On Wed, Mar 03, 2021, Like Xu wrote: > If CPUID.(EAX=07H, ECX=0):EDX[19] is set to 1, then KVM supports Arch > LBRs and CPUID leaf 01CH indicates details of the Arch LBRs capabilities. > Currently, KVM only supports the current host LBR depth for guests, > which is also the maximum supported depth on the host. > > Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx> > --- > arch/x86/kvm/cpuid.c | 25 ++++++++++++++++++++++++- > arch/x86/kvm/vmx/vmx.c | 2 ++ > 2 files changed, 26 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index b4247f821277..4473324fe7be 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -450,7 +450,7 @@ void kvm_set_cpu_caps(void) > F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | > F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) | > F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) | > - F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) > + F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) | F(ARCH_LBR) > ); > > /* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */ ... > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 2f307689a14b..034708a3df20 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7258,6 +7258,8 @@ static __init void vmx_set_cpu_caps(void) > kvm_cpu_cap_clear(X86_FEATURE_INVPCID); > if (vmx_pt_mode_is_host_guest()) > kvm_cpu_cap_check_and_set(X86_FEATURE_INTEL_PT); > + if (cpu_has_vmx_arch_lbr()) > + kvm_cpu_cap_check_and_set(X86_FEATURE_ARCH_LBR); Using kvm_cpu_cap_check_and_set(), which queries boot_cpu_has(), is only necessary if a feature is not exposed by default in kvm_set_cpu_caps(). That's why INTEL_PT uses it. ARCH_LBR on the other hand is set in the "enable by default" mask. That being said, it's probably a bad idea to advertise ARCH_LBR by default. In the unlikely case that AMD adds support for ARCH_LBR, enable-by-default means guest will be able to use ARCH_LBR on old KVMs that presumably would lack support for ARCH_LBR on SVM. TL;DR: omit F(ARCH_LBR) or replace it with "0 /* ARCH_LBR */". > if (vmx_umip_emulated()) > kvm_cpu_cap_set(X86_FEATURE_UMIP); > -- > 2.29.2 >
