| Message ID | 20210921000303.400537-5-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Clean up RESET "emulation" | expand |
Sean Christopherson <seanjc@google.com> writes: > Drop code to set CR0.ET for the guest during initialization of the guest > FPU. The code was added as a misguided bug fix by commit 380102c8e431 > ("KVM Set the ET flag in CR0 after initializing FX") to resolve an issue > where vcpu->cr0 (now vcpu->arch.cr0) was not correctly initialized on SVM > systems. While init_vmcb() did set CR0.ET, it only did so in the VMCB, > and subtly did not update vcpu->cr0. Stuffing CR0.ET worked around the > immediate problem, but did not fix the real bug of vcpu->cr0 and the VMCB > being out of sync. That underlying bug was eventually remedied by commit > 18fa000ae453 ("KVM: SVM: Reset cr0 properly on vcpu reset"). > > No functional change intended. fx_init() is only called from kvm_arch_vcpu_create() (and inlined later in the series) a few lines before kvm_vcpu_reset() which stuffs CR0 with X86_CR0_ET too and it doesn't seem that arch.cr0 value is important in between. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/x86.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index ab907a0b9eeb..e0bff5473813 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -10628,8 +10628,6 @@ static void fx_init(struct kvm_vcpu *vcpu) > * Ensure guest xcr0 is valid for loading > */ > vcpu->arch.xcr0 = XFEATURE_MASK_FP; > - > - vcpu->arch.cr0 |= X86_CR0_ET; > } > > void kvm_free_guest_fpu(struct kvm_vcpu *vcpu) Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index ab907a0b9eeb..e0bff5473813 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10628,8 +10628,6 @@ static void fx_init(struct kvm_vcpu *vcpu) * Ensure guest xcr0 is valid for loading */ vcpu->arch.xcr0 = XFEATURE_MASK_FP; - - vcpu->arch.cr0 |= X86_CR0_ET; } void kvm_free_guest_fpu(struct kvm_vcpu *vcpu)
Drop code to set CR0.ET for the guest during initialization of the guest FPU. The code was added as a misguided bug fix by commit 380102c8e431 ("KVM Set the ET flag in CR0 after initializing FX") to resolve an issue where vcpu->cr0 (now vcpu->arch.cr0) was not correctly initialized on SVM systems. While init_vmcb() did set CR0.ET, it only did so in the VMCB, and subtly did not update vcpu->cr0. Stuffing CR0.ET worked around the immediate problem, but did not fix the real bug of vcpu->cr0 and the VMCB being out of sync. That underlying bug was eventually remedied by commit 18fa000ae453 ("KVM: SVM: Reset cr0 properly on vcpu reset"). No functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 2 -- 1 file changed, 2 deletions(-)