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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: Fix in/out emulation
  lguest: Fix translation count about wikipedia's cpuid page
  lguest: Fix three simple typos in comments
  lguest: update comments
  lguest: Simplify device initialization.
  lguest: don't rewrite vmcall instructions
  lguest: remove remaining vmcall
  lguest: use a special 1:1 linear pagetable mode until first switch.
  lguest: Do not exit on non-fatal errors
This commit is contained in:
Linus Torvalds 2011-07-22 13:45:50 -07:00
parent 111ad119d1 996ba96a97
commit a7e1aabb28
13 changed files with 199 additions and 380 deletions
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47
Documentation/virtual/lguest/lguest.c
View File

@ -51,7 +51,7 @@
#include <asm/bootparam.h>
#include "../../../include/linux/lguest_launcher.h"
/*L:110
* We can ignore the 42 include files we need for this program, but I do want
* We can ignore the 43 include files we need for this program, but I do want
* to draw attention to the use of kernel-style types.
*
* As Linus said, "C is a Spartan language, and so should your naming be." I
@ -65,7 +65,6 @@ typedef uint16_t u16;
typedef uint8_t u8;
/*:*/
#define PAGE_PRESENT 0x7 /* Present, RW, Execute */
#define BRIDGE_PFX "bridge:"
#ifndef SIOCBRADDIF
#define SIOCBRADDIF 0x89a2 /* add interface to bridge */
@ -861,8 +860,10 @@ static void console_output(struct virtqueue *vq)
/* writev can return a partial write, so we loop here. */
while (!iov_empty(iov, out)) {
int len = writev(STDOUT_FILENO, iov, out);
if (len <= 0)
err(1, "Write to stdout gave %i", len);
if (len <= 0) {
warn("Write to stdout gave %i (%d)", len, errno);
break;
}
iov_consume(iov, out, len);
}
@ -898,7 +899,7 @@ static void net_output(struct virtqueue *vq)
* same format: what a coincidence!
*/
if (writev(net_info->tunfd, iov, out) < 0)
errx(1, "Write to tun failed?");
warnx("Write to tun failed (%d)?", errno);
/*
* Done with that one; wait_for_vq_desc() will send the interrupt if
@ -955,7 +956,7 @@ static void net_input(struct virtqueue *vq)
*/
len = readv(net_info->tunfd, iov, in);
if (len <= 0)
err(1, "Failed to read from tun.");
warn("Failed to read from tun (%d).", errno);
/*
* Mark that packet buffer as used, but don't interrupt here. We want
@ -1093,9 +1094,10 @@ static void update_device_status(struct device *dev)
warnx("Device %s configuration FAILED", dev->name);
if (dev->running)
reset_device(dev);
} else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) {
if (!dev->running)
start_device(dev);
} else {
if (dev->running)
err(1, "Device %s features finalized twice", dev->name);
start_device(dev);
}
}
@ -1120,25 +1122,11 @@ static void handle_output(unsigned long addr)
return;
}
/*
* Devices *can* be used before status is set to DRIVER_OK.
* The original plan was that they would never do this: they
* would always finish setting up their status bits before
* actually touching the virtqueues. In practice, we allowed
* them to, and they do (eg. the disk probes for partition
* tables as part of initialization).
*
* If we see this, we start the device: once it's running, we
* expect the device to catch all the notifications.
*/
/* Devices should not be used before features are finalized. */
for (vq = i->vq; vq; vq = vq->next) {
if (addr != vq->config.pfn*getpagesize())
continue;
if (i->running)
errx(1, "Notification on running %s", i->name);
/* This just calls create_thread() for each virtqueue */
start_device(i);
return;
errx(1, "Notification on %s before setup!", i->name);
}
}
@ -1370,7 +1358,7 @@ static void setup_console(void)
* --sharenet=<name> option which opens or creates a named pipe. This can be
* used to send packets to another guest in a 1:1 manner.
*
* More sopisticated is to use one of the tools developed for project like UML
* More sophisticated is to use one of the tools developed for project like UML
* to do networking.
*
* Faster is to do virtio bonding in kernel. Doing this 1:1 would be
@ -1380,7 +1368,7 @@ static void setup_console(void)
* multiple inter-guest channels behind one interface, although it would
* require some manner of hotplugging new virtio channels.
*
* Finally, we could implement a virtio network switch in the kernel.
* Finally, we could use a virtio network switch in the kernel, ie. vhost.
:*/
static u32 str2ip(const char *ipaddr)
@ -2017,10 +2005,7 @@ int main(int argc, char *argv[])
/* Tell the entry path not to try to reload segment registers. */
boot->hdr.loadflags |= KEEP_SEGMENTS;
/*
* We tell the kernel to initialize the Guest: this returns the open
* /dev/lguest file descriptor.
*/
/* We tell the kernel to initialize the Guest. */
tell_kernel(start);
/* Ensure that we terminate if a device-servicing child dies. */

1
arch/x86/include/asm/lguest_hcall.h
View File

@ -61,6 +61,7 @@ hcall(unsigned long call,
: "memory");
return call;
}
/*:*/
/* Can't use our min() macro here: needs to be a constant */
#define LGUEST_IRQS (NR_IRQS < 32 ? NR_IRQS: 32)

1
arch/x86/kernel/asm-offsets_32.c
View File

@ -63,7 +63,6 @@ void foo(void)
BLANK();
OFFSET(LGUEST_DATA_irq_enabled, lguest_data, irq_enabled);
OFFSET(LGUEST_DATA_irq_pending, lguest_data, irq_pending);
OFFSET(LGUEST_DATA_pgdir, lguest_data, pgdir);
BLANK();
OFFSET(LGUEST_PAGES_host_gdt_desc, lguest_pages, state.host_gdt_desc);

36
arch/x86/lguest/boot.c
View File

@ -71,7 +71,8 @@
#include <asm/stackprotector.h>
#include <asm/reboot.h> /* for struct machine_ops */
/*G:010 Welcome to the Guest!
/*G:010
* Welcome to the Guest!
*
* The Guest in our tale is a simple creature: identical to the Host but
* behaving in simplified but equivalent ways. In particular, the Guest is the
@ -190,15 +191,23 @@ static void lazy_hcall4(unsigned long call,
#endif
/*G:036
* When lazy mode is turned off reset the per-cpu lazy mode variable and then
* issue the do-nothing hypercall to flush any stored calls.
:*/
* When lazy mode is turned off, we issue the do-nothing hypercall to
* flush any stored calls, and call the generic helper to reset the
* per-cpu lazy mode variable.
*/
static void lguest_leave_lazy_mmu_mode(void)
{
hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0, 0);
paravirt_leave_lazy_mmu();
}
/*
* We also catch the end of context switch; we enter lazy mode for much of
* that too, so again we need to flush here.
*
* (Technically, this is lazy CPU mode, and normally we're in lazy MMU
* mode, but unlike Xen, lguest doesn't care about the difference).
*/
static void lguest_end_context_switch(struct task_struct *next)
{
hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0, 0);
@ -391,7 +400,7 @@ static void lguest_load_tr_desc(void)
* giant ball of hair. Its entry in the current Intel manual runs to 28 pages.
*
* This instruction even it has its own Wikipedia entry. The Wikipedia entry
* has been translated into 5 languages. I am not making this up!
* has been translated into 6 languages. I am not making this up!
*
* We could get funky here and identify ourselves as "GenuineLguest", but
* instead we just use the real "cpuid" instruction. Then I pretty much turned
@ -458,7 +467,7 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
/*
* PAE systems can mark pages as non-executable. Linux calls this the
* NX bit. Intel calls it XD (eXecute Disable), AMD EVP (Enhanced
* Virus Protection). We just switch turn if off here, since we don't
* Virus Protection). We just switch it off here, since we don't
* support it.
*/
case 0x80000001:
@ -520,17 +529,16 @@ static unsigned long lguest_read_cr2(void)
/* See lguest_set_pte() below. */
static bool cr3_changed = false;
static unsigned long current_cr3;
/*
* cr3 is the current toplevel pagetable page: the principle is the same as
* cr0. Keep a local copy, and tell the Host when it changes. The only
* difference is that our local copy is in lguest_data because the Host needs
* to set it upon our initial hypercall.
* cr0. Keep a local copy, and tell the Host when it changes.
*/
static void lguest_write_cr3(unsigned long cr3)
{
lguest_data.pgdir = cr3;
lazy_hcall1(LHCALL_NEW_PGTABLE, cr3);
current_cr3 = cr3;
/* These two page tables are simple, linear, and used during boot */
if (cr3 != __pa(swapper_pg_dir) && cr3 != __pa(initial_page_table))
@ -539,7 +547,7 @@ static void lguest_write_cr3(unsigned long cr3)
static unsigned long lguest_read_cr3(void)
{
return lguest_data.pgdir;
return current_cr3;
}
/* cr4 is used to enable and disable PGE, but we don't care. */
@ -641,7 +649,7 @@ static void lguest_write_cr4(unsigned long val)
/*
* The Guest calls this after it has set a second-level entry (pte), ie. to map
* a page into a process' address space. Wetell the Host the toplevel and
* a page into a process' address space. We tell the Host the toplevel and
* address this corresponds to. The Guest uses one pagetable per process, so
* we need to tell the Host which one we're changing (mm->pgd).
*/
@ -758,7 +766,7 @@ static void lguest_pmd_clear(pmd_t *pmdp)
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
lazy_hcall3(LHCALL_SET_PTE, current_cr3, addr, 0);
}
/*
@ -1140,7 +1148,7 @@ static struct notifier_block paniced = {
static __init char *lguest_memory_setup(void)
{
/*
*The Linux bootloader header contains an "e820" memory map: the
* The Linux bootloader header contains an "e820" memory map: the
* Launcher populated the first entry with our memory limit.
*/
e820_add_region(boot_params.e820_map[0].addr,

35
arch/x86/lguest/i386_head.S
View File

@ -6,18 +6,22 @@
#include <asm/processor-flags.h>
/*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).
* Our story starts with the bzImage: booting starts at startup_32 in
* arch/x86/boot/compressed/head_32.S. This merely uncompresses the real
* kernel in place and then jumps into it: startup_32 in
* arch/x86/kernel/head_32.S. Both routines expects a boot header in the %esi
* register, which is created by the bootloader (the Launcher in our case).
*
* The startup_32 function does very little: it clears the uninitialized global
* C variables which we expect to be zero (ie. BSS) and then copies the boot
* header and kernel command line somewhere safe. Finally it checks the
* 'hardware_subarch' field. This was introduced in 2.6.24 for lguest and Xen:
* if it's set to '1' (lguest's assigned number), then it calls us here.
* header and kernel command line somewhere safe, and populates some initial
* page tables. Finally it checks the 'hardware_subarch' field. This was
* introduced in 2.6.24 for lguest and Xen: if it's set to '1' (lguest's
* assigned number), then it calls us here.
*
* WARNING: be very careful here! We're running at addresses equal to physical
* addesses (around 0), not above PAGE_OFFSET as most code expectes
* addresses (around 0), not above PAGE_OFFSET as most code expects
* (eg. 0xC0000000). Jumps are relative, so they're OK, but we can't touch any
* data without remembering to subtract __PAGE_OFFSET!
*
@ -27,13 +31,18 @@
.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 where
* our lguest_data struct is.
*/
movl $LHCALL_LGUEST_INIT, %eax
movl $lguest_data - __PAGE_OFFSET, %ebx
int $LGUEST_TRAP_ENTRY
/* Now turn our pagetables on; setup by arch/x86/kernel/head_32.S. */
movl $LHCALL_NEW_PGTABLE, %eax
movl $(initial_page_table - __PAGE_OFFSET), %ebx
int $LGUEST_TRAP_ENTRY
/* Set up the initial stack so we can run C code. */
movl $(init_thread_union+THREAD_SIZE),%esp
@ -96,12 +105,8 @@ send_interrupts:
*/
pushl %eax
movl $LHCALL_SEND_INTERRUPTS, %eax
/*
* 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.
*/
.byte 0x0f,0x01,0xc1 /* KVM_HYPERCALL */
/* This is the actual hypercall trap. */
int $LGUEST_TRAP_ENTRY
/* Put eax back the way we found it. */
popl %eax
ret

2
drivers/lguest/core.c
View File

@ -117,7 +117,7 @@ static __init int map_switcher(void)
/*
* Now the Switcher is mapped at the right address, we can't fail!
* Copy in the compiled-in Switcher code (from <arch>_switcher.S).
* Copy in the compiled-in Switcher code (from x86/switcher_32.S).
*/
memcpy(switcher_vma->addr, start_switcher_text,
end_switcher_text - start_switcher_text);

10
drivers/lguest/interrupts_and_traps.c
View File

@ -375,11 +375,9 @@ static bool direct_trap(unsigned int num)
/*
* 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.
* device not available (TS handling) and of course, the hypercall trap.
*/
return num != 14 && num != 13 && num != 7 &&
num != 6 && num != LGUEST_TRAP_ENTRY;
return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY;
}
/*:*/
@ -429,8 +427,8 @@ void pin_stack_pages(struct lg_cpu *cpu)
/*
* 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
* a different kernel stack, so we can change the guest TSS to use that
* stack. The TSS entries expect a virtual address, so unlike most addresses
* the Guest gives us, the "esp" (stack pointer) value here is virtual, not
* physical.
*

2
drivers/lguest/lg.h
View File

@ -59,6 +59,8 @@ struct lg_cpu {
struct lguest_pages *last_pages;
/* Initialization mode: linear map everything. */
bool linear_pages;
int cpu_pgd; /* Which pgd this cpu is currently using */
/* If a hypercall was asked for, this points to the arguments. */

37
drivers/lguest/lguest_device.c
View File

@ -108,6 +108,17 @@ static u32 lg_get_features(struct virtio_device *vdev)
return features;
}
/*
* To notify on reset or feature finalization, we (ab)use the NOTIFY
* hypercall, with the descriptor address of the device.
*/
static void status_notify(struct virtio_device *vdev)
{
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
hcall(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset, 0, 0, 0);
}
/*
* 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
@ -135,6 +146,9 @@ static void lg_finalize_features(struct virtio_device *vdev)
if (test_bit(i, vdev->features))
out_features[i / 8] |= (1 << (i % 8));
}
/* Tell Host we've finished with this device's feature negotiation */
status_notify(vdev);
}
/* Once they've found a field, getting a copy of it is easy. */
@ -168,28 +182,21 @@ 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".
*/
static void set_status(struct virtio_device *vdev, u8 status)
{
unsigned long offset = (void *)to_lgdev(vdev)->desc - lguest_devices;
/* We set the status. */
to_lgdev(vdev)->desc->status = status;
hcall(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset, 0, 0, 0);
}
static void lg_set_status(struct virtio_device *vdev, u8 status)
{
BUG_ON(!status);
set_status(vdev, status);
to_lgdev(vdev)->desc->status = status;
/* Tell Host immediately if we failed. */
if (status & VIRTIO_CONFIG_S_FAILED)
status_notify(vdev);
}
static void lg_reset(struct virtio_device *vdev)
{
set_status(vdev, 0);
/* 0 status means "reset" */
to_lgdev(vdev)->desc->status = 0;
status_notify(vdev);
}
/*

17
drivers/lguest/lguest_user.c
View File

@ -1,8 +1,10 @@
/*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 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.
/*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 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. There is
* also a way for the Launcher to attach eventfds to particular NOTIFY
* values instead of returning from the read() call.
:*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
@ -357,8 +359,8 @@ static int initialize(struct file *file, const unsigned long __user *input)
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. This allocates
* memory, so can fail.
*/
err = init_guest_pagetable(lg);
if (err)
@ -516,6 +518,7 @@ static const struct file_operations lguest_fops = {
.read = read,
.llseek = default_llseek,
};
/*:*/
/*
* This is a textbook example of a "misc" character device. Populate a "struct

282
drivers/lguest/page_tables.c
View File

@ -17,7 +17,6 @@
#include <linux/percpu.h>
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
#include <asm/bootparam.h>
#include "lg.h"
/*M:008
@ -156,7 +155,7 @@ static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
}
/*
* These functions are just like the above two, except they access the Guest
* These functions are just like the above, except they access the Guest
* page tables. Hence they return a Guest address.
*/
static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
@ -196,7 +195,7 @@ static unsigned long gpte_addr(struct lg_cpu *cpu,
#endif
/*:*/
/*M:014
/*M:007
* get_pfn is slow: we could probably try to grab batches of pages here as
* an optimization (ie. pre-faulting).
:*/
@ -325,10 +324,15 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
#endif
/* First step: get the top-level Guest page table entry. */
gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
/* Toplevel not present? We can't map it in. */
if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
return false;
if (unlikely(cpu->linear_pages)) {
/* Faking up a linear mapping. */
gpgd = __pgd(CHECK_GPGD_MASK);
} else {
gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
/* Toplevel not present? We can't map it in. */
if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
return false;
}
/* Now look at the matching shadow entry. */
spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
@ -353,10 +357,15 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
}
#ifdef CONFIG_X86_PAE
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
/* Middle level not present? We can't map it in. */
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
return false;
if (unlikely(cpu->linear_pages)) {
/* Faking up a linear mapping. */
gpmd = __pmd(_PAGE_TABLE);
} else {
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
/* Middle level not present? We can't map it in. */
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
return false;
}
/* Now look at the matching shadow entry. */
spmd = spmd_addr(cpu, *spgd, vaddr);
@ -397,8 +406,13 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
gpte_ptr = gpte_addr(cpu, gpgd, vaddr);
#endif
/* Read the actual PTE value. */
gpte = lgread(cpu, gpte_ptr, pte_t);
if (unlikely(cpu->linear_pages)) {
/* Linear? Make up a PTE which points to same page. */
gpte = __pte((vaddr & PAGE_MASK) | _PAGE_RW | _PAGE_PRESENT);
} else {
/* Read the actual PTE value. */
gpte = lgread(cpu, gpte_ptr, pte_t);
}
/* If this page isn't in the Guest page tables, we can't page it in. */
if (!(pte_flags(gpte) & _PAGE_PRESENT))
@ -454,7 +468,8 @@ bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
* Finally, we write the Guest PTE entry back: we've set the
* _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags.
*/
lgwrite(cpu, gpte_ptr, pte_t, gpte);
if (likely(!cpu->linear_pages))
lgwrite(cpu, gpte_ptr, pte_t, gpte);
/*
* The fault is fixed, the page table is populated, the mapping
@ -612,6 +627,11 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
#ifdef CONFIG_X86_PAE
pmd_t gpmd;
#endif
/* Still not set up? Just map 1:1. */
if (unlikely(cpu->linear_pages))
return vaddr;
/* First step: get the top-level Guest page table entry. */
gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
/* Toplevel not present? We can't map it in. */
@ -708,32 +728,6 @@ static unsigned int new_pgdir(struct lg_cpu *cpu,
return next;
}
/*H:430
* (iv) Switching page tables
*
* Now we've seen all the page table setting and manipulation, let's see
* what happens when the Guest changes page tables (ie. changes the top-level
* pgdir). This occurs on almost every context switch.
*/
void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
{
int newpgdir, repin = 0;
/* Look to see if we have this one already. */
newpgdir = find_pgdir(cpu->lg, pgtable);
/*
* If not, we allocate or mug an existing one: if it's a fresh one,
* repin gets set to 1.
*/
if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs))
newpgdir = new_pgdir(cpu, pgtable, &repin);
/* Change the current pgd index to the new one. */
cpu->cpu_pgd = newpgdir;
/* If it was completely blank, we map in the Guest kernel stack */
if (repin)
pin_stack_pages(cpu);
}
/*H:470
* Finally, a routine which throws away everything: all PGD entries in all
* the shadow page tables, including the Guest's kernel mappings. This is used
@ -780,6 +774,44 @@ void guest_pagetable_clear_all(struct lg_cpu *cpu)
/* We need the Guest kernel stack mapped again. */
pin_stack_pages(cpu);
}
/*H:430
* (iv) Switching page tables
*
* Now we've seen all the page table setting and manipulation, let's see
* what happens when the Guest changes page tables (ie. changes the top-level
* pgdir). This occurs on almost every context switch.
*/
void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
{
int newpgdir, repin = 0;
/*
* The very first time they call this, we're actually running without
* any page tables; we've been making it up. Throw them away now.
*/
if (unlikely(cpu->linear_pages)) {
release_all_pagetables(cpu->lg);
cpu->linear_pages = false;
/* Force allocation of a new pgdir. */
newpgdir = ARRAY_SIZE(cpu->lg->pgdirs);
} else {
/* Look to see if we have this one already. */
newpgdir = find_pgdir(cpu->lg, pgtable);
}
/*
* If not, we allocate or mug an existing one: if it's a fresh one,
* repin gets set to 1.
*/
if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs))
newpgdir = new_pgdir(cpu, pgtable, &repin);
/* Change the current pgd index to the new one. */
cpu->cpu_pgd = newpgdir;
/* If it was completely blank, we map in the Guest kernel stack */
if (repin)
pin_stack_pages(cpu);
}
/*:*/
/*M:009
@ -919,168 +951,26 @@ void guest_set_pmd(struct lguest *lg, unsigned long pmdp, u32 idx)
}
#endif
/*H:505
* To get through boot, we construct simple identity page mappings (which
* set virtual == physical) and linear mappings which will get the Guest far
* enough into the boot to create its own. The linear mapping means we
* simplify the Guest boot, but it makes assumptions about their PAGE_OFFSET,
* as you'll see.
*
* We lay them out of the way, just below the initrd (which is why we need to
* know its size here).
*/
static unsigned long setup_pagetables(struct lguest *lg,
unsigned long mem,
unsigned long initrd_size)
{
pgd_t __user *pgdir;
pte_t __user *linear;
unsigned long mem_base = (unsigned long)lg->mem_base;
unsigned int mapped_pages, i, linear_pages;
#ifdef CONFIG_X86_PAE
pmd_t __user *pmds;
unsigned int j;
pgd_t pgd;
pmd_t pmd;
#else
unsigned int phys_linear;
#endif
/*
* We have mapped_pages frames to map, so we need linear_pages page
* tables to map them.
*/
mapped_pages = mem / PAGE_SIZE;
linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE;
/* We put the toplevel page directory page at the top of memory. */
pgdir = (pgd_t *)(mem + mem_base - initrd_size - PAGE_SIZE);
/* Now we use the next linear_pages pages as pte pages */
linear = (void *)pgdir - linear_pages * PAGE_SIZE;
#ifdef CONFIG_X86_PAE
/*
* And the single mid page goes below that. We only use one, but
* that's enough to map 1G, which definitely gets us through boot.
*/
pmds = (void *)linear - PAGE_SIZE;
#endif
/*
* Linear mapping is easy: put every page's address into the
* mapping in order.
*/
for (i = 0; i < mapped_pages; i++) {
pte_t pte;
pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER));
if (copy_to_user(&linear[i], &pte, sizeof(pte)) != 0)
return -EFAULT;
}
#ifdef CONFIG_X86_PAE
/*
* Make the Guest PMD entries point to the corresponding place in the
* linear mapping (up to one page worth of PMD).
*/
for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD;
i += PTRS_PER_PTE, j++) {
pmd = pfn_pmd(((unsigned long)&linear[i] - mem_base)/PAGE_SIZE,
__pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER));
if (copy_to_user(&pmds[j], &pmd, sizeof(pmd)) != 0)
return -EFAULT;
}
/* One PGD entry, pointing to that PMD page. */
pgd = __pgd(((unsigned long)pmds - mem_base) | _PAGE_PRESENT);
/* Copy it in as the first PGD entry (ie. addresses 0-1G). */
if (copy_to_user(&pgdir[0], &pgd, sizeof(pgd)) != 0)
return -EFAULT;
/*
* And the other PGD entry to make the linear mapping at PAGE_OFFSET
*/
if (copy_to_user(&pgdir[KERNEL_PGD_BOUNDARY], &pgd, sizeof(pgd)))
return -EFAULT;
#else
/*
* The top level points to the linear page table pages above.
* We setup the identity and linear mappings here.
*/
phys_linear = (unsigned long)linear - mem_base;
for (i = 0; i < mapped_pages; i += PTRS_PER_PTE) {
pgd_t pgd;
/*
* Create a PGD entry which points to the right part of the
* linear PTE pages.
*/
pgd = __pgd((phys_linear + i * sizeof(pte_t)) |
(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER));
/*
* Copy it into the PGD page at 0 and PAGE_OFFSET.
*/
if (copy_to_user(&pgdir[i / PTRS_PER_PTE], &pgd, sizeof(pgd))
|| copy_to_user(&pgdir[pgd_index(PAGE_OFFSET)
+ i / PTRS_PER_PTE],
&pgd, sizeof(pgd)))
return -EFAULT;
}
#endif
/*
* We return the top level (guest-physical) address: we remember where
* this is to write it into lguest_data when the Guest initializes.
*/
return (unsigned long)pgdir - mem_base;
}
/*H:500
* (vii) Setting up the page tables initially.
*
* When a Guest is first created, the Launcher tells us where the toplevel of
* its first page table is. We set some things up here:
* When a Guest is first created, set initialize a shadow page table which
* we will populate on future faults. The Guest doesn't have any actual
* pagetables yet, so we set linear_pages to tell demand_page() to fake it
* for the moment.
*/
int init_guest_pagetable(struct lguest *lg)
{
u64 mem;
u32 initrd_size;
struct boot_params __user *boot = (struct boot_params *)lg->mem_base;
#ifdef CONFIG_X86_PAE
pgd_t *pgd;
pmd_t *pmd_table;
#endif
/*
* Get the Guest memory size and the ramdisk size from the boot header
* located at lg->mem_base (Guest address 0).
*/
if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem))
|| get_user(initrd_size, &boot->hdr.ramdisk_size))
return -EFAULT;
struct lg_cpu *cpu = &lg->cpus[0];
int allocated = 0;
/*
* We start on the first shadow page table, and give it a blank PGD
* page.
*/
lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size);
if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir))
return lg->pgdirs[0].gpgdir;
lg->pgdirs[0].pgdir = (pgd_t *)get_zeroed_page(GFP_KERNEL);
if (!lg->pgdirs[0].pgdir)
/* lg (and lg->cpus[]) starts zeroed: this allocates a new pgdir */
cpu->cpu_pgd = new_pgdir(cpu, 0, &allocated);
if (!allocated)
return -ENOMEM;
#ifdef CONFIG_X86_PAE
/* For PAE, we also create the initial mid-level. */
pgd = lg->pgdirs[0].pgdir;
pmd_table = (pmd_t *) get_zeroed_page(GFP_KERNEL);
if (!pmd_table)
return -ENOMEM;
set_pgd(pgd + SWITCHER_PGD_INDEX,
__pgd(__pa(pmd_table) | _PAGE_PRESENT));
#endif
/* This is the current page table. */
lg->cpus[0].cpu_pgd = 0;
/* We start with a linear mapping until the initialize. */
cpu->linear_pages = true;
return 0;
}
@ -1095,10 +985,10 @@ void page_table_guest_data_init(struct lg_cpu *cpu)
* of virtual addresses used by the Switcher.
*/
|| put_user(RESERVE_MEM * 1024 * 1024,
&cpu->lg->lguest_data->reserve_mem)
|| put_user(cpu->lg->pgdirs[0].gpgdir,
&cpu->lg->lguest_data->pgdir))
&cpu->lg->lguest_data->reserve_mem)) {
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
return;
}
/*
* In flush_user_mappings() we loop from 0 to

107
drivers/lguest/x86/core.c
View File

@ -269,10 +269,10 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
static int emulate_insn(struct lg_cpu *cpu)
{
u8 insn;
unsigned int insnlen = 0, in = 0, shift = 0;
unsigned int insnlen = 0, in = 0, small_operand = 0;
/*
* The eip contains the *virtual* address of the Guest's instruction:
* guest_pa just subtracts the Guest's page_offset.
* walk the Guest's page tables to find the "physical" address.
*/
unsigned long physaddr = guest_pa(cpu, cpu->regs->eip);
@ -300,11 +300,10 @@ static int emulate_insn(struct lg_cpu *cpu)
}
/*
* 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 a 16, not 32 bit in/out.
*/
if (insn == 0x66) {
shift = 16;
small_operand = 1;
/* The instruction is 1 byte so far, read the next byte. */
insnlen = 1;
insn = lgread(cpu, physaddr + insnlen, u8);
@ -340,11 +339,14 @@ static int emulate_insn(struct lg_cpu *cpu)
* traditionally means "there's nothing there".
*/
if (in) {
/* Lower bit tells is whether it's a 16 or 32 bit access */
if (insn & 0x1)
cpu->regs->eax = 0xFFFFFFFF;
else
cpu->regs->eax |= (0xFFFF << shift);
/* Lower bit tells means it's a 32/16 bit access */
if (insn & 0x1) {
if (small_operand)
cpu->regs->eax |= 0xFFFF;
else
cpu->regs->eax = 0xFFFFFFFF;
} else
cpu->regs->eax |= 0xFF;
}
/* Finally, we've "done" the instruction, so move past it. */
cpu->regs->eip += insnlen;
@ -352,69 +354,6 @@ static int emulate_insn(struct lg_cpu *cpu)
return 1;
}
/*
* 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.
*
* KVM_HYPERCALL is actually a "vmcall" instruction, which generates an invalid
* opcode fault (fault 6) on non-VT cpus, so the easiest solution seemed to be
* an *emulation approach*: if the fault was really produced by an hypercall
* (is_hypercall() does exactly this check), we can just call the corresponding
* hypercall host implementation function.
*
* But these invalid opcode faults are notably slower than software interrupts.
* So we implemented the *patching (or rewriting) approach*: every time we hit
* the KVM_HYPERCALL opcode in Guest code, we patch it to the old "int 0x1f"
* opcode, so next time the Guest calls this hypercall it will use the
* faster trap mechanism.
*
* Matias even benchmarked it to convince you: this shows the average cycle
* cost of a hypercall. For each alternative solution mentioned above we've
* made 5 runs of the benchmark:
*
* 1) direct software interrupt: 2915, 2789, 2764, 2721, 2898
* 2) emulation technique: 3410, 3681, 3466, 3392, 3780
* 3) patching (rewrite) technique: 2977, 2975, 2891, 2637, 2884
*
* One two-line function is worth a 20% hypercall speed boost!
*/
static void rewrite_hypercall(struct lg_cpu *cpu)
{
/*
* 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).
*/
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
* (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.
*/
guest_pagetable_clear_all(cpu);
}
static bool is_hypercall(struct lg_cpu *cpu)
{
u8 insn[3];
/*
* This must be the Guest kernel trying to do something.
* The bottom two bits of the CS segment register are the privilege
* level.
*/
if ((cpu->regs->cs & 3) != GUEST_PL)
return false;
/* Is it a vmcall? */
__lgread(cpu, insn, guest_pa(cpu, cpu->regs->eip), sizeof(insn));
return insn[0] == 0x0f && insn[1] == 0x01 && insn[2] == 0xc1;
}
/*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
void lguest_arch_handle_trap(struct lg_cpu *cpu)
{
@ -429,20 +368,6 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
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):
*/
case 6:
/*
* 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. */
/*
@ -486,7 +411,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
* 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;
@ -536,7 +461,7 @@ 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 x86/switcher_32.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.
*
@ -664,7 +589,7 @@ void __init lguest_arch_host_init(void)
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_PGE);
}
put_online_cpus();
};
}
/*:*/
void __exit lguest_arch_host_fini(void)
@ -747,8 +672,6 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
/*:*/
/*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.
*/

2
include/linux/lguest.h
View File

@ -59,8 +59,6 @@ struct lguest_data {
unsigned long reserve_mem;
/* KHz for the TSC clock. */
u32 tsc_khz;
/* Page where the top-level pagetable is */
unsigned long pgdir;
/* Fields initialized by the Guest at boot: */
/* Instruction range to suppress interrupts even if enabled */