From 42bdf991f4cad9678ee2b98c5c2e9299a3f986ef Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Mon, 15 Apr 2013 23:30:13 -0300 Subject: [PATCH] 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 Signed-off-by: Marcelo Tosatti Reviewed-by: Paolo Bonzini Signed-off-by: Gleb Natapov --- arch/x86/kvm/x86.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 05a8b1a..094b5d9 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; -- 2.7.4