On Fri, 2024-05-17 at 10:39 -0700, Sean Christopherson wrote: > Drop the manual boot_cpu_has() checks on XSAVE when adjusting the guest's > XSAVES capabilities now that guest cpu_caps incorporates KVM's support. > The guest's cpu_caps are initialized from kvm_cpu_caps, which are in turn > initialized from boot_cpu_data, i.e. checking guest_cpu_cap_has() also > checks host/KVM capabilities (which is the entire point of cpu_caps). > > Cc: Maxim Levitsky <mlevitsk@xxxxxxxxxx> > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > --- > arch/x86/kvm/svm/svm.c | 1 - > arch/x86/kvm/vmx/vmx.c | 3 +-- > 2 files changed, 1 insertion(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 06770b60c0ba..4aaffbf22531 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -4340,7 +4340,6 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > * the guest read/write access to the host's XSS. > */ > guest_cpu_cap_change(vcpu, X86_FEATURE_XSAVES, > - boot_cpu_has(X86_FEATURE_XSAVE) && > boot_cpu_has(X86_FEATURE_XSAVES) && > guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVE)); > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 741961a1edcc..6fbdf520c58b 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7833,8 +7833,7 @@ void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > * to the guest. XSAVES depends on CR4.OSXSAVE, and CR4.OSXSAVE can be > * set if and only if XSAVE is supported. > */ > - if (!boot_cpu_has(X86_FEATURE_XSAVE) || > - !guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVE)) > + if (!guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVE)) > guest_cpu_cap_clear(vcpu, X86_FEATURE_XSAVES); Hi, I have a question about this code, even before the patch was applied: While it is obviously correct to disable XSAVES when XSAVE not supported, I wonder: There are a lot more cases like that and KVM explicitly doesn't bother checking them, e.g all of the AVX family also depends on XSAVE due to XCR0. What makes XSAVES/XSAVE dependency special here? Maybe we can remove this code to be consistent? AMD portion of this patch, on the other hand does makes sense, due to a lack of a separate XSAVES intercept. Best regards, Maxim Levitsky > > vmx_setup_uret_msrs(vmx);
