
* positive by overflowing, too.
*/
bool lguest_address_ok(const struct lguest *lg,
unsigned long addr, unsigned long len)
{
return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
}
/* This routine copies memory from the Guest. Here we can see how useful the
/*
* This routine copies memory from the Guest. Here we can see how useful the
* kill_lguest() routine we met in the Launcher can be: we return a random
* value (all zeroes) instead of needing to return an error. */
* value (all zeroes) instead of needing to return an error.
*/
void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes)
{
if (!lguest_address_ok(cpu->lg, addr, bytes)
@ -181,9 +199,11 @@ void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b,
}
/*:*/
/*H:030 Let's jump straight to the the main loop which runs the Guest.
/*H:030
* Let's jump straight to the the main loop which runs the Guest.
* Remember, this is called by the Launcher reading /dev/lguest, and we keep
* going around and around until something interesting happens. */
* going around and around until something interesting happens.
*/
int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
{
/* We stop running once the Guest is dead. */
@ -195,10 +215,17 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
if (cpu->hcall)
do_hypercalls(cpu);
/* It's possible the Guest did a NOTIFY hypercall to the
* Launcher, in which case we return from the read() now. */
/*
* It's possible the Guest did a NOTIFY hypercall to the
* Launcher.
*/
if (cpu->pending_notify) {
/*
* Does it just needs to write to a registered
* eventfd (ie. the appropriate virtqueue thread)?
*/
if (!send_notify_to_eventfd(cpu)) {
/* OK, we tell the main Laucher. */
if (put_user(cpu->pending_notify, user))
return -EFAULT;
return sizeof(cpu->pending_notify);
@ -209,29 +236,39 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
if (signal_pending(current))
return -ERESTARTSYS;
/* Check if there are any interrupts which can be delivered now:
/*
* Check if there are any interrupts which can be delivered now:
* if so, this sets up the hander to be executed when we next
* run the Guest. */
* run the Guest.
*/
irq = interrupt_pending(cpu, &more);
if (irq < LGUEST_IRQS)
try_deliver_interrupt(cpu, irq, more);
/* All long-lived kernel loops need to check with this horrible
/*
* All long-lived kernel loops need to check with this horrible
* thing called the freezer. If the Host is trying to suspend,
* it stops us. */
* it stops us.
*/
try_to_freeze();
/* Just make absolutely sure the Guest is still alive. One of
* those hypercalls could have been fatal, for example. */
/*
* Just make absolutely sure the Guest is still alive. One of
* those hypercalls could have been fatal, for example.
*/
if (cpu->lg->dead)
break;
/* If the Guest asked to be stopped, we sleep. The Guest's
* clock timer will wake us. */
/*
* If the Guest asked to be stopped, we sleep. The Guest's
* clock timer will wake us.
*/
if (cpu->halted) {
set_current_state(TASK_INTERRUPTIBLE);
/* Just before we sleep, make sure no interrupt snuck in
* which we should be doing. */
/*
* Just before we sleep, make sure no interrupt snuck in
* which we should be doing.
*/
if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
set_current_state(TASK_RUNNING);
else
@ -239,8 +276,10 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
continue;
}
/* OK, now we're ready to jump into the Guest. First we put up
* the "Do Not Disturb" sign: */
/*
* OK, now we're ready to jump into the Guest. First we put up
* the "Do Not Disturb" sign:
*/
local_irq_disable();
/* Actually run the Guest until something happens. */
@ -327,8 +366,10 @@ static void __exit fini(void)
}
/*:*/
/* The Host side of lguest can be a module. This is a nice way for people to
* play with it. */
/*
* The Host side of lguest can be a module. This is a nice way for people to
* play with it.
*/
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");

145
drivers/lguest/hypercalls.c
View File

@ -1,8 +1,10 @@
/*P:500 Just as userspace programs request kernel operations through a system
/*P:500
* Just as userspace programs request kernel operations through a system
* call, the Guest requests Host operations through a "hypercall". You might
* notice this nomenclature doesn't really follow any logic, but the name has
* been around for long enough that we're stuck with it. As you'd expect, this
* code is basically a one big switch statement. :*/
* code is basically a one big switch statement.
:*/
/* Copyright (C) 2006 Rusty Russell IBM Corporation
@ -28,30 +30,41 @@
#include <asm/pgtable.h>
#include "lg.h"
/*H:120 This is the core hypercall routine: where the Guest gets what it wants.
* Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */
/*H:120
* This is the core hypercall routine: where the Guest gets what it wants.
* Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
*/
static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
{
switch (args->arg0) {
case LHCALL_FLUSH_ASYNC:
/* This call does nothing, except by breaking out of the Guest
* it makes us process all the asynchronous hypercalls. */
/*
* This call does nothing, except by breaking out of the Guest
* it makes us process all the asynchronous hypercalls.
*/
break;
case LHCALL_SEND_INTERRUPTS:
/* This call does nothing too, but by breaking out of the Guest
* it makes us process any pending interrupts. */
/*
* This call does nothing too, but by breaking out of the Guest
* it makes us process any pending interrupts.
*/
break;
case LHCALL_LGUEST_INIT:
/* You can't get here unless you're already initialized. Don't
* do that. */
/*
* You can't get here unless you're already initialized. Don't
* do that.
*/
kill_guest(cpu, "already have lguest_data");
break;
case LHCALL_SHUTDOWN: {
/* Shutdown is such a trivial hypercall that we do it in four
* lines right here. */
char msg[128];
/* If the lgread fails, it will call kill_guest() itself; the
* kill_guest() with the message will be ignored. */
/*
* Shutdown is such a trivial hypercall that we do it in five
* lines right here.
*
* If the lgread fails, it will call kill_guest() itself; the
* kill_guest() with the message will be ignored.
*/
__lgread(cpu, msg, args->arg1, sizeof(msg));
msg[sizeof(msg)-1] = '\0';
kill_guest(cpu, "CRASH: %s", msg);
@ -60,16 +73,17 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
break;
}
case LHCALL_FLUSH_TLB:
/* FLUSH_TLB comes in two flavors, depending on the
* argument: */
/* FLUSH_TLB comes in two flavors, depending on the argument: */
if (args->arg1)
guest_pagetable_clear_all(cpu);
else
guest_pagetable_flush_user(cpu);
break;
/* All these calls simply pass the arguments through to the right
* routines. */
/*
* All these calls simply pass the arguments through to the right
* routines.
*/
case LHCALL_NEW_PGTABLE:
guest_new_pagetable(cpu, args->arg1);
break;
@ -112,15 +126,16 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
}
}
/*:*/
/*H:124 Asynchronous hypercalls are easy: we just look in the array in the
/*H:124
* Asynchronous hypercalls are easy: we just look in the array in the
* Guest's "struct lguest_data" to see if any new ones are marked "ready".
*
* We are careful to do these in order: obviously we respect the order the
* Guest put them in the ring, but we also promise the Guest that they will
* happen before any normal hypercall (which is why we check this before
* checking for a normal hcall). */
* checking for a normal hcall).
*/
static void do_async_hcalls(struct lg_cpu *cpu)
{
unsigned int i;
@ -133,22 +148,28 @@ static void do_async_hcalls(struct lg_cpu *cpu)
/* We process "struct lguest_data"s hcalls[] ring once. */
for (i = 0; i < ARRAY_SIZE(st); i++) {
struct hcall_args args;
/* We remember where we were up to from last time. This makes
/*
* We remember where we were up to from last time. This makes
* sure that the hypercalls are done in the order the Guest
* places them in the ring. */
* places them in the ring.
*/
unsigned int n = cpu->next_hcall;
/* 0xFF means there's no call here (yet). */
if (st[n] == 0xFF)
break;
/* OK, we have hypercall. Increment the "next_hcall" cursor,
* and wrap back to 0 if we reach the end. */
/*
* OK, we have hypercall. Increment the "next_hcall" cursor,
* and wrap back to 0 if we reach the end.
*/
if (++cpu->next_hcall == LHCALL_RING_SIZE)
cpu->next_hcall = 0;
/* Copy the hypercall arguments into a local copy of
* the hcall_args struct. */
/*
* Copy the hypercall arguments into a local copy of the
* hcall_args struct.
*/
if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
sizeof(struct hcall_args))) {
kill_guest(cpu, "Fetching async hypercalls");
@ -164,19 +185,25 @@ static void do_async_hcalls(struct lg_cpu *cpu)
break;
}
/* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first. */
/*
* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first.
*/
if (cpu->pending_notify)
break;
}
}
/* Last of all, we look at what happens first of all. The very first time the
* Guest makes a hypercall, we end up here to set things up: */
/*
* Last of all, we look at what happens first of all. The very first time the
* Guest makes a hypercall, we end up here to set things up:
*/
static void initialize(struct lg_cpu *cpu)
{
/* You can't do anything until you're initialized. The Guest knows the
* rules, so we're unforgiving here. */
/*
* You can't do anything until you're initialized. The Guest knows the
* rules, so we're unforgiving here.
*/
if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
return;
@ -185,32 +212,44 @@ static void initialize(struct lg_cpu *cpu)
if (lguest_arch_init_hypercalls(cpu))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
/* The Guest tells us where we're not to deliver interrupts by putting
* the range of addresses into "struct lguest_data". */
/*
* The Guest tells us where we're not to deliver interrupts by putting
* the range of addresses into "struct lguest_data".
*/
if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
|| get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
/* We write the current time into the Guest's data page once so it can
* set its clock. */
/*
* We write the current time into the Guest's data page once so it can
* set its clock.
*/
write_timestamp(cpu);
/* page_tables.c will also do some setup. */
page_table_guest_data_init(cpu);
/* This is the one case where the above accesses might have been the
/*
* This is the one case where the above accesses might have been the
* first write to a Guest page. This may have caused a copy-on-write
* fault, but the old page might be (read-only) in the Guest
* pagetable. */
* pagetable.
*/
guest_pagetable_clear_all(cpu);
}
/*:*/
/*M:013 If a Guest reads from a page (so creates a mapping) that it has never
/*M:013
* If a Guest reads from a page (so creates a mapping) that it has never
* written to, and then the Launcher writes to it (ie. the output of a virtual
* device), the Guest will still see the old page. In practice, this never
* happens: why would the Guest read a page which it has never written to? But
* a similar scenario might one day bite us, so it's worth mentioning. :*/
* a similar scenario might one day bite us, so it's worth mentioning.
*
* Note that if we used a shared anonymous mapping in the Launcher instead of
* mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
* need that to switch the Launcher to processes (away from threads) anyway.
:*/
/*H:100
* Hypercalls
@ -229,17 +268,22 @@ void do_hypercalls(struct lg_cpu *cpu)
return;
}
/* The Guest has initialized.
/*
* The Guest has initialized.
*
* Look in the hypercall ring for the async hypercalls: */
* Look in the hypercall ring for the async hypercalls:
*/
do_async_hcalls(cpu);
/* If we stopped reading the hypercall ring because the Guest did a
/*
* If we stopped reading the hypercall ring because the Guest did a
* NOTIFY to the Launcher, we want to return now. Otherwise we do
* the hypercall. */
* the hypercall.
*/
if (!cpu->pending_notify) {
do_hcall(cpu, cpu->hcall);
/* Tricky point: we reset the hcall pointer to mark the
/*
* Tricky point: we reset the hcall pointer to mark the
* hypercall as "done". We use the hcall pointer rather than
* the trap number to indicate a hypercall is pending.
* Normally it doesn't matter: the Guest will run again and
@ -248,13 +292,16 @@ void do_hypercalls(struct lg_cpu *cpu)
* However, if we are signalled or the Guest sends I/O to the
* Launcher, the run_guest() loop will exit without running the
* Guest. When it comes back it would try to re-run the
* hypercall. Finding that bug sucked. */
* hypercall. Finding that bug sucked.
*/
cpu->hcall = NULL;
}
}
/* This routine supplies the Guest with time: it's used for wallclock time at
* initial boot and as a rough time source if the TSC isn't available. */
/*
* This routine supplies the Guest with time: it's used for wallclock time at
* initial boot and as a rough time source if the TSC isn't available.
*/
void write_timestamp(struct lg_cpu *cpu)
{
struct timespec now;

288
drivers/lguest/interrupts_and_traps.c
View File

@ -1,4 +1,5 @@
/*P:800 Interrupts (traps) are complicated enough to earn their own file.
/*P:800
* Interrupts (traps) are complicated enough to earn their own file.
* There are three classes of interrupts:
*
* 1) Real hardware interrupts which occur while we're running the Guest,
@ -10,7 +11,8 @@
* just like real hardware would deliver them. Traps from the Guest can be set
* up to go directly back into the Guest, but sometimes the Host wants to see
* them first, so we also have a way of "reflecting" them into the Guest as if
* they had been delivered to it directly. :*/
* they had been delivered to it directly.
:*/
#include <linux/uaccess.h>
#include <linux/interrupt.h>
#include <linux/module.h>
@ -26,8 +28,10 @@ static unsigned long idt_address(u32 lo, u32 hi)
return (lo & 0x0000FFFF) | (hi & 0xFFFF0000);
}
/* The "type" of the interrupt handler is a 4 bit field: we only support a
* couple of types. */
/*
* The "type" of the interrupt handler is a 4 bit field: we only support a
* couple of types.
*/
static int idt_type(u32 lo, u32 hi)
{
return (hi >> 8) & 0xF;
@ -39,8 +43,10 @@ static bool idt_present(u32 lo, u32 hi)
return (hi & 0x8000);
}
/* We need a helper to "push" a value onto the Guest's stack, since that's a
* big part of what delivering an interrupt does. */
/*
* We need a helper to "push" a value onto the Guest's stack, since that's a
* big part of what delivering an interrupt does.
*/
static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
{
/* Stack grows upwards: move stack then write value. */
@ -48,7 +54,8 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
lgwrite(cpu, *gstack, u32, val);
}
/*H:210 The set_guest_interrupt() routine actually delivers the interrupt or
/*H:210
* The set_guest_interrupt() routine actually delivers the interrupt or
* trap. The mechanics of delivering traps and interrupts to the Guest are the
* same, except some traps have an "error code" which gets pushed onto the
* stack as well: the caller tells us if this is one.
@ -59,7 +66,8 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
*
* We set up the stack just like the CPU does for a real interrupt, so it's
* identical for the Guest (and the standard "iret" instruction will undo
* it). */
* it).
*/
static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
bool has_err)
{
@ -67,20 +75,26 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
u32 eflags, ss, irq_enable;
unsigned long virtstack;
/* There are two cases for interrupts: one where the Guest is already
/*
* There are two cases for interrupts: one where the Guest is already
* in the kernel, and a more complex one where the Guest is in
* userspace. We check the privilege level to find out. */
* userspace. We check the privilege level to find out.
*/
if ((cpu->regs->ss&0x3) != GUEST_PL) {
/* The Guest told us their kernel stack with the SET_STACK
* hypercall: both the virtual address and the segment */
/*
* The Guest told us their kernel stack with the SET_STACK
* hypercall: both the virtual address and the segment.
*/
virtstack = cpu->esp1;
ss = cpu->ss1;
origstack = gstack = guest_pa(cpu, virtstack);
/* We push the old stack segment and pointer onto the new
/*
* We push the old stack segment and pointer onto the new
* stack: when the Guest does an "iret" back from the interrupt
* handler the CPU will notice they're dropping privilege
* levels and expect these here. */
* levels and expect these here.
*/
push_guest_stack(cpu, &gstack, cpu->regs->ss);
push_guest_stack(cpu, &gstack, cpu->regs->esp);
} else {
@ -91,18 +105,22 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
origstack = gstack = guest_pa(cpu, virtstack);
}
/* Remember that we never let the Guest actually disable interrupts, so
/*
* Remember that we never let the Guest actually disable interrupts, so
* the "Interrupt Flag" bit is always set. We copy that bit from the
* Guest's "irq_enabled" field into the eflags word: we saw the Guest
* copy it back in "lguest_iret". */
* copy it back in "lguest_iret".
*/
eflags = cpu->regs->eflags;
if (get_user(irq_enable, &cpu->lg->lguest_data->irq_enabled) == 0
&& !(irq_enable & X86_EFLAGS_IF))
eflags &= ~X86_EFLAGS_IF;
/* An interrupt is expected to push three things on the stack: the old
/*
* An interrupt is expected to push three things on the stack: the old
* "eflags" word, the old code segment, and the old instruction
* pointer. */
* pointer.
*/
push_guest_stack(cpu, &gstack, eflags);
push_guest_stack(cpu, &gstack, cpu->regs->cs);
push_guest_stack(cpu, &gstack, cpu->regs->eip);
@ -111,15 +129,19 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
if (has_err)
push_guest_stack(cpu, &gstack, cpu->regs->errcode);
/* Now we've pushed all the old state, we change the stack, the code
* segment and the address to execute. */
/*
* Now we've pushed all the old state, we change the stack, the code
* segment and the address to execute.
*/
cpu->regs->ss = ss;
cpu->regs->esp = virtstack + (gstack - origstack);
cpu->regs->cs = (__KERNEL_CS|GUEST_PL);
cpu->regs->eip = idt_address(lo, hi);
/* There are two kinds of interrupt handlers: 0xE is an "interrupt
* gate" which expects interrupts to be disabled on entry. */
/*
* There are two kinds of interrupt handlers: 0xE is an "interrupt
* gate" which expects interrupts to be disabled on entry.
*/
if (idt_type(lo, hi) == 0xE)
if (put_user(0, &cpu->lg->lguest_data->irq_enabled))
kill_guest(cpu, "Disabling interrupts");
@ -130,7 +152,8 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
*
* interrupt_pending() returns the first pending interrupt which isn't blocked
* by the Guest. It is called before every entry to the Guest, and just before
* we go to sleep when the Guest has halted itself. */
* we go to sleep when the Guest has halted itself.
*/
unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more)
{
unsigned int irq;
@ -140,8 +163,10 @@ unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more)
if (!cpu->lg->lguest_data)
return LGUEST_IRQS;
/* Take our "irqs_pending" array and remove any interrupts the Guest
* wants blocked: the result ends up in "blk". */
/*
* Take our "irqs_pending" array and remove any interrupts the Guest
* wants blocked: the result ends up in "blk".
*/
if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts,
sizeof(blk)))
return LGUEST_IRQS;
@ -154,16 +179,20 @@ unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more)
return irq;
}
/* This actually diverts the Guest to running an interrupt handler, once an
* interrupt has been identified by interrupt_pending(). */
/*
* This actually diverts the Guest to running an interrupt handler, once an
* interrupt has been identified by interrupt_pending().
*/
void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
{
struct desc_struct *idt;
BUG_ON(irq >= LGUEST_IRQS);
/* They may be in the middle of an iret, where they asked us never to
* deliver interrupts. */
/*
* They may be in the middle of an iret, where they asked us never to
* deliver interrupts.
*/
if (cpu->regs->eip >= cpu->lg->noirq_start &&
(cpu->regs->eip < cpu->lg->noirq_end))
return;
@ -187,29 +216,37 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
}
}
/* Look at the IDT entry the Guest gave us for this interrupt. The
/*
* Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
* over them. */
* over them.
*/
idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
/* set_guest_interrupt() takes the interrupt descriptor and a
/*
* set_guest_interrupt() takes the interrupt descriptor and a
* flag to say whether this interrupt pushes an error code onto
* the stack as well: virtual interrupts never do. */
* the stack as well: virtual interrupts never do.
*/
set_guest_interrupt(cpu, idt->a, idt->b, false);
}
/* Every time we deliver an interrupt, we update the timestamp in the
/*
* Every time we deliver an interrupt, we update the timestamp in the
* Guest's lguest_data struct. It would be better for the Guest if we
* did this more often, but it can actually be quite slow: doing it
* here is a compromise which means at least it gets updated every
* timer interrupt. */
* timer interrupt.
*/
write_timestamp(cpu);
/* If there are no other interrupts we want to deliver, clear
* the pending flag. */
/*
* If there are no other interrupts we want to deliver, clear
* the pending flag.
*/
if (!more)
put_user(0, &cpu->lg->lguest_data->irq_pending);
}
@ -217,24 +254,29 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
/* And this is the routine when we want to set an interrupt for the Guest. */
void set_interrupt(struct lg_cpu *cpu, unsigned int irq)
{
/* Next time the Guest runs, the core code will see if it can deliver
* this interrupt. */
/*
* Next time the Guest runs, the core code will see if it can deliver
* this interrupt.
*/
set_bit(irq, cpu->irqs_pending);
/* Make sure it sees it; it might be asleep (eg. halted), or
* running the Guest right now, in which case kick_process()
* will knock it out. */
/*
* Make sure it sees it; it might be asleep (eg. halted), or running
* the Guest right now, in which case kick_process() will knock it out.
*/
if (!wake_up_process(cpu->tsk))
kick_process(cpu->tsk);
}
/*:*/
/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent
/*
* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent
* me a patch, so we support that too. It'd be a big step for lguest if half
* the Plan 9 user base were to start using it.
*
* Actually now I think of it, it's possible that Ron *is* half the Plan 9
* userbase. Oh well. */
* userbase. Oh well.
*/
static bool could_be_syscall(unsigned int num)
{
/* Normal Linux SYSCALL_VECTOR or reserved vector? */
@ -274,9 +316,11 @@ void free_interrupts(void)
clear_bit(syscall_vector, used_vectors);
}
/*H:220 Now we've got the routines to deliver interrupts, delivering traps like
/*H:220
* Now we've got the routines to deliver interrupts, delivering traps like
* page fault is easy. The only trick is that Intel decided that some traps
* should have error codes: */
* should have error codes:
*/
static bool has_err(unsigned int trap)
{
return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);
@ -285,13 +329,17 @@ static bool has_err(unsigned int trap)
/* deliver_trap() returns true if it could deliver the trap. */
bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
{
/* Trap numbers are always 8 bit, but we set an impossible trap number
* for traps inside the Switcher, so check that here. */
/*
* Trap numbers are always 8 bit, but we set an impossible trap number
* for traps inside the Switcher, so check that here.
*/
if (num >= ARRAY_SIZE(cpu->arch.idt))
return false;
/* Early on the Guest hasn't set the IDT entries (or maybe it put a
* bogus one in): if we fail here, the Guest will be killed. */
/*
* Early on the Guest hasn't set the IDT entries (or maybe it put a
* bogus one in): if we fail here, the Guest will be killed.
*/
if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b))
return false;
set_guest_interrupt(cpu, cpu->arch.idt[num].a,
@ -299,7 +347,8 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
return true;
}
/*H:250 Here's the hard part: returning to the Host every time a trap happens
/*H:250
* Here's the hard part: returning to the Host every time a trap happens
* and then calling deliver_trap() and re-entering the Guest is slow.
* Particularly because Guest userspace system calls are traps (usually trap
* 128).
@ -311,69 +360,87 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
* the other hypervisors would beat it up at lunchtime.
*
* This routine indicates if a particular trap number could be delivered
* directly. */
* directly.
*/
static bool direct_trap(unsigned int num)
{
/* Hardware interrupts don't go to the Guest at all (except system
* call). */
/*
* Hardware interrupts don't go to the Guest at all (except system
* call).
*/
if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num))
return false;
/* The Host needs to see page faults (for shadow paging and to save the
/*
* The Host needs to see page faults (for shadow paging and to save the
* fault address), general protection faults (in/out emulation) and
* device not available (TS handling), invalid opcode fault (kvm hcall),
* and of course, the hypercall trap. */
* and of course, the hypercall trap.
*/
return num != 14 && num != 13 && num != 7 &&
num != 6 && num != LGUEST_TRAP_ENTRY;
}
/*:*/
/*M:005 The Guest has the ability to turn its interrupt gates into trap gates,
/*M:005
* The Guest has the ability to turn its interrupt gates into trap gates,
* if it is careful. The Host will let trap gates can go directly to the
* Guest, but the Guest needs the interrupts atomically disabled for an
* interrupt gate. It can do this by pointing the trap gate at instructions
* within noirq_start and noirq_end, where it can safely disable interrupts. */
* within noirq_start and noirq_end, where it can safely disable interrupts.
*/
/*M:006 The Guests do not use the sysenter (fast system call) instruction,
/*M:006
* The Guests do not use the sysenter (fast system call) instruction,
* because it's hardcoded to enter privilege level 0 and so can't go direct.
* It's about twice as fast as the older "int 0x80" system call, so it might
* still be worthwhile to handle it in the Switcher and lcall down to the
* Guest. The sysenter semantics are hairy tho: search for that keyword in
* entry.S :*/
* entry.S
:*/
/*H:260 When we make traps go directly into the Guest, we need to make sure
/*H:260
* When we make traps go directly into the Guest, we need to make sure
* the kernel stack is valid (ie. mapped in the page tables). Otherwise, the
* CPU trying to deliver the trap will fault while trying to push the interrupt
* words on the stack: this is called a double fault, and it forces us to kill
* the Guest.
*
* Which is deeply unfair, because (literally!) it wasn't the Guests' fault. */
* Which is deeply unfair, because (literally!) it wasn't the Guests' fault.
*/
void pin_stack_pages(struct lg_cpu *cpu)
{
unsigned int i;
/* Depending on the CONFIG_4KSTACKS option, the Guest can have one or
* two pages of stack space. */
/*
* Depending on the CONFIG_4KSTACKS option, the Guest can have one or
* two pages of stack space.
*/
for (i = 0; i < cpu->lg->stack_pages; i++)
/* The stack grows *upwards*, so the address we're given is the
/*
* The stack grows *upwards*, so the address we're given is the
* start of the page after the kernel stack. Subtract one to
* get back onto the first stack page, and keep subtracting to
* get to the rest of the stack pages. */
* get to the rest of the stack pages.
*/
pin_page(cpu, cpu->esp1 - 1 - i * PAGE_SIZE);
}
/* Direct traps also mean that we need to know whenever the Guest wants to use
/*
* Direct traps also mean that we need to know whenever the Guest wants to use
* a different kernel stack, so we can change the IDT entries to use that
* stack. The IDT entries expect a virtual address, so unlike most addresses
* the Guest gives us, the "esp" (stack pointer) value here is virtual, not
* physical.
*
* In Linux each process has its own kernel stack, so this happens a lot: we
* change stacks on each context switch. */
* change stacks on each context switch.
*/
void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages)
{
/* You are not allowed have a stack segment with privilege level 0: bad
* Guest! */
/*
* You're not allowed a stack segment with privilege level 0: bad Guest!
*/
if ((seg & 0x3) != GUEST_PL)
kill_guest(cpu, "bad stack segment %i", seg);
/* We only expect one or two stack pages. */
@ -387,11 +454,15 @@ void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages)
pin_stack_pages(cpu);
}
/* All this reference to mapping stacks leads us neatly into the other complex
* part of the Host: page table handling. */
/*
* All this reference to mapping stacks leads us neatly into the other complex
* part of the Host: page table handling.
*/
/*H:235 This is the routine which actually checks the Guest's IDT entry and
* transfers it into the entry in "struct lguest": */
/*H:235
* This is the routine which actually checks the Guest's IDT entry and
* transfers it into the entry in "struct lguest":
*/
static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap,
unsigned int num, u32 lo, u32 hi)
{
@ -407,30 +478,38 @@ static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap,
if (type != 0xE && type != 0xF)
kill_guest(cpu, "bad IDT type %i", type);
/* We only copy the handler address, present bit, privilege level and
/*
* We only copy the handler address, present bit, privilege level and
* type. The privilege level controls where the trap can be triggered
* manually with an "int" instruction. This is usually GUEST_PL,
* except for system calls which userspace can use. */
* except for system calls which userspace can use.
*/
trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);
trap->b = (hi&0xFFFFEF00);
}
/*H:230 While we're here, dealing with delivering traps and interrupts to the
/*H:230
* While we're here, dealing with delivering traps and interrupts to the
* Guest, we might as well complete the picture: how the Guest tells us where
* it wants them to go. This would be simple, except making traps fast
* requires some tricks.
*
* We saw the Guest setting Interrupt Descriptor Table (IDT) entries with the
* LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here. */
* LHCALL_LOAD_IDT_ENTRY hypercall before: that comes here.
*/
void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi)
{
/* Guest never handles: NMI, doublefault, spurious interrupt or
* hypercall. We ignore when it tries to set them. */
/*
* Guest never handles: NMI, doublefault, spurious interrupt or
* hypercall. We ignore when it tries to set them.
*/
if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY)
return;
/* Mark the IDT as changed: next time the Guest runs we'll know we have
* to copy this again. */
/*
* Mark the IDT as changed: next time the Guest runs we'll know we have
* to copy this again.
*/
cpu->changed |= CHANGED_IDT;
/* Check that the Guest doesn't try to step outside the bounds. */
@ -440,9 +519,11 @@ void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int num, u32 lo, u32 hi)
set_trap(cpu, &cpu->arch.idt[num], num, lo, hi);
}
/* The default entry for each interrupt points into the Switcher routines which
/*
* The default entry for each interrupt points into the Switcher routines which
* simply return to the Host. The run_guest() loop will then call
* deliver_trap() to bounce it back into the Guest. */
* deliver_trap() to bounce it back into the Guest.
*/
static void default_idt_entry(struct desc_struct *idt,
int trap,
const unsigned long handler,
@ -451,13 +532,17 @@ static void default_idt_entry(struct desc_struct *idt,
/* A present interrupt gate. */
u32 flags = 0x8e00;
/* Set the privilege level on the entry for the hypercall: this allows
* the Guest to use the "int" instruction to trigger it. */
/*
* Set the privilege level on the entry for the hypercall: this allows
* the Guest to use the "int" instruction to trigger it.
*/
if (trap == LGUEST_TRAP_ENTRY)
flags |= (GUEST_PL << 13);
else if (base)
/* Copy priv. level from what Guest asked for. This allows
* debug (int 3) traps from Guest userspace, for example. */
/*
* Copy privilege level from what Guest asked for. This allows
* debug (int 3) traps from Guest userspace, for example.
*/
flags |= (base->b & 0x6000);
/* Now pack it into the IDT entry in its weird format. */
@ -475,16 +560,20 @@ void setup_default_idt_entries(struct lguest_ro_state *state,
default_idt_entry(&state->guest_idt[i], i, def[i], NULL);
}
/*H:240 We don't use the IDT entries in the "struct lguest" directly, instead
/*H:240
* We don't use the IDT entries in the "struct lguest" directly, instead
* we copy them into the IDT which we've set up for Guests on this CPU, just
* before we run the Guest. This routine does that copy. */
* before we run the Guest. This routine does that copy.
*/
void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt,
const unsigned long *def)
{
unsigned int i;
/* We can simply copy the direct traps, otherwise we use the default
* ones in the Switcher: they will return to the Host. */
/*
* We can simply copy the direct traps, otherwise we use the default
* ones in the Switcher: they will return to the Host.
*/
for (i = 0; i < ARRAY_SIZE(cpu->arch.idt); i++) {
const struct desc_struct *gidt = &cpu->arch.idt[i];
@ -492,14 +581,16 @@ void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt,
if (!direct_trap(i))
continue;
/* Only trap gates (type 15) can go direct to the Guest.
/*
* Only trap gates (type 15) can go direct to the Guest.
* Interrupt gates (type 14) disable interrupts as they are
* entered, which we never let the Guest do. Not present
* entries (type 0x0) also can't go direct, of course.
*
* If it can't go direct, we still need to copy the priv. level:
* they might want to give userspace access to a software
* interrupt. */
* interrupt.
*/
if (idt_type(gidt->a, gidt->b) == 0xF)
idt[i] = *gidt;
else
@ -518,7 +609,8 @@ void copy_traps(const struct lg_cpu *cpu, struct desc_struct *idt,
* the next timer interrupt (in nanoseconds). We use the high-resolution timer
* infrastructure to set a callback at that time.
*
* 0 means "turn off the clock". */
* 0 means "turn off the clock".
*/
void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta)
{
ktime_t expires;
@ -529,9 +621,11 @@ void guest_set_clockevent(struct lg_cpu *cpu, unsigned long delta)
return;
}
/* We use wallclock time here, so the Guest might not be running for
/*
* We use wallclock time here, so the Guest might not be running for
* all the time between now and the timer interrupt it asked for. This
* is almost always the right thing to do. */
* is almost always the right thing to do.
*/
expires = ktime_add_ns(ktime_get_real(), delta);
hrtimer_start(&cpu->hrt, expires, HRTIMER_MODE_ABS);
}

32
drivers/lguest/lg.h
View File

@ -16,15 +16,13 @@
void free_pagetables(void);
int init_pagetables(struct page **switcher_page, unsigned int pages);
struct pgdir
{
struct pgdir {
unsigned long gpgdir;
pgd_t *pgdir;
};
/* We have two pages shared with guests, per cpu. */
struct lguest_pages
{
struct lguest_pages {
/* This is the stack page mapped rw in guest */
char spare[PAGE_SIZE - sizeof(struct lguest_regs)];
struct lguest_regs regs;
@ -54,13 +52,13 @@ struct lg_cpu {
unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
/* At end of a page shared mapped over lguest_pages in guest. */
/* At end of a page shared mapped over lguest_pages in guest. */
unsigned long regs_page;
struct lguest_regs *regs;
struct lguest_pages *last_pages;
int cpu_pgd; /* which pgd this cpu is currently using */
int cpu_pgd; /* Which pgd this cpu is currently using */
/* If a hypercall was asked for, this points to the arguments. */
struct hcall_args *hcall;
@ -89,15 +87,17 @@ struct lg_eventfd_map {
};
/* The private info the thread maintains about the guest. */
struct lguest
{
struct lguest {
struct lguest_data __user *lguest_data;
struct lg_cpu cpus[NR_CPUS];
unsigned int nr_cpus;
u32 pfn_limit;
/* This provides the offset to the base of guest-physical
* memory in the Launcher. */
/*
* This provides the offset to the base of guest-physical memory in the
* Launcher.
*/
void __user *mem_base;
unsigned long kernel_address;
@ -122,11 +122,13 @@ bool lguest_address_ok(const struct lguest *lg,
void __lgread(struct lg_cpu *, void *, unsigned long, unsigned);
void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned);
/*H:035 Using memory-copy operations like that is usually inconvient, so we
/*H:035
* Using memory-copy operations like that is usually inconvient, so we
* have the following helper macros which read and write a specific type (often
* an unsigned long).
*
* This reads into a variable of the given type then returns that. */
* This reads into a variable of the given type then returns that.
*/
#define lgread(cpu, addr, type) \
({ type _v; __lgread((cpu), &_v, (addr), sizeof(_v)); _v; })
@ -140,9 +142,11 @@ void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned);
int run_guest(struct lg_cpu *cpu, unsigned long __user *user);
/* Helper macros to obtain the first 12 or the last 20 bits, this is only the
/*
* Helper macros to obtain the first 12 or the last 20 bits, this is only the
* first step in the migration to the kernel types. pte_pfn is already defined
* in the kernel. */
* in the kernel.
*/
#define pgd_flags(x) (pgd_val(x) & ~PAGE_MASK)
#define pgd_pfn(x) (pgd_val(x) >> PAGE_SHIFT)
#define pmd_flags(x) (pmd_val(x) & ~PAGE_MASK)

160
drivers/lguest/lguest_device.c
View File

@ -1,10 +1,12 @@
/*P:050 Lguest guests use a very simple method to describe devices. It's a
/*P:050
* Lguest guests use a very simple method to describe devices. It's a
* series of device descriptors contained just above the top of normal Guest
* memory.
*
* We use the standard "virtio" device infrastructure, which provides us with a
* console, a network and a block driver. Each one expects some configuration
* information and a "virtqueue" or two to send and receive data. :*/
* information and a "virtqueue" or two to send and receive data.
:*/
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/lguest_launcher.h>
@ -20,8 +22,10 @@
/* The pointer to our (page) of device descriptions. */
static void *lguest_devices;
/* For Guests, device memory can be used as normal memory, so we cast away the
* __iomem to quieten sparse. */
/*
* For Guests, device memory can be used as normal memory, so we cast away the
* __iomem to quieten sparse.
*/
static inline void *lguest_map(unsigned long phys_addr, unsigned long pages)
{
return (__force void *)ioremap_cache(phys_addr, PAGE_SIZE*pages);
@ -32,8 +36,10 @@ static inline void lguest_unmap(void *addr)
iounmap((__force void __iomem *)addr);
}
/*D:100 Each lguest device is just a virtio device plus a pointer to its entry
* in the lguest_devices page. */
/*D:100
* Each lguest device is just a virtio device plus a pointer to its entry
* in the lguest_devices page.
*/
struct lguest_device {
struct virtio_device vdev;
@ -41,9 +47,11 @@ struct lguest_device {
struct lguest_device_desc *desc;
};
/* Since the virtio infrastructure hands us a pointer to the virtio_device all
/*
* Since the virtio infrastructure hands us a pointer to the virtio_device all
* the time, it helps to have a curt macro to get a pointer to the struct
* lguest_device it's enclosed in. */
* lguest_device it's enclosed in.
*/
#define to_lgdev(vd) container_of(vd, struct lguest_device, vdev)
/*D:130
@ -55,7 +63,8 @@ struct lguest_device {
* the driver will look at them during setup.
*
* A convenient routine to return the device's virtqueue config array:
* immediately after the descriptor. */
* immediately after the descriptor.
*/
static struct lguest_vqconfig *lg_vq(const struct lguest_device_desc *desc)
{
return (void *)(desc + 1);
@ -98,10 +107,12 @@ static u32 lg_get_features(struct virtio_device *vdev)
return features;
}
/* The virtio core takes the features the Host offers, and copies the
* ones supported by the driver into the vdev->features array. Once
* that's all sorted out, this routine is called so we can tell the
* Host which features we understand and accept. */
/*
* The virtio core takes the features the Host offers, and copies the ones
* supported by the driver into the vdev->features array. Once that's all
* sorted out, this routine is called so we can tell the Host which features we
* understand and accept.
*/
static void lg_finalize_features(struct virtio_device *vdev)
{
unsigned int i, bits;
@ -112,10 +123,11 @@ static void lg_finalize_features(struct virtio_device *vdev)
/* Give virtio_ring a chance to accept features. */
vring_transport_features(vdev);
/* The vdev->feature array is a Linux bitmask: this isn't the
* same as a the simple array of bits used by lguest devices
* for features. So we do this slow, manual conversion which is
* completely general. */
/*
* The vdev->feature array is a Linux bitmask: this isn't the same as a
* the simple array of bits used by lguest devices for features. So we
* do this slow, manual conversion which is completely general.
*/
memset(out_features, 0, desc->feature_len);
bits = min_t(unsigned, desc->feature_len, sizeof(vdev->features)) * 8;
for (i = 0; i < bits; i++) {
@ -146,15 +158,19 @@ static void lg_set(struct virtio_device *vdev, unsigned int offset,
memcpy(lg_config(desc) + offset, buf, len);
}
/* The operations to get and set the status word just access the status field
* of the device descriptor. */
/*
* The operations to get and set the status word just access the status field
* of the device descriptor.
*/
static u8 lg_get_status(struct virtio_device *vdev)
{
return to_lgdev(vdev)->desc->status;
}
/* To notify on status updates, we (ab)use the NOTIFY hypercall, with the
* descriptor address of the device. A zero status means "reset". */
/*
* To notify on status updates, we (ab)use the NOTIFY hypercall, with the
* descriptor address of the device. A zero status means "reset".
*/
static void set_status(struct virtio_device *vdev, u8 status)
{
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
@ -191,8 +207,7 @@ static void lg_reset(struct virtio_device *vdev)
*/
/*D:140 This is the information we remember about each virtqueue. */
struct lguest_vq_info
{
struct lguest_vq_info {
/* A copy of the information contained in the device config. */
struct lguest_vqconfig config;
@ -200,13 +215,17 @@ struct lguest_vq_info
void *pages;
};
/* When the virtio_ring code wants to prod the Host, it calls us here and we
/*
* When the virtio_ring code wants to prod the Host, it calls us here and we
* make a hypercall. We hand the physical address of the virtqueue so the Host
* knows which virtqueue we're talking about. */
* knows which virtqueue we're talking about.
*/
static void lg_notify(struct virtqueue *vq)
{
/* We store our virtqueue information in the "priv" pointer of the
* virtqueue structure. */
/*
* We store our virtqueue information in the "priv" pointer of the
* virtqueue structure.
*/
struct lguest_vq_info *lvq = vq->priv;
kvm_hypercall1(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT);
@ -215,7 +234,8 @@ static void lg_notify(struct virtqueue *vq)
/* An extern declaration inside a C file is bad form. Don't do it. */
extern void lguest_setup_irq(unsigned int irq);
/* This routine finds the first virtqueue described in the configuration of
/*
* This routine finds the Nth virtqueue described in the configuration of
* this device and sets it up.
*
* This is kind of an ugly duckling. It'd be nicer to have a standard
@ -223,9 +243,7 @@ extern void lguest_setup_irq(unsigned int irq);
* everyone wants to do it differently. The KVM coders want the Guest to
* allocate its own pages and tell the Host where they are, but for lguest it's
* simpler for the Host to simply tell us where the pages are.
*
* So we provide drivers with a "find the Nth virtqueue and set it up"
* function. */
*/
static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
unsigned index,
void (*callback)(struct virtqueue *vq),
@ -244,9 +262,11 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
if (!lvq)
return ERR_PTR(-ENOMEM);
/* Make a copy of the "struct lguest_vqconfig" entry, which sits after
/*
* Make a copy of the "struct lguest_vqconfig" entry, which sits after
* the descriptor. We need a copy because the config space might not
* be aligned correctly. */
* be aligned correctly.
*/
memcpy(&lvq->config, lg_vq(ldev->desc)+index, sizeof(lvq->config));
printk("Mapping virtqueue %i addr %lx\n", index,
@ -261,8 +281,10 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
goto free_lvq;
}
/* OK, tell virtio_ring.c to set up a virtqueue now we know its size
* and we've got a pointer to its pages. */
/*
* OK, tell virtio_ring.c to set up a virtqueue now we know its size
* and we've got a pointer to its pages.
*/
vq = vring_new_virtqueue(lvq->config.num, LGUEST_VRING_ALIGN,
vdev, lvq->pages, lg_notify, callback, name);
if (!vq) {
@ -273,18 +295,23 @@ static struct virtqueue *lg_find_vq(struct virtio_device *vdev,
/* Make sure the interrupt is allocated. */
lguest_setup_irq(lvq->config.irq);
/* Tell the interrupt for this virtqueue to go to the virtio_ring
* interrupt handler. */
/* FIXME: We used to have a flag for the Host to tell us we could use
/*
* Tell the interrupt for this virtqueue to go to the virtio_ring
* interrupt handler.
*
* FIXME: We used to have a flag for the Host to tell us we could use
* the interrupt as a source of randomness: it'd be nice to have that
* back.. */
* back.
*/
err = request_irq(lvq->config.irq, vring_interrupt, IRQF_SHARED,
dev_name(&vdev->dev), vq);
if (err)
goto destroy_vring;
/* Last of all we hook up our 'struct lguest_vq_info" to the
* virtqueue's priv pointer. */
/*
* Last of all we hook up our 'struct lguest_vq_info" to the
* virtqueue's priv pointer.
*/
vq->priv = lvq;
return vq;
@ -358,11 +385,14 @@ static struct virtio_config_ops lguest_config_ops = {
.del_vqs = lg_del_vqs,
};
/* The root device for the lguest virtio devices. This makes them appear as
* /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2. */
/*
* The root device for the lguest virtio devices. This makes them appear as
* /sys/devices/lguest/0,1,2 not /sys/devices/0,1,2.
*/
static struct device *lguest_root;
/*D:120 This is the core of the lguest bus: actually adding a new device.
/*D:120
* This is the core of the lguest bus: actually adding a new device.
* It's a separate function because it's neater that way, and because an
* earlier version of the code supported hotplug and unplug. They were removed
* early on because they were never used.
@ -371,14 +401,14 @@ static struct device *lguest_root;
*
* It's worth reading this carefully: we start with a pointer to the new device
* descriptor in the "lguest_devices" page, and the offset into the device
* descriptor page so we can uniquely identify it if things go badly wrong. */
* descriptor page so we can uniquely identify it if things go badly wrong.
*/
static void add_lguest_device(struct lguest_device_desc *d,
unsigned int offset)
{
struct lguest_device *ldev;
/* Start with zeroed memory; Linux's device layer seems to count on
* it. */
/* Start with zeroed memory; Linux's device layer counts on it. */
ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
if (!ldev) {
printk(KERN_EMERG "Cannot allocate lguest dev %u type %u\n",
@ -388,17 +418,25 @@ static void add_lguest_device(struct lguest_device_desc *d,
/* This devices' parent is the lguest/ dir. */
ldev->vdev.dev.parent = lguest_root;
/* We have a unique device index thanks to the dev_index counter. */
/*
* The device type comes straight from the descriptor. There's also a
* device vendor field in the virtio_device struct, which we leave as
* 0.
*/
ldev->vdev.id.device = d->type;
/* We have a simple set of routines for querying the device's
* configuration information and setting its status. */
/*
* We have a simple set of routines for querying the device's
* configuration information and setting its status.
*/
ldev->vdev.config = &lguest_config_ops;
/* And we remember the device's descriptor for lguest_config_ops. */
ldev->desc = d;
/* register_virtio_device() sets up the generic fields for the struct
/*
* register_virtio_device() sets up the generic fields for the struct
* virtio_device and calls device_register(). This makes the bus
* infrastructure look for a matching driver. */
* infrastructure look for a matching driver.
*/
if (register_virtio_device(&ldev->vdev) != 0) {
printk(KERN_ERR "Failed to register lguest dev %u type %u\n",
offset, d->type);
@ -406,8 +444,10 @@ static void add_lguest_device(struct lguest_device_desc *d,
}
}
/*D:110 scan_devices() simply iterates through the device page. The type 0 is
* reserved to mean "end of devices". */
/*D:110
* scan_devices() simply iterates through the device page. The type 0 is
* reserved to mean "end of devices".
*/
static void scan_devices(void)
{
unsigned int i;
@ -426,7 +466,8 @@ static void scan_devices(void)
}
}
/*D:105 Fairly early in boot, lguest_devices_init() is called to set up the
/*D:105
* Fairly early in boot, lguest_devices_init() is called to set up the
* lguest device infrastructure. We check that we are a Guest by checking
* pv_info.name: there are other ways of checking, but this seems most
* obvious to me.
@ -437,7 +478,8 @@ static void scan_devices(void)
* correct sysfs incantation).
*
* Finally we call scan_devices() which adds all the devices found in the
* lguest_devices page. */
* lguest_devices page.
*/
static int __init lguest_devices_init(void)
{
if (strcmp(pv_info.name, "lguest") != 0)
@ -456,11 +498,13 @@ static int __init lguest_devices_init(void)
/* We do this after core stuff, but before the drivers. */
postcore_initcall(lguest_devices_init);
/*D:150 At this point in the journey we used to now wade through the lguest
/*D:150
* At this point in the journey we used to now wade through the lguest
* devices themselves: net, block and console. Since they're all now virtio
* devices rather than lguest-specific, I've decided to ignore them. Mostly,
* they're kind of boring. But this does mean you'll never experience the
* thrill of reading the forbidden love scene buried deep in the block driver.
*
* "make Launcher" beckons, where we answer questions like "Where do Guests
* come from?", and "What do you do when someone asks for optimization?". */
* come from?", and "What do you do when someone asks for optimization?".
*/

232
drivers/lguest/lguest_user.c
View File

@ -1,8 +1,9 @@
/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
* controls and communicates with the Guest. For example, the first write will
* tell us the Guest's memory layout, pagetable, entry point and kernel address
* offset. A read will run the Guest until something happens, such as a signal
* or the Guest doing a NOTIFY out to the Launcher. :*/
* tell us the Guest's memory layout and entry point. A read will run the
* Guest until something happens, such as a signal or the Guest doing a NOTIFY
* out to the Launcher.
:*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
@ -11,14 +12,41 @@
#include <linux/file.h>
#include "lg.h"
/*L:056
* Before we move on, let's jump ahead and look at what the kernel does when
* it needs to look up the eventfds. That will complete our picture of how we
* use RCU.
*
* The notification value is in cpu->pending_notify: we return true if it went
* to an eventfd.
*/
bool send_notify_to_eventfd(struct lg_cpu *cpu)
{
unsigned int i;
struct lg_eventfd_map *map;
/* lg->eventfds is RCU-protected */
/*
* This "rcu_read_lock()" helps track when someone is still looking at
* the (RCU-using) eventfds array. It's not actually a lock at all;
* indeed it's a noop in many configurations. (You didn't expect me to
* explain all the RCU secrets here, did you?)
*/
rcu_read_lock();
/*
* rcu_dereference is the counter-side of rcu_assign_pointer(); it
* makes sure we don't access the memory pointed to by
* cpu->lg->eventfds before cpu->lg->eventfds is set. Sounds crazy,
* but Alpha allows this! Paul McKenney points out that a really
* aggressive compiler could have the same effect:
* http://lists.ozlabs.org/pipermail/lguest/2009-July/001560.html
*
* So play safe, use rcu_dereference to get the rcu-protected pointer:
*/
map = rcu_dereference(cpu->lg->eventfds);
/*
* Simple array search: even if they add an eventfd while we do this,
* we'll continue to use the old array and just won't see the new one.
*/
for (i = 0; i < map->num; i++) {
if (map->map[i].addr == cpu->pending_notify) {
eventfd_signal(map->map[i].event, 1);
@ -26,19 +54,50 @@ bool send_notify_to_eventfd(struct lg_cpu *cpu)
break;
}
}
/* We're done with the rcu-protected variable cpu->lg->eventfds. */
rcu_read_unlock();
/* If we cleared the notification, it's because we found a match. */
return cpu->pending_notify == 0;
}
/*L:055
* One of the more tricksy tricks in the Linux Kernel is a technique called
* Read Copy Update. Since one point of lguest is to teach lguest journeyers
* about kernel coding, I use it here. (In case you're curious, other purposes
* include learning about virtualization and instilling a deep appreciation for
* simplicity and puppies).
*
* We keep a simple array which maps LHCALL_NOTIFY values to eventfds, but we
* add new eventfds without ever blocking readers from accessing the array.
* The current Launcher only does this during boot, so that never happens. But
* Read Copy Update is cool, and adding a lock risks damaging even more puppies
* than this code does.
*
* We allocate a brand new one-larger array, copy the old one and add our new
* element. Then we make the lg eventfd pointer point to the new array.
* That's the easy part: now we need to free the old one, but we need to make
* sure no slow CPU somewhere is still looking at it. That's what
* synchronize_rcu does for us: waits until every CPU has indicated that it has
* moved on to know it's no longer using the old one.
*
* If that's unclear, see http://en.wikipedia.org/wiki/Read-copy-update.
*/
static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
{
struct lg_eventfd_map *new, *old = lg->eventfds;
/*
* We don't allow notifications on value 0 anyway (pending_notify of
* 0 means "nothing pending").
*/
if (!addr)
return -EINVAL;
/* Replace the old array with the new one, carefully: others can
* be accessing it at the same time */
/*
* Replace the old array with the new one, carefully: others can
* be accessing it at the same time.
*/
new = kmalloc(sizeof(*new) + sizeof(new->map[0]) * (old->num + 1),
GFP_KERNEL);
if (!new)
@ -52,22 +111,41 @@ static int add_eventfd(struct lguest *lg, unsigned long addr, int fd)
new->map[new->num].addr = addr;
new->map[new->num].event = eventfd_ctx_fdget(fd);
if (IS_ERR(new->map[new->num].event)) {
int err = PTR_ERR(new->map[new->num].event);
kfree(new);
return PTR_ERR(new->map[new->num].event);
return err;
}
new->num++;
/* Now put new one in place. */
/*
* Now put new one in place: rcu_assign_pointer() is a fancy way of
* doing "lg->eventfds = new", but it uses memory barriers to make
* absolutely sure that the contents of "new" written above is nailed
* down before we actually do the assignment.
*
* We have to think about these kinds of things when we're operating on
* live data without locks.
*/
rcu_assign_pointer(lg->eventfds, new);
/* We're not in a big hurry. Wait until noone's looking at old
* version, then delete it. */
/*
* We're not in a big hurry. Wait until noone's looking at old
* version, then free it.
*/
synchronize_rcu();
kfree(old);
return 0;
}
/*L:052
* Receiving notifications from the Guest is usually done by attaching a
* particular LHCALL_NOTIFY value to an event filedescriptor. The eventfd will
* become readable when the Guest does an LHCALL_NOTIFY with that value.
*
* This is really convenient for processing each virtqueue in a separate
* thread.
*/
static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
{
unsigned long addr, fd;
@ -79,15 +157,22 @@ static int attach_eventfd(struct lguest *lg, const unsigned long __user *input)
if (get_user(fd, input) != 0)
return -EFAULT;
/*
* Just make sure two callers don't add eventfds at once. We really
* only need to lock against callers adding to the same Guest, so using
* the Big Lguest Lock is overkill. But this is setup, not a fast path.
*/
mutex_lock(&lguest_lock);
err = add_eventfd(lg, addr, fd);
mutex_unlock(&lguest_lock);
return 0;
return err;
}
/*L:050 Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
* number to /dev/lguest. */
/*L:050
* Sending an interrupt is done by writing LHREQ_IRQ and an interrupt
* number to /dev/lguest.
*/
static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
{
unsigned long irq;
@ -97,12 +182,18 @@ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
if (irq >= LGUEST_IRQS)
return -EINVAL;
/*
* Next time the Guest runs, the core code will see if it can deliver
* this interrupt.
*/
set_interrupt(cpu, irq);
return 0;
}
/*L:040 Once our Guest is initialized, the Launcher makes it run by reading
* from /dev/lguest. */
/*L:040
* Once our Guest is initialized, the Launcher makes it run by reading
* from /dev/lguest.
*/
static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
{
struct lguest *lg = file->private_data;
@ -138,8 +229,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
return len;
}
/* If we returned from read() last time because the Guest sent I/O,
* clear the flag. */
/*
* If we returned from read() last time because the Guest sent I/O,
* clear the flag.
*/
if (cpu->pending_notify)
cpu->pending_notify = 0;
@ -147,8 +240,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
return run_guest(cpu, (unsigned long __user *)user);
}
/*L:025 This actually initializes a CPU. For the moment, a Guest is only
* uniprocessor, so "id" is always 0. */
/*L:025
* This actually initializes a CPU. For the moment, a Guest is only
* uniprocessor, so "id" is always 0.
*/
static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
{
/* We have a limited number the number of CPUs in the lguest struct. */
@ -163,8 +258,10 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
/* Each CPU has a timer it can set. */
init_clockdev(cpu);
/* We need a complete page for the Guest registers: they are accessible
* to the Guest and we can only grant it access to whole pages. */
/*
* We need a complete page for the Guest registers: they are accessible
* to the Guest and we can only grant it access to whole pages.
*/
cpu->regs_page = get_zeroed_page(GFP_KERNEL);
if (!cpu->regs_page)
return -ENOMEM;
@ -172,29 +269,38 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
/* We actually put the registers at the bottom of the page. */
cpu->regs = (void *)cpu->regs_page + PAGE_SIZE - sizeof(*cpu->regs);
/* Now we initialize the Guest's registers, handing it the start
* address. */
/*
* Now we initialize the Guest's registers, handing it the start
* address.
*/
lguest_arch_setup_regs(cpu, start_ip);
/* We keep a pointer to the Launcher task (ie. current task) for when
* other Guests want to wake this one (eg. console input). */
/*
* We keep a pointer to the Launcher task (ie. current task) for when
* other Guests want to wake this one (eg. console input).
*/
cpu->tsk = current;
/* We need to keep a pointer to the Launcher's memory map, because if
/*
* We need to keep a pointer to the Launcher's memory map, because if
* the Launcher dies we need to clean it up. If we don't keep a
* reference, it is destroyed before close() is called. */
* reference, it is destroyed before close() is called.
*/
cpu->mm = get_task_mm(cpu->tsk);
/* We remember which CPU's pages this Guest used last, for optimization
* when the same Guest runs on the same CPU twice. */
/*
* We remember which CPU's pages this Guest used last, for optimization
* when the same Guest runs on the same CPU twice.
*/
cpu->last_pages = NULL;
/* No error == success. */
return 0;
}
/*L:020 The initialization write supplies 3 pointer sized (32 or 64 bit)
* values (in addition to the LHREQ_INITIALIZE value). These are:
/*L:020
* The initialization write supplies 3 pointer sized (32 or 64 bit) values (in
* addition to the LHREQ_INITIALIZE value). These are:
*
* base: The start of the Guest-physical memory inside the Launcher memory.
*
@ -206,14 +312,15 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
*/
static int initialize(struct file *file, const unsigned long __user *input)
{
/* "struct lguest" contains everything we (the Host) know about a
* Guest. */
/* "struct lguest" contains all we (the Host) know about a Guest. */
struct lguest *lg;
int err;
unsigned long args[3];
/* We grab the Big Lguest lock, which protects against multiple
* simultaneous initializations. */
/*
* We grab the Big Lguest lock, which protects against multiple
* simultaneous initializations.
*/
mutex_lock(&lguest_lock);
/* You can't initialize twice! Close the device and start again... */
if (file->private_data) {
@ -248,8 +355,10 @@ static int initialize(struct file *file, const unsigned long __user *input)
if (err)
goto free_eventfds;
/* Initialize the Guest's shadow page tables, using the toplevel
* address the Launcher gave us. This allocates memory, so can fail. */
/*
* Initialize the Guest's shadow page tables, using the toplevel
* address the Launcher gave us. This allocates memory, so can fail.
*/
err = init_guest_pagetable(lg);
if (err)
goto free_regs;
@ -274,20 +383,24 @@ unlock:
return err;
}
/*L:010 The first operation the Launcher does must be a write. All writes
/*L:010
* The first operation the Launcher does must be a write. All writes
* start with an unsigned long number: for the first write this must be
* LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
* writes of other values to send interrupts.
* writes of other values to send interrupts or set up receipt of notifications.
*
* Note that we overload the "offset" in the /dev/lguest file to indicate what
* CPU number we're dealing with. Currently this is always 0, since we only
* CPU number we're dealing with. Currently this is always 0 since we only
* support uniprocessor Guests, but you can see the beginnings of SMP support
* here. */
* here.
*/
static ssize_t write(struct file *file, const char __user *in,
size_t size, loff_t *off)
{
/* Once the Guest is initialized, we hold the "struct lguest" in the
* file private data. */
/*
* Once the Guest is initialized, we hold the "struct lguest" in the
* file private data.
*/
struct lguest *lg = file->private_data;
const unsigned long __user *input = (const unsigned long __user *)in;
unsigned long req;
@ -322,13 +435,15 @@ static ssize_t write(struct file *file, const char __user *in,
}
}
/*L:060 The final piece of interface code is the close() routine. It reverses
/*L:060
* The final piece of interface code is the close() routine. It reverses
* everything done in initialize(). This is usually called because the
* Launcher exited.
*
* Note that the close routine returns 0 or a negative error number: it can't
* really fail, but it can whine. I blame Sun for this wart, and K&R C for
* letting them do it. :*/
* letting them do it.
:*/
static int close(struct inode *inode, struct file *file)
{
struct lguest *lg = file->private_data;
@ -338,8 +453,10 @@ static int close(struct inode *inode, struct file *file)
if (!lg)
return 0;
/* We need the big lock, to protect from inter-guest I/O and other
* Launchers initializing guests. */
/*
* We need the big lock, to protect from inter-guest I/O and other
* Launchers initializing guests.
*/
mutex_lock(&lguest_lock);
/* Free up the shadow page tables for the Guest. */
@ -350,8 +467,10 @@ static int close(struct inode *inode, struct file *file)
hrtimer_cancel(&lg->cpus[i].hrt);
/* We can free up the register page we allocated. */
free_page(lg->cpus[i].regs_page);
/* Now all the memory cleanups are done, it's safe to release
* the Launcher's memory management structure. */
/*
* Now all the memory cleanups are done, it's safe to release
* the Launcher's memory management structure.
*/
mmput(lg->cpus[i].mm);
}
@ -360,8 +479,10 @@ static int close(struct inode *inode, struct file *file)
eventfd_ctx_put(lg->eventfds->map[i].event);
kfree(lg->eventfds);
/* If lg->dead doesn't contain an error code it will be NULL or a
* kmalloc()ed string, either of which is ok to hand to kfree(). */
/*
* If lg->dead doesn't contain an error code it will be NULL or a
* kmalloc()ed string, either of which is ok to hand to kfree().
*/
if (!IS_ERR(lg->dead))
kfree(lg->dead);
/* Free the memory allocated to the lguest_struct */
@ -385,7 +506,8 @@ static int close(struct inode *inode, struct file *file)
*
* We begin our understanding with the Host kernel interface which the Launcher
* uses: reading and writing a character device called /dev/lguest. All the
* work happens in the read(), write() and close() routines: */
* work happens in the read(), write() and close() routines:
*/
static struct file_operations lguest_fops = {
.owner = THIS_MODULE,
.release = close,
@ -393,8 +515,10 @@ static struct file_operations lguest_fops = {
.read = read,
};
/* This is a textbook example of a "misc" character device. Populate a "struct
* miscdevice" and register it with misc_register(). */
/*
* This is a textbook example of a "misc" character device. Populate a "struct
* miscdevice" and register it with misc_register().
*/
static struct miscdevice lguest_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = "lguest",

489
drivers/lguest/page_tables.c
View File

File diff suppressed because it is too large Load Diff

106
drivers/lguest/segments.c
View File

@ -1,4 +1,5 @@
/*P:600 The x86 architecture has segments, which involve a table of descriptors
/*P:600
* The x86 architecture has segments, which involve a table of descriptors
* which can be used to do funky things with virtual address interpretation.
* We originally used to use segments so the Guest couldn't alter the
* Guest<->Host Switcher, and then we had to trim Guest segments, and restore
@ -8,7 +9,8 @@
*
* In these modern times, the segment handling code consists of simple sanity
* checks, and the worst you'll experience reading this code is butterfly-rash
* from frolicking through its parklike serenity. :*/
* from frolicking through its parklike serenity.
:*/
#include "lg.h"
/*H:600
@ -41,10 +43,12 @@
* begin.
*/
/* There are several entries we don't let the Guest set. The TSS entry is the
/*
* There are several entries we don't let the Guest set. The TSS entry is the
* "Task State Segment" which controls all kinds of delicate things. The
* LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the
* the Guest can't be trusted to deal with double faults. */
* the Guest can't be trusted to deal with double faults.
*/
static bool ignored_gdt(unsigned int num)
{
return (num == GDT_ENTRY_TSS
@ -53,42 +57,52 @@ static bool ignored_gdt(unsigned int num)
|| num == GDT_ENTRY_DOUBLEFAULT_TSS);
}
/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We
/*H:630
* Once the Guest gave us new GDT entries, we fix them up a little. We
* don't care if they're invalid: the worst that can happen is a General
* Protection Fault in the Switcher when it restores a Guest segment register
* which tries to use that entry. Then we kill the Guest for causing such a
* mess: the message will be "unhandled trap 256". */
* mess: the message will be "unhandled trap 256".
*/
static void fixup_gdt_table(struct lg_cpu *cpu, unsigned start, unsigned end)
{
unsigned int i;
for (i = start; i < end; i++) {
/* We never copy these ones to real GDT, so we don't care what
* they say */
/*
* We never copy these ones to real GDT, so we don't care what
* they say
*/
if (ignored_gdt(i))
continue;
/* Segment descriptors contain a privilege level: the Guest is
/*
* Segment descriptors contain a privilege level: the Guest is
* sometimes careless and leaves this as 0, even though it's
* running at privilege level 1. If so, we fix it here. */
* running at privilege level 1. If so, we fix it here.
*/
if ((cpu->arch.gdt[i].b & 0x00006000) == 0)
cpu->arch.gdt[i].b |= (GUEST_PL << 13);
/* Each descriptor has an "accessed" bit. If we don't set it
/*
* Each descriptor has an "accessed" bit. If we don't set it
* now, the CPU will try to set it when the Guest first loads
* that entry into a segment register. But the GDT isn't
* writable by the Guest, so bad things can happen. */
* writable by the Guest, so bad things can happen.
*/
cpu->arch.gdt[i].b |= 0x00000100;
}
}
/*H:610 Like the IDT, we never simply use the GDT the Guest gives us. We keep
/*H:610
* Like the IDT, we never simply use the GDT the Guest gives us. We keep
* a GDT for each CPU, and copy across the Guest's entries each time we want to
* run the Guest on that CPU.
*
* This routine is called at boot or modprobe time for each CPU to set up the
* constant GDT entries: the ones which are the same no matter what Guest we're
* running. */
* running.
*/
void setup_default_gdt_entries(struct lguest_ro_state *state)
{
struct desc_struct *gdt = state->guest_gdt;
@ -98,30 +112,37 @@ void setup_default_gdt_entries(struct lguest_ro_state *state)
gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
/* The TSS segment refers to the TSS entry for this particular CPU.
/*
* The TSS segment refers to the TSS entry for this particular CPU.
* Forgive the magic flags: the 0x8900 means the entry is Present, it's
* privilege level 0 Available 386 TSS system segment, and the 0x67
* means Saturn is eclipsed by Mercury in the twelfth house. */
* means Saturn is eclipsed by Mercury in the twelfth house.
*/
gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
| ((tss >> 16) & 0x000000FF);
}
/* This routine sets up the initial Guest GDT for booting. All entries start
* as 0 (unusable). */
/*
* This routine sets up the initial Guest GDT for booting. All entries start
* as 0 (unusable).
*/
void setup_guest_gdt(struct lg_cpu *cpu)
{
/* Start with full 0-4G segments... */
/*
* Start with full 0-4G segments...except the Guest is allowed to use
* them, so set the privilege level appropriately in the flags.
*/
cpu->arch.gdt[GDT_ENTRY_KERNEL_CS] = FULL_EXEC_SEGMENT;
cpu->arch.gdt[GDT_ENTRY_KERNEL_DS] = FULL_SEGMENT;
/* ...except the Guest is allowed to use them, so set the privilege
* level appropriately in the flags. */
cpu->arch.gdt[GDT_ENTRY_KERNEL_CS].b |= (GUEST_PL << 13);
cpu->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
}
/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage"
* entries. */
/*H:650
* An optimization of copy_gdt(), for just the three "thead-local storage"
* entries.
*/
void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt)
{
unsigned int i;
@ -130,26 +151,34 @@ void copy_gdt_tls(const struct lg_cpu *cpu, struct desc_struct *gdt)
gdt[i] = cpu->arch.gdt[i];
}
/*H:640 When the Guest is run on a different CPU, or the GDT entries have
* changed, copy_gdt() is called to copy the Guest's GDT entries across to this
* CPU's GDT. */
/*H:640
* When the Guest is run on a different CPU, or the GDT entries have changed,
* copy_gdt() is called to copy the Guest's GDT entries across to this CPU's
* GDT.
*/
void copy_gdt(const struct lg_cpu *cpu, struct desc_struct *gdt)
{
unsigned int i;
/* The default entries from setup_default_gdt_entries() are not
* replaced. See ignored_gdt() above. */
/*
* The default entries from setup_default_gdt_entries() are not
* replaced. See ignored_gdt() above.
*/
for (i = 0; i < GDT_ENTRIES; i++)
if (!ignored_gdt(i))
gdt[i] = cpu->arch.gdt[i];
}
/*H:620 This is where the Guest asks us to load a new GDT entry
* (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in. */
/*H:620
* This is where the Guest asks us to load a new GDT entry
* (LHCALL_LOAD_GDT_ENTRY). We tweak the entry and copy it in.
*/
void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
{
/* We assume the Guest has the same number of GDT entries as the
* Host, otherwise we'd have to dynamically allocate the Guest GDT. */
/*
* We assume the Guest has the same number of GDT entries as the
* Host, otherwise we'd have to dynamically allocate the Guest GDT.
*/
if (num >= ARRAY_SIZE(cpu->arch.gdt))
kill_guest(cpu, "too many gdt entries %i", num);
@ -157,15 +186,19 @@ void load_guest_gdt_entry(struct lg_cpu *cpu, u32 num, u32 lo, u32 hi)
cpu->arch.gdt[num].a = lo;
cpu->arch.gdt[num].b = hi;
fixup_gdt_table(cpu, num, num+1);
/* Mark that the GDT changed so the core knows it has to copy it again,
* even if the Guest is run on the same CPU. */
/*
* Mark that the GDT changed so the core knows it has to copy it again,
* even if the Guest is run on the same CPU.
*/
cpu->changed |= CHANGED_GDT;
}
/* This is the fast-track version for just changing the three TLS entries.
/*
* This is the fast-track version for just changing the three TLS entries.
* Remember that this happens on every context switch, so it's worth
* optimizing. But wouldn't it be neater to have a single hypercall to cover
* both cases? */
* both cases?
*/
void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls)
{
struct desc_struct *tls = &cpu->arch.gdt[GDT_ENTRY_TLS_MIN];
@ -175,7 +208,6 @@ void guest_load_tls(struct lg_cpu *cpu, unsigned long gtls)
/* Note that just the TLS entries have changed. */
cpu->changed |= CHANGED_GDT_TLS;
}
/*:*/
/*H:660
* With this, we have finished the Host.

374
drivers/lguest/x86/core.c
View File

@ -17,13 +17,15 @@
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*P:450 This file contains the x86-specific lguest code. It used to be all
/*P:450
* This file contains the x86-specific lguest code. It used to be all
* mixed in with drivers/lguest/core.c but several foolhardy code slashers
* wrestled most of the dependencies out to here in preparation for porting
* lguest to other architectures (see what I mean by foolhardy?).
*
* This also contains a couple of non-obvious setup and teardown pieces which
* were implemented after days of debugging pain. :*/
* were implemented after days of debugging pain.
:*/
#include <linux/kernel.h>
#include <linux/start_kernel.h>
#include <linux/string.h>
@ -82,25 +84,33 @@ static DEFINE_PER_CPU(struct lg_cpu *, last_cpu);
*/
static void copy_in_guest_info(struct lg_cpu *cpu, struct lguest_pages *pages)
{
/* Copying all this data can be quite expensive. We usually run the
/*
* Copying all this data can be quite expensive. We usually run the
* same Guest we ran last time (and that Guest hasn't run anywhere else
* meanwhile). If that's not the case, we pretend everything in the
* Guest has changed. */
* Guest has changed.
*/
if (__get_cpu_var(last_cpu) != cpu || cpu->last_pages != pages) {
__get_cpu_var(last_cpu) = cpu;
cpu->last_pages = pages;
cpu->changed = CHANGED_ALL;
}
/* These copies are pretty cheap, so we do them unconditionally: */
/* Save the current Host top-level page directory. */
/*
* These copies are pretty cheap, so we do them unconditionally: */
/* Save the current Host top-level page directory.
*/
pages->state.host_cr3 = __pa(current->mm->pgd);
/* Set up the Guest's page tables to see this CPU's pages (and no
* other CPU's pages). */
/*
* Set up the Guest's page tables to see this CPU's pages (and no
* other CPU's pages).
*/
map_switcher_in_guest(cpu, pages);
/* Set up the two "TSS" members which tell the CPU what stack to use
/*
* Set up the two "TSS" members which tell the CPU what stack to use
* for traps which do directly into the Guest (ie. traps at privilege
* level 1). */
* level 1).
*/
pages->state.guest_tss.sp1 = cpu->esp1;
pages->state.guest_tss.ss1 = cpu->ss1;
@ -125,97 +135,126 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
/* This is a dummy value we need for GCC's sake. */
unsigned int clobber;
/* Copy the guest-specific information into this CPU's "struct
* lguest_pages". */
/*
* Copy the guest-specific information into this CPU's "struct
* lguest_pages".
*/
copy_in_guest_info(cpu, pages);
/* Set the trap number to 256 (impossible value). If we fault while
/*
* Set the trap number to 256 (impossible value). If we fault while
* switching to the Guest (bad segment registers or bug), this will
* cause us to abort the Guest. */
* cause us to abort the Guest.
*/
cpu->regs->trapnum = 256;
/* Now: we push the "eflags" register on the stack, then do an "lcall".
/*
* Now: we push the "eflags" register on the stack, then do an "lcall".
* This is how we change from using the kernel code segment to using
* the dedicated lguest code segment, as well as jumping into the
* Switcher.
*
* The lcall also pushes the old code segment (KERNEL_CS) onto the
* stack, then the address of this call. This stack layout happens to
* exactly match the stack layout created by an interrupt... */
* exactly match the stack layout created by an interrupt...
*/
asm volatile("pushf; lcall *lguest_entry"
/* This is how we tell GCC that %eax ("a") and %ebx ("b")
* are changed by this routine. The "=" means output. */
/*
* This is how we tell GCC that %eax ("a") and %ebx ("b")
* are changed by this routine. The "=" means output.
*/
: "=a"(clobber), "=b"(clobber)
/* %eax contains the pages pointer. ("0" refers to the
/*
* %eax contains the pages pointer. ("0" refers to the
* 0-th argument above, ie "a"). %ebx contains the
* physical address of the Guest's top-level page
* directory. */
* directory.
*/
: "0"(pages), "1"(__pa(cpu->lg->pgdirs[cpu->cpu_pgd].pgdir))
/* We tell gcc that all these registers could change,
/*
* We tell gcc that all these registers could change,
* which means we don't have to save and restore them in
* the Switcher. */
* the Switcher.
*/
: "memory", "%edx", "%ecx", "%edi", "%esi");
}
/*:*/
/*M:002 There are hooks in the scheduler which we can register to tell when we
/*M:002
* There are hooks in the scheduler which we can register to tell when we
* get kicked off the CPU (preempt_notifier_register()). This would allow us
* to lazily disable SYSENTER which would regain some performance, and should
* also simplify copy_in_guest_info(). Note that we'd still need to restore
* things when we exit to Launcher userspace, but that's fairly easy.
*
* We could also try using this hooks for PGE, but that might be too expensive.
* We could also try using these hooks for PGE, but that might be too expensive.
*
* The hooks were designed for KVM, but we can also put them to good use. :*/
* The hooks were designed for KVM, but we can also put them to good use.
:*/
/*H:040 This is the i386-specific code to setup and run the Guest. Interrupts
* are disabled: we own the CPU. */
/*H:040
* This is the i386-specific code to setup and run the Guest. Interrupts
* are disabled: we own the CPU.
*/
void lguest_arch_run_guest(struct lg_cpu *cpu)
{
/* Remember the awfully-named TS bit? If the Guest has asked to set it
/*
* Remember the awfully-named TS bit? If the Guest has asked to set it
* we set it now, so we can trap and pass that trap to the Guest if it
* uses the FPU. */
* uses the FPU.
*/
if (cpu->ts)
unlazy_fpu(current);
/* SYSENTER is an optimized way of doing system calls. We can't allow
/*
* SYSENTER is an optimized way of doing system calls. We can't allow
* it because it always jumps to privilege level 0. A normal Guest
* won't try it because we don't advertise it in CPUID, but a malicious
* Guest (or malicious Guest userspace program) could, so we tell the
* CPU to disable it before running the Guest. */
* CPU to disable it before running the Guest.
*/
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
/* Now we actually run the Guest. It will return when something
/*
* Now we actually run the Guest. It will return when something
* interesting happens, and we can examine its registers to see what it
* was doing. */
* was doing.
*/
run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));
/* Note that the "regs" structure contains two extra entries which are
/*
* Note that the "regs" structure contains two extra entries which are
* not really registers: a trap number which says what interrupt or
* trap made the switcher code come back, and an error code which some
* traps set. */
* traps set.
*/
/* Restore SYSENTER if it's supposed to be on. */
if (boot_cpu_has(X86_FEATURE_SEP))
wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
/* If the Guest page faulted, then the cr2 register will tell us the
/*
* If the Guest page faulted, then the cr2 register will tell us the
* bad virtual address. We have to grab this now, because once we
* re-enable interrupts an interrupt could fault and thus overwrite
* cr2, or we could even move off to a different CPU. */
* cr2, or we could even move off to a different CPU.
*/
if (cpu->regs->trapnum == 14)
cpu->arch.last_pagefault = read_cr2();
/* Similarly, if we took a trap because the Guest used the FPU,
/*
* Similarly, if we took a trap because the Guest used the FPU,
* we have to restore the FPU it expects to see.
* math_state_restore() may sleep and we may even move off to
* a different CPU. So all the critical stuff should be done
* before this. */
* before this.
*/
else if (cpu->regs->trapnum == 7)
math_state_restore();
}
/*H:130 Now we've examined the hypercall code; our Guest can make requests.
/*H:130
* Now we've examined the hypercall code; our Guest can make requests.
* Our Guest is usually so well behaved; it never tries to do things it isn't
* allowed to, and uses hypercalls instead. Unfortunately, Linux's paravirtual
* infrastructure isn't quite complete, because it doesn't contain replacements
@ -225,26 +264,33 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
*
* When the Guest uses one of these instructions, we get a trap (General
* Protection Fault) and come here. We see if it's one of those troublesome
* instructions and skip over it. We return true if we did. */
* instructions and skip over it. We return true if we did.
*/
static int emulate_insn(struct lg_cpu *cpu)
{
u8 insn;
unsigned int insnlen = 0, in = 0, shift = 0;
/* The eip contains the *virtual* address of the Guest's instruction:
* guest_pa just subtracts the Guest's page_offset. */
/*
* The eip contains the *virtual* address of the Guest's instruction:
* guest_pa just subtracts the Guest's page_offset.
*/
unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
/* This must be the Guest kernel trying to do something, not userspace!
/*
* This must be the Guest kernel trying to do something, not userspace!
* The bottom two bits of the CS segment register are the privilege
* level. */
* level.
*/
if ((cpu->regs->cs & 3) != GUEST_PL)
return 0;
/* Decoding x86 instructions is icky. */
insn = lgread(cpu, physaddr, u8);
/* 0x66 is an "operand prefix". It means it's using the upper 16 bits
of the eax register. */
/*
* 0x66 is an "operand prefix". It means it's using the upper 16 bits
* of the eax register.
*/
if (insn == 0x66) {
shift = 16;
/* The instruction is 1 byte so far, read the next byte. */
@ -252,8 +298,10 @@ static int emulate_insn(struct lg_cpu *cpu)
insn = lgread(cpu, physaddr + insnlen, u8);
}
/* We can ignore the lower bit for the moment and decode the 4 opcodes
* we need to emulate. */
/*
* We can ignore the lower bit for the moment and decode the 4 opcodes
* we need to emulate.
*/
switch (insn & 0xFE) {
case 0xE4: /* in <next byte>,%al */
insnlen += 2;
@ -274,9 +322,11 @@ static int emulate_insn(struct lg_cpu *cpu)
return 0;
}
/* If it was an "IN" instruction, they expect the result to be read
/*
* If it was an "IN" instruction, they expect the result to be read
* into %eax, so we change %eax. We always return all-ones, which
* traditionally means "there's nothing there". */
* traditionally means "there's nothing there".
*/
if (in) {
/* Lower bit tells is whether it's a 16 or 32 bit access */
if (insn & 0x1)
@ -290,7 +340,8 @@ static int emulate_insn(struct lg_cpu *cpu)
return 1;
}
/* Our hypercalls mechanism used to be based on direct software interrupts.
/*
* Our hypercalls mechanism used to be based on direct software interrupts.
* After Anthony's "Refactor hypercall infrastructure" kvm patch, we decided to
* change over to using kvm hypercalls.
*
@ -318,16 +369,20 @@ static int emulate_insn(struct lg_cpu *cpu)
*/
static void rewrite_hypercall(struct lg_cpu *cpu)
{
/* This are the opcodes we use to patch the Guest. The opcode for "int
/*
* This are the opcodes we use to patch the Guest. The opcode for "int
* $0x1f" is "0xcd 0x1f" but vmcall instruction is 3 bytes long, so we
* complete the sequence with a NOP (0x90). */
* complete the sequence with a NOP (0x90).
*/
u8 insn[3] = {0xcd, 0x1f, 0x90};
__lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));
/* The above write might have caused a copy of that page to be made
/*
* The above write might have caused a copy of that page to be made
* (if it was read-only). We need to make sure the Guest has
* up-to-date pagetables. As this doesn't happen often, we can just
* drop them all. */
* drop them all.
*/
guest_pagetable_clear_all(cpu);
}
@ -335,9 +390,11 @@ static bool is_hypercall(struct lg_cpu *cpu)
{
u8 insn[3];
/* This must be the Guest kernel trying to do something.
/*
* This must be the Guest kernel trying to do something.
* The bottom two bits of the CS segment register are the privilege
* level. */
* level.
*/
if ((cpu->regs->cs & 3) != GUEST_PL)
return false;
@ -351,86 +408,105 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
{
switch (cpu->regs->trapnum) {
case 13: /* We've intercepted a General Protection Fault. */
/* Check if this was one of those annoying IN or OUT
/*
* Check if this was one of those annoying IN or OUT
* instructions which we need to emulate. If so, we just go
* back into the Guest after we've done it. */
* back into the Guest after we've done it.
*/
if (cpu->regs->errcode == 0) {
if (emulate_insn(cpu))
return;
}
/* If KVM is active, the vmcall instruction triggers a
* General Protection Fault. Normally it triggers an
* invalid opcode fault (6): */
/*
* If KVM is active, the vmcall instruction triggers a General
* Protection Fault. Normally it triggers an invalid opcode
* fault (6):
*/
case 6:
/* We need to check if ring == GUEST_PL and
* faulting instruction == vmcall. */
/*
* We need to check if ring == GUEST_PL and faulting
* instruction == vmcall.
*/
if (is_hypercall(cpu)) {
rewrite_hypercall(cpu);
return;
}
break;
case 14: /* We've intercepted a Page Fault. */
/* The Guest accessed a virtual address that wasn't mapped.
/*
* The Guest accessed a virtual address that wasn't mapped.
* This happens a lot: we don't actually set up most of the page
* tables for the Guest at all when we start: as it runs it asks
* for more and more, and we set them up as required. In this
* case, we don't even tell the Guest that the fault happened.
*
* The errcode tells whether this was a read or a write, and
* whether kernel or userspace code. */
* whether kernel or userspace code.
*/
if (demand_page(cpu, cpu->arch.last_pagefault,
cpu->regs->errcode))
return;
/* OK, it's really not there (or not OK): the Guest needs to
/*
* OK, it's really not there (or not OK): the Guest needs to
* know. We write out the cr2 value so it knows where the
* fault occurred.
*
* Note that if the Guest were really messed up, this could
* happen before it's done the LHCALL_LGUEST_INIT hypercall, so
* lg->lguest_data could be NULL */
* lg->lguest_data could be NULL
*/
if (cpu->lg->lguest_data &&
put_user(cpu->arch.last_pagefault,
&cpu->lg->lguest_data->cr2))
kill_guest(cpu, "Writing cr2");
break;
case 7: /* We've intercepted a Device Not Available fault. */
/* If the Guest doesn't want to know, we already restored the
* Floating Point Unit, so we just continue without telling
* it. */
/*
* If the Guest doesn't want to know, we already restored the
* Floating Point Unit, so we just continue without telling it.
*/
if (!cpu->ts)
return;
break;
case 32 ... 255:
/* These values mean a real interrupt occurred, in which case
/*
* These values mean a real interrupt occurred, in which case
* the Host handler has already been run. We just do a
* friendly check if another process should now be run, then
* return to run the Guest again */
* return to run the Guest again
*/
cond_resched();
return;
case LGUEST_TRAP_ENTRY:
/* Our 'struct hcall_args' maps directly over our regs: we set
* up the pointer now to indicate a hypercall is pending. */
/*
* Our 'struct hcall_args' maps directly over our regs: we set
* up the pointer now to indicate a hypercall is pending.
*/
cpu->hcall = (struct hcall_args *)cpu->regs;
return;
}
/* We didn't handle the trap, so it needs to go to the Guest. */
if (!deliver_trap(cpu, cpu->regs->trapnum))
/* If the Guest doesn't have a handler (either it hasn't
/*
* If the Guest doesn't have a handler (either it hasn't
* registered any yet, or it's one of the faults we don't let
* it handle), it dies with this cryptic error message. */
* it handle), it dies with this cryptic error message.
*/
kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)",
cpu->regs->trapnum, cpu->regs->eip,
cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault
: cpu->regs->errcode);
}
/* Now we can look at each of the routines this calls, in increasing order of
/*
* Now we can look at each of the routines this calls, in increasing order of
* complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(),
* deliver_trap() and demand_page(). After all those, we'll be ready to
* examine the Switcher, and our philosophical understanding of the Host/Guest
* duality will be complete. :*/
* duality will be complete.
:*/
static void adjust_pge(void *on)
{
if (on)
@ -439,13 +515,16 @@ static void adjust_pge(void *on)
write_cr4(read_cr4() & ~X86_CR4_PGE);
}
/*H:020 Now the Switcher is mapped and every thing else is ready, we need to do
* some more i386-specific initialization. */
/*H:020
* Now the Switcher is mapped and every thing else is ready, we need to do
* some more i386-specific initialization.
*/
void __init lguest_arch_host_init(void)
{
int i;
/* Most of the i386/switcher.S doesn't care that it's been moved; on
/*
* Most of the i386/switcher.S doesn't care that it's been moved; on
* Intel, jumps are relative, and it doesn't access any references to
* external code or data.
*
@ -453,7 +532,8 @@ void __init lguest_arch_host_init(void)
* addresses are placed in a table (default_idt_entries), so we need to
* update the table with the new addresses. switcher_offset() is a
* convenience function which returns the distance between the
* compiled-in switcher code and the high-mapped copy we just made. */
* compiled-in switcher code and the high-mapped copy we just made.
*/
for (i = 0; i < IDT_ENTRIES; i++)
default_idt_entries[i] += switcher_offset();
@ -468,63 +548,81 @@ void __init lguest_arch_host_init(void)
for_each_possible_cpu(i) {
/* lguest_pages() returns this CPU's two pages. */
struct lguest_pages *pages = lguest_pages(i);
/* This is a convenience pointer to make the code fit one
* statement to a line. */
/* This is a convenience pointer to make the code neater. */
struct lguest_ro_state *state = &pages->state;
/* The Global Descriptor Table: the Host has a different one
/*
* The Global Descriptor Table: the Host has a different one
* for each CPU. We keep a descriptor for the GDT which says
* where it is and how big it is (the size is actually the last
* byte, not the size, hence the "-1"). */
* byte, not the size, hence the "-1").
*/
state->host_gdt_desc.size = GDT_SIZE-1;
state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);
/* All CPUs on the Host use the same Interrupt Descriptor
/*
* All CPUs on the Host use the same Interrupt Descriptor
* Table, so we just use store_idt(), which gets this CPU's IDT
* descriptor. */
* descriptor.
*/
store_idt(&state->host_idt_desc);
/* The descriptors for the Guest's GDT and IDT can be filled
/*
* The descriptors for the Guest's GDT and IDT can be filled
* out now, too. We copy the GDT & IDT into ->guest_gdt and
* ->guest_idt before actually running the Guest. */
* ->guest_idt before actually running the Guest.
*/
state->guest_idt_desc.size = sizeof(state->guest_idt)-1;
state->guest_idt_desc.address = (long)&state->guest_idt;
state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1;
state->guest_gdt_desc.address = (long)&state->guest_gdt;
/* We know where we want the stack to be when the Guest enters
/*
* We know where we want the stack to be when the Guest enters
* the Switcher: in pages->regs. The stack grows upwards, so
* we start it at the end of that structure. */
* we start it at the end of that structure.
*/
state->guest_tss.sp0 = (long)(&pages->regs + 1);
/* And this is the GDT entry to use for the stack: we keep a
* couple of special LGUEST entries. */
/*
* And this is the GDT entry to use for the stack: we keep a
* couple of special LGUEST entries.
*/
state->guest_tss.ss0 = LGUEST_DS;
/* x86 can have a finegrained bitmap which indicates what I/O
/*
* x86 can have a finegrained bitmap which indicates what I/O
* ports the process can use. We set it to the end of our
* structure, meaning "none". */
* structure, meaning "none".
*/
state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);
/* Some GDT entries are the same across all Guests, so we can
* set them up now. */
/*
* Some GDT entries are the same across all Guests, so we can
* set them up now.
*/
setup_default_gdt_entries(state);
/* Most IDT entries are the same for all Guests, too.*/
setup_default_idt_entries(state, default_idt_entries);
/* The Host needs to be able to use the LGUEST segments on this
* CPU, too, so put them in the Host GDT. */
/*
* The Host needs to be able to use the LGUEST segments on this
* CPU, too, so put them in the Host GDT.
*/
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
}
/* In the Switcher, we want the %cs segment register to use the
/*
* In the Switcher, we want the %cs segment register to use the
* LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so
* it will be undisturbed when we switch. To change %cs and jump we
* need this structure to feed to Intel's "lcall" instruction. */
* need this structure to feed to Intel's "lcall" instruction.
*/
lguest_entry.offset = (long)switch_to_guest + switcher_offset();
lguest_entry.segment = LGUEST_CS;
/* Finally, we need to turn off "Page Global Enable". PGE is an
/*
* Finally, we need to turn off "Page Global Enable". PGE is an
* optimization where page table entries are specially marked to show
* they never change. The Host kernel marks all the kernel pages this
* way because it's always present, even when userspace is running.
@ -534,16 +632,21 @@ void __init lguest_arch_host_init(void)
* you'll get really weird bugs that you'll chase for two days.
*
* I used to turn PGE off every time we switched to the Guest and back
* on when we return, but that slowed the Switcher down noticibly. */
* on when we return, but that slowed the Switcher down noticibly.
*/
/* We don't need the complexity of CPUs coming and going while we're
* doing this. */
/*
* We don't need the complexity of CPUs coming and going while we're
* doing this.
*/
get_online_cpus();
if (cpu_has_pge) { /* We have a broader idea of "global". */
/* Remember that this was originally set (for cleanup). */
cpu_had_pge = 1;
/* adjust_pge is a helper function which sets or unsets the PGE
* bit on its CPU, depending on the argument (0 == unset). */
/*
* adjust_pge is a helper function which sets or unsets the PGE
* bit on its CPU, depending on the argument (0 == unset).
*/
on_each_cpu(adjust_pge, (void *)0, 1);
/* Turn off the feature in the global feature set. */
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
@ -590,26 +693,32 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
{
u32 tsc_speed;
/* The pointer to the Guest's "struct lguest_data" is the only argument.
* We check that address now. */
/*
* The pointer to the Guest's "struct lguest_data" is the only argument.
* We check that address now.
*/
if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1,
sizeof(*cpu->lg->lguest_data)))
return -EFAULT;
/* Having checked it, we simply set lg->lguest_data to point straight
/*
* Having checked it, we simply set lg->lguest_data to point straight
* into the Launcher's memory at the right place and then use
* copy_to_user/from_user from now on, instead of lgread/write. I put
* this in to show that I'm not immune to writing stupid
* optimizations. */
* optimizations.
*/
cpu->lg->lguest_data = cpu->lg->mem_base + cpu->hcall->arg1;
/* We insist that the Time Stamp Counter exist and doesn't change with
/*
* We insist that the Time Stamp Counter exist and doesn't change with
* cpu frequency. Some devious chip manufacturers decided that TSC
* changes could be handled in software. I decided that time going
* backwards might be good for benchmarks, but it's bad for users.
*
* We also insist that the TSC be stable: the kernel detects unreliable
* TSCs for its own purposes, and we use that here. */
* TSCs for its own purposes, and we use that here.
*/
if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())
tsc_speed = tsc_khz;
else
@ -625,38 +734,47 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
}
/*:*/
/*L:030 lguest_arch_setup_regs()
/*L:030
* lguest_arch_setup_regs()
*
* Most of the Guest's registers are left alone: we used get_zeroed_page() to
* allocate the structure, so they will be 0. */
* allocate the structure, so they will be 0.
*/
void lguest_arch_setup_regs(struct lg_cpu *cpu, unsigned long start)
{
struct lguest_regs *regs = cpu->regs;
/* There are four "segment" registers which the Guest needs to boot:
/*
* There are four "segment" registers which the Guest needs to boot:
* The "code segment" register (cs) refers to the kernel code segment
* __KERNEL_CS, and the "data", "extra" and "stack" segment registers
* refer to the kernel data segment __KERNEL_DS.
*
* The privilege level is packed into the lower bits. The Guest runs
* at privilege level 1 (GUEST_PL).*/
* at privilege level 1 (GUEST_PL).
*/
regs->ds = regs->es = regs->ss = __KERNEL_DS|GUEST_PL;
regs->cs = __KERNEL_CS|GUEST_PL;
/* The "eflags" register contains miscellaneous flags. Bit 1 (0x002)
/*
* The "eflags" register contains miscellaneous flags. Bit 1 (0x002)
* is supposed to always be "1". Bit 9 (0x200) controls whether
* interrupts are enabled. We always leave interrupts enabled while
* running the Guest. */
* running the Guest.
*/
regs->eflags = X86_EFLAGS_IF | 0x2;
/* The "Extended Instruction Pointer" register says where the Guest is
* running. */
/*
* The "Extended Instruction Pointer" register says where the Guest is
* running.
*/
regs->eip = start;
/* %esi points to our boot information, at physical address 0, so don't
* touch it. */
/*
* %esi points to our boot information, at physical address 0, so don't
* touch it.
*/
/* There are a couple of GDT entries the Guest expects when first
* booting. */
/* There are a couple of GDT entries the Guest expects at boot. */
setup_guest_gdt(cpu);
}

22
drivers/lguest/x86/switcher_32.S
View File

@ -1,12 +1,15 @@
/*P:900 This is the Switcher: code which sits at 0xFFC00000 astride both the
* Host and Guest to do the low-level Guest<->Host switch. It is as simple as
* it can be made, but it's naturally very specific to x86.
/*P:900
* This is the Switcher: code which sits at 0xFFC00000 (or 0xFFE00000) astride
* both the Host and Guest to do the low-level Guest<->Host switch. It is as
* simple as it can be made, but it's naturally very specific to x86.
*
* You have now completed Preparation. If this has whet your appetite; if you
* are feeling invigorated and refreshed then the next, more challenging stage
* can be found in "make Guest". :*/
* can be found in "make Guest".
:*/
/*M:012 Lguest is meant to be simple: my rule of thumb is that 1% more LOC must
/*M:012
* Lguest is meant to be simple: my rule of thumb is that 1% more LOC must
* gain at least 1% more performance. Since neither LOC nor performance can be
* measured beforehand, it generally means implementing a feature then deciding
* if it's worth it. And once it's implemented, who can say no?
@ -31,11 +34,14 @@
* Host (which is actually really easy).
*
* Two questions remain. Would the performance gain outweigh the complexity?
* And who would write the verse documenting it? :*/
* And who would write the verse documenting it?
:*/
/*M:011 Lguest64 handles NMI. This gave me NMI envy (until I looked at their
/*M:011
* Lguest64 handles NMI. This gave me NMI envy (until I looked at their
* code). It's worth doing though, since it would let us use oprofile in the
* Host when a Guest is running. :*/
* Host when a Guest is running.
:*/
/*S:100
* Welcome to the Switcher itself!

254
drivers/virtio/virtio_pci.c
View File

@ -52,8 +52,10 @@ struct virtio_pci_device
char (*msix_names)[256];
/* Number of available vectors */
unsigned msix_vectors;
/* Vectors allocated */
/* Vectors allocated, excluding per-vq vectors if any */
unsigned msix_used_vectors;
/* Whether we have vector per vq */
bool per_vq_vectors;
};
/* Constants for MSI-X */
@ -258,7 +260,6 @@ static void vp_free_vectors(struct virtio_device *vdev)
for (i = 0; i < vp_dev->msix_used_vectors; ++i)
free_irq(vp_dev->msix_entries[i].vector, vp_dev);
vp_dev->msix_used_vectors = 0;
if (vp_dev->msix_enabled) {
/* Disable the vector used for configuration */
@ -267,80 +268,77 @@ static void vp_free_vectors(struct virtio_device *vdev)
/* Flush the write out to device */
ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
vp_dev->msix_enabled = 0;
pci_disable_msix(vp_dev->pci_dev);
vp_dev->msix_enabled = 0;
vp_dev->msix_vectors = 0;
}
vp_dev->msix_used_vectors = 0;
kfree(vp_dev->msix_names);
vp_dev->msix_names = NULL;
kfree(vp_dev->msix_entries);
vp_dev->msix_entries = NULL;
}
static int vp_enable_msix(struct pci_dev *dev, struct msix_entry *entries,
int *options, int noptions)
{
int i;
for (i = 0; i < noptions; ++i)
if (!pci_enable_msix(dev, entries, options[i]))
return options[i];
return -EBUSY;
}
static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)
static int vp_request_vectors(struct virtio_device *vdev, int nvectors,
bool per_vq_vectors)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
const char *name = dev_name(&vp_dev->vdev.dev);
unsigned i, v;
int err = -ENOMEM;
/* We want at most one vector per queue and one for config changes.
* Fallback to separate vectors for config and a shared for queues.
* Finally fall back to regular interrupts. */
int options[] = { max_vqs + 1, 2 };
int nvectors = max(options[0], options[1]);
vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
GFP_KERNEL);
if (!vp_dev->msix_entries)
goto error_entries;
vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names,
GFP_KERNEL);
if (!vp_dev->msix_names)
goto error_names;
for (i = 0; i < nvectors; ++i)
vp_dev->msix_entries[i].entry = i;
err = vp_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries,
options, ARRAY_SIZE(options));
if (err < 0) {
/* Can't allocate enough MSI-X vectors, use regular interrupt */
if (!nvectors) {
/* Can't allocate MSI-X vectors, use regular interrupt */
vp_dev->msix_vectors = 0;
err = request_irq(vp_dev->pci_dev->irq, vp_interrupt,
IRQF_SHARED, name, vp_dev);
if (err)
goto error_irq;
return err;
vp_dev->intx_enabled = 1;
} else {
vp_dev->msix_vectors = err;
vp_dev->msix_enabled = 1;
/* Set the vector used for configuration */
v = vp_dev->msix_used_vectors;
snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
"%s-config", name);
err = request_irq(vp_dev->msix_entries[v].vector,
vp_config_changed, 0, vp_dev->msix_names[v],
vp_dev);
if (err)
goto error_irq;
++vp_dev->msix_used_vectors;
iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
/* Verify we had enough resources to assign the vector */
v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
if (v == VIRTIO_MSI_NO_VECTOR) {
err = -EBUSY;
goto error_irq;
}
return 0;
}
if (vp_dev->msix_vectors && vp_dev->msix_vectors != max_vqs + 1) {
vp_dev->msix_entries = kmalloc(nvectors * sizeof *vp_dev->msix_entries,
GFP_KERNEL);
if (!vp_dev->msix_entries)
goto error;
vp_dev->msix_names = kmalloc(nvectors * sizeof *vp_dev->msix_names,
GFP_KERNEL);
if (!vp_dev->msix_names)
goto error;
for (i = 0; i < nvectors; ++i)
vp_dev->msix_entries[i].entry = i;
err = pci_enable_msix(vp_dev->pci_dev, vp_dev->msix_entries, nvectors);
if (err > 0)
err = -ENOSPC;
if (err)
goto error;
vp_dev->msix_vectors = nvectors;
vp_dev->msix_enabled = 1;
/* Set the vector used for configuration */
v = vp_dev->msix_used_vectors;
snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
"%s-config", name);
err = request_irq(vp_dev->msix_entries[v].vector,
vp_config_changed, 0, vp_dev->msix_names[v],
vp_dev);
if (err)
goto error;
++vp_dev->msix_used_vectors;
iowrite16(v, vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
/* Verify we had enough resources to assign the vector */
v = ioread16(vp_dev->ioaddr + VIRTIO_MSI_CONFIG_VECTOR);
if (v == VIRTIO_MSI_NO_VECTOR) {
err = -EBUSY;
goto error;
}
if (!per_vq_vectors) {
/* Shared vector for all VQs */
v = vp_dev->msix_used_vectors;
snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
@ -349,28 +347,25 @@ static int vp_request_vectors(struct virtio_device *vdev, unsigned max_vqs)
vp_vring_interrupt, 0, vp_dev->msix_names[v],
vp_dev);
if (err)
goto error_irq;
goto error;
++vp_dev->msix_used_vectors;
}
return 0;
error_irq:
error:
vp_free_vectors(vdev);
kfree(vp_dev->msix_names);
error_names:
kfree(vp_dev->msix_entries);
error_entries:
return err;
}
static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
void (*callback)(struct virtqueue *vq),
const char *name)
const char *name,
u16 vector)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtio_pci_vq_info *info;
struct virtqueue *vq;
unsigned long flags, size;
u16 num, vector;
u16 num;
int err;
/* Select the queue we're interested in */
@ -389,7 +384,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
info->queue_index = index;
info->num = num;
info->vector = VIRTIO_MSI_NO_VECTOR;
info->vector = vector;
size = PAGE_ALIGN(vring_size(num, VIRTIO_PCI_VRING_ALIGN));
info->queue = alloc_pages_exact(size, GFP_KERNEL|__GFP_ZERO);
@ -413,22 +408,7 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
vq->priv = info;
info->vq = vq;
/* allocate per-vq vector if available and necessary */
if (callback && vp_dev->msix_used_vectors < vp_dev->msix_vectors) {
vector = vp_dev->msix_used_vectors;
snprintf(vp_dev->msix_names[vector], sizeof *vp_dev->msix_names,
"%s-%s", dev_name(&vp_dev->vdev.dev), name);
err = request_irq(vp_dev->msix_entries[vector].vector,
vring_interrupt, 0,
vp_dev->msix_names[vector], vq);
if (err)
goto out_request_irq;
info->vector = vector;
++vp_dev->msix_used_vectors;
} else
vector = VP_MSIX_VQ_VECTOR;
if (callback && vp_dev->msix_enabled) {
if (vector != VIRTIO_MSI_NO_VECTOR) {
iowrite16(vector, vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
vector = ioread16(vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
if (vector == VIRTIO_MSI_NO_VECTOR) {
@ -444,11 +424,6 @@ static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
return vq;
out_assign:
if (info->vector != VIRTIO_MSI_NO_VECTOR) {
free_irq(vp_dev->msix_entries[info->vector].vector, vq);
--vp_dev->msix_used_vectors;
}
out_request_irq:
vring_del_virtqueue(vq);
out_activate_queue:
iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
@ -462,13 +437,14 @@ static void vp_del_vq(struct virtqueue *vq)
{
struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
struct virtio_pci_vq_info *info = vq->priv;
unsigned long size;
unsigned long flags, size;
spin_lock_irqsave(&vp_dev->lock, flags);
list_del(&info->node);
spin_unlock_irqrestore(&vp_dev->lock, flags);
iowrite16(info->queue_index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
if (info->vector != VIRTIO_MSI_NO_VECTOR)
free_irq(vp_dev->msix_entries[info->vector].vector, vq);
if (vp_dev->msix_enabled) {
iowrite16(VIRTIO_MSI_NO_VECTOR,
vp_dev->ioaddr + VIRTIO_MSI_QUEUE_VECTOR);
@ -489,14 +465,72 @@ static void vp_del_vq(struct virtqueue *vq)
/* the config->del_vqs() implementation */
static void vp_del_vqs(struct virtio_device *vdev)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
struct virtqueue *vq, *n;
struct virtio_pci_vq_info *info;
list_for_each_entry_safe(vq, n, &vdev->vqs, list)
list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
info = vq->priv;
if (vp_dev->per_vq_vectors)
free_irq(vp_dev->msix_entries[info->vector].vector, vq);
vp_del_vq(vq);
}
vp_dev->per_vq_vectors = false;
vp_free_vectors(vdev);
}
static int vp_try_to_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
vq_callback_t *callbacks[],
const char *names[],
int nvectors,
bool per_vq_vectors)
{
struct virtio_pci_device *vp_dev = to_vp_device(vdev);
u16 vector;
int i, err, allocated_vectors;
err = vp_request_vectors(vdev, nvectors, per_vq_vectors);
if (err)
goto error_request;
vp_dev->per_vq_vectors = per_vq_vectors;
allocated_vectors = vp_dev->msix_used_vectors;
for (i = 0; i < nvqs; ++i) {
if (!callbacks[i] || !vp_dev->msix_enabled)
vector = VIRTIO_MSI_NO_VECTOR;
else if (vp_dev->per_vq_vectors)
vector = allocated_vectors++;
else
vector = VP_MSIX_VQ_VECTOR;
vqs[i] = vp_find_vq(vdev, i, callbacks[i], names[i], vector);
if (IS_ERR(vqs[i])) {
err = PTR_ERR(vqs[i]);
goto error_find;
}
/* allocate per-vq irq if available and necessary */
if (vp_dev->per_vq_vectors && vector != VIRTIO_MSI_NO_VECTOR) {
snprintf(vp_dev->msix_names[vector], sizeof *vp_dev->msix_names,
"%s-%s", dev_name(&vp_dev->vdev.dev), names[i]);
err = request_irq(vp_dev->msix_entries[vector].vector,
vring_interrupt, 0,
vp_dev->msix_names[vector], vqs[i]);
if (err) {
vp_del_vq(vqs[i]);
goto error_find;
}
}
}
return 0;
error_find:
vp_del_vqs(vdev);
error_request:
return err;
}
/* the config->find_vqs() implementation */
static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
struct virtqueue *vqs[],
@ -504,29 +538,27 @@ static int vp_find_vqs(struct virtio_device *vdev, unsigned nvqs,
const char *names[])
{
int vectors = 0;
int i, err;
int i, uninitialized_var(err);
/* How many vectors would we like? */
for (i = 0; i < nvqs; ++i)
if (callbacks[i])
++vectors;
err = vp_request_vectors(vdev, vectors);
if (err)
goto error_request;
for (i = 0; i < nvqs; ++i) {
vqs[i] = vp_find_vq(vdev, i, callbacks[i], names[i]);
if (IS_ERR(vqs[i]))
goto error_find;
}
return 0;
error_find:
vp_del_vqs(vdev);
error_request:
return PTR_ERR(vqs[i]);
/* We want at most one vector per queue and one for config changes. */
err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
vectors + 1, true);
if (!err)
return 0;
/* Fallback to separate vectors for config and a shared for queues. */
err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
2, false);
if (!err)
return 0;
/* Finally fall back to regular interrupts. */
err = vp_try_to_find_vqs(vdev, nvqs, vqs, callbacks, names,
0, false);
return err;
}
static struct virtio_config_ops virtio_pci_config_ops = {

39
include/linux/lguest.h
View File

@ -1,5 +1,7 @@
/* Things the lguest guest needs to know. Note: like all lguest interfaces,
* this is subject to wild and random change between versions. */
/*
* Things the lguest guest needs to know. Note: like all lguest interfaces,
* this is subject to wild and random change between versions.
*/
#ifndef _LINUX_LGUEST_H
#define _LINUX_LGUEST_H
@ -11,32 +13,41 @@
#define LG_CLOCK_MIN_DELTA 100UL
#define LG_CLOCK_MAX_DELTA ULONG_MAX
/*G:031 The second method of communicating with the Host is to via "struct
/*G:031
* The second method of communicating with the Host is to via "struct
* lguest_data". Once the Guest's initialization hypercall tells the Host where
* this is, the Guest and Host both publish information in it. :*/
struct lguest_data
{
/* 512 == enabled (same as eflags in normal hardware). The Guest
* changes interrupts so often that a hypercall is too slow. */
* this is, the Guest and Host both publish information in it.
:*/
struct lguest_data {
/*
* 512 == enabled (same as eflags in normal hardware). The Guest
* changes interrupts so often that a hypercall is too slow.
*/
unsigned int irq_enabled;
/* Fine-grained interrupt disabling by the Guest */
DECLARE_BITMAP(blocked_interrupts, LGUEST_IRQS);
/* The Host writes the virtual address of the last page fault here,
/*
* The Host writes the virtual address of the last page fault here,
* which saves the Guest a hypercall. CR2 is the native register where
* this address would normally be found. */
* this address would normally be found.
*/
unsigned long cr2;
/* Wallclock time set by the Host. */
struct timespec time;
/* Interrupt pending set by the Host. The Guest should do a hypercall
* if it re-enables interrupts and sees this set (to X86_EFLAGS_IF). */
/*
* Interrupt pending set by the Host. The Guest should do a hypercall
* if it re-enables interrupts and sees this set (to X86_EFLAGS_IF).
*/
int irq_pending;
/* Async hypercall ring. Instead of directly making hypercalls, we can
/*
* Async hypercall ring. Instead of directly making hypercalls, we can
* place them in here for processing the next time the Host wants.
* This batching can be quite efficient. */
* This batching can be quite efficient.
*/
/* 0xFF == done (set by Host), 0 == pending (set by Guest). */
u8 hcall_status[LHCALL_RING_SIZE];

18
include/linux/lguest_launcher.h
View File

@ -29,8 +29,10 @@ struct lguest_device_desc {
__u8 type;
/* The number of virtqueues (first in config array) */
__u8 num_vq;
/* The number of bytes of feature bits. Multiply by 2: one for host
* features and one for Guest acknowledgements. */
/*
* The number of bytes of feature bits. Multiply by 2: one for host
* features and one for Guest acknowledgements.
*/
__u8 feature_len;
/* The number of bytes of the config array after virtqueues. */
__u8 config_len;
@ -39,8 +41,10 @@ struct lguest_device_desc {
__u8 config[0];
};
/*D:135 This is how we expect the device configuration field for a virtqueue
* to be laid out in config space. */
/*D:135
* This is how we expect the device configuration field for a virtqueue
* to be laid out in config space.
*/
struct lguest_vqconfig {
/* The number of entries in the virtio_ring */
__u16 num;
@ -61,7 +65,9 @@ enum lguest_req
LHREQ_EVENTFD, /* + address, fd. */
};
/* The alignment to use between consumer and producer parts of vring.
* x86 pagesize for historical reasons. */
/*
* The alignment to use between consumer and producer parts of vring.
* x86 pagesize for historical reasons.
*/
#define LGUEST_VRING_ALIGN 4096
#endif /* _LINUX_LGUEST_LAUNCHER */

6
include/linux/virtio_blk.h
View File

@ -20,8 +20,7 @@
#define VIRTIO_BLK_ID_BYTES (sizeof(__u16[256])) /* IDENTIFY DATA */
struct virtio_blk_config
{
struct virtio_blk_config {
/* The capacity (in 512-byte sectors). */
__u64 capacity;
/* The maximum segment size (if VIRTIO_BLK_F_SIZE_MAX) */
@ -50,8 +49,7 @@ struct virtio_blk_config
#define VIRTIO_BLK_T_BARRIER 0x80000000
/* This is the first element of the read scatter-gather list. */
struct virtio_blk_outhdr
{
struct virtio_blk_outhdr {
/* VIRTIO_BLK_T* */
__u32 type;
/* io priority. */

3
include/linux/virtio_config.h
View File

@ -79,8 +79,7 @@
* the dev->feature bits if it wants.
*/
typedef void vq_callback_t(struct virtqueue *);
struct virtio_config_ops
{
struct virtio_config_ops {
void (*get)(struct virtio_device *vdev, unsigned offset,
void *buf, unsigned len);
void (*set)(struct virtio_device *vdev, unsigned offset,

6
include/linux/virtio_net.h
View File

@ -31,8 +31,7 @@
#define VIRTIO_NET_S_LINK_UP 1 /* Link is up */
struct virtio_net_config
{
struct virtio_net_config {
/* The config defining mac address (if VIRTIO_NET_F_MAC) */
__u8 mac[6];
/* See VIRTIO_NET_F_STATUS and VIRTIO_NET_S_* above */
@ -41,8 +40,7 @@ struct virtio_net_config
/* This is the first element of the scatter-gather list. If you don't
* specify GSO or CSUM features, you can simply ignore the header. */
struct virtio_net_hdr
{
struct virtio_net_hdr {
#define VIRTIO_NET_HDR_F_NEEDS_CSUM 1 // Use csum_start, csum_offset
__u8 flags;
#define VIRTIO_NET_HDR_GSO_NONE 0 // Not a GSO frame

12
include/linux/virtio_ring.h
View File

@ -30,8 +30,7 @@
#define VIRTIO_RING_F_INDIRECT_DESC 28
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc
{
struct vring_desc {
/* Address (guest-physical). */
__u64 addr;
/* Length. */
@ -42,24 +41,21 @@ struct vring_desc
__u16 next;
};
struct vring_avail
{
struct vring_avail {
__u16 flags;
__u16 idx;
__u16 ring[];
};
/* u32 is used here for ids for padding reasons. */
struct vring_used_elem
{
struct vring_used_elem {
/* Index of start of used descriptor chain. */
__u32 id;
/* Total length of the descriptor chain which was used (written to) */
__u32 len;
};
struct vring_used
{
struct vring_used {
__u16 flags;
__u16 idx;
struct vring_used_elem ring[];