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KVM: x86: fix maintenance of guest/host xcr0 state 

Emulation of xcr0 writes zero guest_xcr0_loaded variable so that
subsequent VM-entry reloads CPU's xcr0 with guests xcr0 value.

However, this is incorrect because guest_xcr0_loaded variable is
read to decide whether to reload hosts xcr0.

In case the vcpu thread is scheduled out after the guest_xcr0_loaded = 0
assignment, and scheduler decides to preload FPU:

switch_to
{
  __switch_to
    __math_state_restore
      restore_fpu_checking
        fpu_restore_checking
          if (use_xsave())
              fpu_xrstor_checking
		xrstor64 with CPU's xcr0 == guests xcr0

Fix by properly restoring hosts xcr0 during emulation of xcr0 writes.

Analyzed-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
hifive-unleashed-5.1
Marcelo Tosatti 2013-04-15 23:30:13 -03:00 committed by Gleb Natapov
parent 5af43c24ca
commit 42bdf991f4
1 changed files with 20 additions and 20 deletions
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40
arch/x86/kvm/x86.c
View File

@ -555,6 +555,25 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
}
EXPORT_SYMBOL_GPL(kvm_lmsw);
static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu)
{
if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
!vcpu->guest_xcr0_loaded) {
/* kvm_set_xcr() also depends on this */
xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
vcpu->guest_xcr0_loaded = 1;
}
}
static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_xcr0_loaded) {
if (vcpu->arch.xcr0 != host_xcr0)
xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
vcpu->guest_xcr0_loaded = 0;
}
}
int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
{
u64 xcr0;
@ -571,8 +590,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
return 1;
if (xcr0 & ~host_xcr0)
return 1;
kvm_put_guest_xcr0(vcpu);
vcpu->arch.xcr0 = xcr0;
vcpu->guest_xcr0_loaded = 0;
return 0;
}
@ -5614,25 +5633,6 @@ static void inject_pending_event(struct kvm_vcpu *vcpu)
}
}
static void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu)
{
if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) &&
!vcpu->guest_xcr0_loaded) {
/* kvm_set_xcr() also depends on this */
xsetbv(XCR_XFEATURE_ENABLED_MASK, vcpu->arch.xcr0);
vcpu->guest_xcr0_loaded = 1;
}
}
static void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu)
{
if (vcpu->guest_xcr0_loaded) {
if (vcpu->arch.xcr0 != host_xcr0)
xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
vcpu->guest_xcr0_loaded = 0;
}
}
static void process_nmi(struct kvm_vcpu *vcpu)
{
unsigned limit = 2;