On Wed, 2023-07-19 at 22:41 +0800, Binbin Wu wrote: > Use the governed feature framework to track if Linear Address Masking (LAM) > is "enabled", i.e. if LAM can be used by the guest. So that guest_can_use() > can be used to support LAM virtualization. Better to explain why to use governed feature for LAM? Is it because there's hot path(s) calling guest_cpuid_has()? Anyway some context of why can help here. > > LAM modifies the checking that is applied to 64-bit linear addresses, allowing > software to use of the untranslated address bits for metadata and masks the > metadata bits before using them as linear addresses to access memory. > > Signed-off-by: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> > --- > arch/x86/kvm/governed_features.h | 2 ++ > arch/x86/kvm/vmx/vmx.c | 3 +++ > 2 files changed, 5 insertions(+) > > diff --git a/arch/x86/kvm/governed_features.h b/arch/x86/kvm/governed_features.h > index 40ce8e6608cd..708578d60e6f 100644 > --- a/arch/x86/kvm/governed_features.h > +++ b/arch/x86/kvm/governed_features.h > @@ -5,5 +5,7 @@ BUILD_BUG() > > #define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x) > > +KVM_GOVERNED_X86_FEATURE(LAM) > + > #undef KVM_GOVERNED_X86_FEATURE > #undef KVM_GOVERNED_FEATURE > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 0ecf4be2c6af..ae47303c88d7 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7783,6 +7783,9 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > vmx->msr_ia32_feature_control_valid_bits &= > ~FEAT_CTL_SGX_LC_ENABLED; > > + if (boot_cpu_has(X86_FEATURE_LAM)) > + kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_LAM); > + If you want to use boot_cpu_has(), it's better to be done at your last patch to only set the cap bit when boot_cpu_has() is true, I suppose. > /* Refresh #PF interception to account for MAXPHYADDR changes. */ > vmx_update_exception_bitmap(vcpu); > }
