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xen/pvh: Secondary VCPU bringup (non-bootup CPUs) 

The VCPU bringup protocol follows the PV with certain twists.
From xen/include/public/arch-x86/xen.h:

Also note that when calling DOMCTL_setvcpucontext and VCPU_initialise
for HVM and PVH guests, not all information in this structure is updated:

 - For HVM guests, the structures read include: fpu_ctxt (if
 VGCT_I387_VALID is set), flags, user_regs, debugreg[*]

 - PVH guests are the same as HVM guests, but additionally use ctrlreg[3] to
 set cr3. All other fields not used should be set to 0.

This is what we do. We piggyback on the 'xen_setup_gdt' - but modify
a bit - we need to call 'load_percpu_segment' so that 'switch_to_new_gdt'
can load per-cpu data-structures. It has no effect on the VCPU0.

We also piggyback on the %rdi register to pass in the CPU number - so
that when we bootup a new CPU, the cpu_bringup_and_idle will have
passed as the first parameter the CPU number (via %rdi for 64-bit).

Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Mukesh Rathor 2013-12-13 11:48:08 -05:00 committed by Konrad Rzeszutek Wilk
parent 8d656bbe43
commit 5840c84b16
3 changed files with 42 additions and 19 deletions
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11
arch/x86/xen/enlighten.c
View File

@ -1409,14 +1409,19 @@ static void __init xen_boot_params_init_edd(void)
* Set up the GDT and segment registers for -fstack-protector. Until
* we do this, we have to be careful not to call any stack-protected
* function, which is most of the kernel.
*
* Note, that it is __ref because the only caller of this after init
* is PVH which is not going to use xen_load_gdt_boot or other
* __init functions.
*/
static void __init xen_setup_gdt(void)
void __ref xen_setup_gdt(int cpu)
{
if (xen_feature(XENFEAT_auto_translated_physmap)) {
#ifdef CONFIG_X86_64
unsigned long dummy;
switch_to_new_gdt(0); /* GDT and GS set */
load_percpu_segment(cpu); /* We need to access per-cpu area */
switch_to_new_gdt(cpu); /* GDT and GS set */
/* We are switching of the Xen provided GDT to our HVM mode
* GDT. The new GDT has __KERNEL_CS with CS.L = 1
@ -1529,7 +1534,7 @@ asmlinkage void __init xen_start_kernel(void)
* Set up kernel GDT and segment registers, mainly so that
* -fstack-protector code can be executed.
*/
xen_setup_gdt();
xen_setup_gdt(0);
xen_init_irq_ops();
xen_init_cpuid_mask();

49
arch/x86/xen/smp.c
View File

@ -73,9 +73,11 @@ static void cpu_bringup(void)
touch_softlockup_watchdog();
preempt_disable();
xen_enable_sysenter();
xen_enable_syscall();
/* PVH runs in ring 0 and allows us to do native syscalls. Yay! */
if (!xen_feature(XENFEAT_supervisor_mode_kernel)) {
xen_enable_sysenter();
xen_enable_syscall();
}
cpu = smp_processor_id();
smp_store_cpu_info(cpu);
cpu_data(cpu).x86_max_cores = 1;
@ -97,8 +99,14 @@ static void cpu_bringup(void)
wmb(); /* make sure everything is out */
}
static void cpu_bringup_and_idle(void)
/* Note: cpu parameter is only relevant for PVH */
static void cpu_bringup_and_idle(int cpu)
{
#ifdef CONFIG_X86_64
if (xen_feature(XENFEAT_auto_translated_physmap) &&
xen_feature(XENFEAT_supervisor_mode_kernel))
xen_setup_gdt(cpu);
#endif
cpu_bringup();
cpu_startup_entry(CPUHP_ONLINE);
}
@ -274,9 +282,10 @@ static void __init xen_smp_prepare_boot_cpu(void)
native_smp_prepare_boot_cpu();
if (xen_pv_domain()) {
/* We've switched to the "real" per-cpu gdt, so make sure the
old memory can be recycled */
make_lowmem_page_readwrite(xen_initial_gdt);
if (!xen_feature(XENFEAT_writable_page_tables))
/* We've switched to the "real" per-cpu gdt, so make
* sure the old memory can be recycled. */
make_lowmem_page_readwrite(xen_initial_gdt);
#ifdef CONFIG_X86_32
/*
@ -360,22 +369,21 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
gdt = get_cpu_gdt_table(cpu);
ctxt->flags = VGCF_IN_KERNEL;
ctxt->user_regs.ss = __KERNEL_DS;
#ifdef CONFIG_X86_32
/* Note: PVH is not yet supported on x86_32. */
ctxt->user_regs.fs = __KERNEL_PERCPU;
ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
#else
ctxt->gs_base_kernel = per_cpu_offset(cpu);
#endif
ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
{
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
ctxt->flags = VGCF_IN_KERNEL;
ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
ctxt->user_regs.ds = __USER_DS;
ctxt->user_regs.es = __USER_DS;
ctxt->user_regs.ss = __KERNEL_DS;
xen_copy_trap_info(ctxt->trap_ctxt);
@ -396,18 +404,27 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
#ifdef CONFIG_X86_32
ctxt->event_callback_cs = __KERNEL_CS;
ctxt->failsafe_callback_cs = __KERNEL_CS;
#else
ctxt->gs_base_kernel = per_cpu_offset(cpu);
#endif
ctxt->event_callback_eip =
(unsigned long)xen_hypervisor_callback;
ctxt->failsafe_callback_eip =
(unsigned long)xen_failsafe_callback;
ctxt->user_regs.cs = __KERNEL_CS;
per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
#ifdef CONFIG_X86_32
}
ctxt->user_regs.cs = __KERNEL_CS;
#else
} else
/* N.B. The user_regs.eip (cpu_bringup_and_idle) is called with
* %rdi having the cpu number - which means are passing in
* as the first parameter the cpu. Subtle!
*/
ctxt->user_regs.rdi = cpu;
#endif
ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
BUG();

1
arch/x86/xen/xen-ops.h
View File

@ -123,4 +123,5 @@ __visible void xen_adjust_exception_frame(void);
extern int xen_panic_handler_init(void);
void xen_setup_gdt(int cpu);
#endif /* XEN_OPS_H */