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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2013-04-15 23:30:13 -0300 |
|---|---|---|
| committer | Gleb Natapov <gleb@redhat.com> | 2013-05-08 12:47:43 +0300 |
| commit | 42bdf991f4cad9678ee2b98c5c2e9299a3f986ef (patch) | |
| tree | b0b91769efbecf318e968477cb1b7cc68d0defbd /arch/x86/kvm | |
| parent | 5af43c24ca59a448c9312dd4a4a51d27ec3b9a73 (diff) | |
| download | lwn-42bdf991f4cad9678ee2b98c5c2e9299a3f986ef.tar.gz lwn-42bdf991f4cad9678ee2b98c5c2e9299a3f986ef.zip | |
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>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/x86.c | 40 |
1 files changed, 20 insertions, 20 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 05a8b1a2300d..094b5d96ab14 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -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; |