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KVM: Handle virtualization instruction #UD faults during reboot

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KVM turns off hardware virtualization extensions during reboot, in order
to disassociate the memory used by the virtualization extensions from the
processor, and in order to have the system in a consistent state.
Unfortunately virtual machines may still be running while this goes on,
and once virtualization extensions are turned off, any virtulization
instruction will #UD on execution.

Fix by adding an exception handler to virtualization instructions; if we get
an exception during reboot, we simply spin waiting for the reset to complete.
If it's a true exception, BUG() so we can have our stack trace.

Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Avi Kivity 2008-05-13 13:23:38 +03:00
parent 1b7fcd3263
commit 4ecac3fd6d
4 changed files with 64 additions and 20 deletions
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20
arch/x86/kvm/svm.c
View File

@ -27,6 +27,8 @@
#include <asm/desc.h>
#define __ex(x) __kvm_handle_fault_on_reboot(x)
MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");
@ -129,17 +131,17 @@ static inline void push_irq(struct kvm_vcpu *vcpu, u8 irq)
static inline void clgi(void)
{
asm volatile (SVM_CLGI);
asm volatile (__ex(SVM_CLGI));
}
static inline void stgi(void)
{
asm volatile (SVM_STGI);
asm volatile (__ex(SVM_STGI));
}
static inline void invlpga(unsigned long addr, u32 asid)
{
asm volatile (SVM_INVLPGA :: "a"(addr), "c"(asid));
asm volatile (__ex(SVM_INVLPGA) :: "a"(addr), "c"(asid));
}
static inline unsigned long kvm_read_cr2(void)
@ -1758,17 +1760,17 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
/* Enter guest mode */
"push %%rax \n\t"
"mov %c[vmcb](%[svm]), %%rax \n\t"
SVM_VMLOAD "\n\t"
SVM_VMRUN "\n\t"
SVM_VMSAVE "\n\t"
__ex(SVM_VMLOAD) "\n\t"
__ex(SVM_VMRUN) "\n\t"
__ex(SVM_VMSAVE) "\n\t"
"pop %%rax \n\t"
#else
/* Enter guest mode */
"push %%eax \n\t"
"mov %c[vmcb](%[svm]), %%eax \n\t"
SVM_VMLOAD "\n\t"
SVM_VMRUN "\n\t"
SVM_VMSAVE "\n\t"
__ex(SVM_VMLOAD) "\n\t"
__ex(SVM_VMRUN) "\n\t"
__ex(SVM_VMSAVE) "\n\t"
"pop %%eax \n\t"
#endif

25
arch/x86/kvm/vmx.c
View File

@ -30,6 +30,8 @@
#include <asm/io.h>
#include <asm/desc.h>
#define __ex(x) __kvm_handle_fault_on_reboot(x)
MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");
@ -278,7 +280,7 @@ static inline void __invvpid(int ext, u16 vpid, gva_t gva)
u64 gva;
} operand = { vpid, 0, gva };
asm volatile (ASM_VMX_INVVPID
asm volatile (__ex(ASM_VMX_INVVPID)
/* CF==1 or ZF==1 --> rc = -1 */
"; ja 1f ; ud2 ; 1:"
: : "a"(&operand), "c"(ext) : "cc", "memory");
@ -290,7 +292,7 @@ static inline void __invept(int ext, u64 eptp, gpa_t gpa)
u64 eptp, gpa;
} operand = {eptp, gpa};
asm volatile (ASM_VMX_INVEPT
asm volatile (__ex(ASM_VMX_INVEPT)
/* CF==1 or ZF==1 --> rc = -1 */
"; ja 1f ; ud2 ; 1:\n"
: : "a" (&operand), "c" (ext) : "cc", "memory");
@ -311,7 +313,7 @@ static void vmcs_clear(struct vmcs *vmcs)
u64 phys_addr = __pa(vmcs);
u8 error;
asm volatile (ASM_VMX_VMCLEAR_RAX "; setna %0"
asm volatile (__ex(ASM_VMX_VMCLEAR_RAX) "; setna %0"
: "=g"(error) : "a"(&phys_addr), "m"(phys_addr)
: "cc", "memory");
if (error)
@ -378,7 +380,7 @@ static unsigned long vmcs_readl(unsigned long field)
{
unsigned long value;
asm volatile (ASM_VMX_VMREAD_RDX_RAX
asm volatile (__ex(ASM_VMX_VMREAD_RDX_RAX)
: "=a"(value) : "d"(field) : "cc");
return value;
}
@ -413,7 +415,7 @@ static void vmcs_writel(unsigned long field, unsigned long value)
{
u8 error;
asm volatile (ASM_VMX_VMWRITE_RAX_RDX "; setna %0"
asm volatile (__ex(ASM_VMX_VMWRITE_RAX_RDX) "; setna %0"
: "=q"(error) : "a"(value), "d"(field) : "cc");
if (unlikely(error))
vmwrite_error(field, value);
@ -621,7 +623,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
u8 error;
per_cpu(current_vmcs, cpu) = vmx->vmcs;
asm volatile (ASM_VMX_VMPTRLD_RAX "; setna %0"
asm volatile (__ex(ASM_VMX_VMPTRLD_RAX) "; setna %0"
: "=g"(error) : "a"(&phys_addr), "m"(phys_addr)
: "cc");
if (error)
@ -1030,13 +1032,14 @@ static void hardware_enable(void *garbage)
MSR_IA32_FEATURE_CONTROL_LOCKED |
MSR_IA32_FEATURE_CONTROL_VMXON_ENABLED);
write_cr4(read_cr4() | X86_CR4_VMXE); /* FIXME: not cpu hotplug safe */
asm volatile (ASM_VMX_VMXON_RAX : : "a"(&phys_addr), "m"(phys_addr)
asm volatile (ASM_VMX_VMXON_RAX
: : "a"(&phys_addr), "m"(phys_addr)
: "memory", "cc");
}
static void hardware_disable(void *garbage)
{
asm volatile (ASM_VMX_VMXOFF : : : "cc");
asm volatile (__ex(ASM_VMX_VMXOFF) : : : "cc");
write_cr4(read_cr4() & ~X86_CR4_VMXE);
}
@ -2834,7 +2837,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
"push %%edx; push %%ebp;"
"push %%ecx \n\t"
#endif
ASM_VMX_VMWRITE_RSP_RDX "\n\t"
__ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
/* Check if vmlaunch of vmresume is needed */
"cmpl $0, %c[launched](%0) \n\t"
/* Load guest registers. Don't clobber flags. */
@ -2869,9 +2872,9 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
#endif
/* Enter guest mode */
"jne .Llaunched \n\t"
ASM_VMX_VMLAUNCH "\n\t"
__ex(ASM_VMX_VMLAUNCH) "\n\t"
"jmp .Lkvm_vmx_return \n\t"
".Llaunched: " ASM_VMX_VMRESUME "\n\t"
".Llaunched: " __ex(ASM_VMX_VMRESUME) "\n\t"
".Lkvm_vmx_return: "
/* Save guest registers, load host registers, keep flags */
#ifdef CONFIG_X86_64

24
include/asm-x86/kvm_host.h
View File

@ -692,4 +692,28 @@ enum {
trace_mark(kvm_trace_##name, "%u %p %u %u %u %u %u %u", KVM_TRC_##evt, \
vcpu, 0, 0, 0, 0, 0, 0)
#ifdef CONFIG_64BIT
#define KVM_EX_ENTRY ".quad"
#else
#define KVM_EX_ENTRY ".long"
#endif
/*
* Hardware virtualization extension instructions may fault if a
* reboot turns off virtualization while processes are running.
* Trap the fault and ignore the instruction if that happens.
*/
asmlinkage void kvm_handle_fault_on_reboot(void);
#define __kvm_handle_fault_on_reboot(insn) \
"666: " insn "\n\t" \
".pushsection .text.fixup, \"ax\" \n" \
"667: \n\t" \
"push $666b \n\t" \
"jmp kvm_handle_fault_on_reboot \n\t" \
".popsection \n\t" \
".pushsection __ex_table, \"a\" \n\t" \
KVM_EX_ENTRY " 666b, 667b \n\t" \
".popsection"
#endif

15
virt/kvm/kvm_main.c
View File

@ -65,6 +65,8 @@ struct dentry *kvm_debugfs_dir;
static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
unsigned long arg);
bool kvm_rebooting;
static inline int valid_vcpu(int n)
{
return likely(n >= 0 && n < KVM_MAX_VCPUS);
@ -1301,6 +1303,18 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
return NOTIFY_OK;
}
asmlinkage void kvm_handle_fault_on_reboot(void)
{
if (kvm_rebooting)
/* spin while reset goes on */
while (true)
;
/* Fault while not rebooting. We want the trace. */
BUG();
}
EXPORT_SYMBOL_GPL(kvm_handle_fault_on_reboot);
static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
void *v)
{
@ -1310,6 +1324,7 @@ static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
* in vmx root mode.
*/
printk(KERN_INFO "kvm: exiting hardware virtualization\n");
kvm_rebooting = true;
on_each_cpu(hardware_disable, NULL, 1);
}
return NOTIFY_OK;