Messages in this thread Patch in this message | | | Date | Thu, 18 May 2023 17:32:31 +0800 | Subject | Re: [PATCH] KVM: x86: Track supported ARCH_CAPABILITIES in kvm_caps | From | Xiaoyao Li <> |
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On 5/6/2023 11:04 AM, Chao Gao wrote: > to avoid computing the supported value at runtime every time. > > No functional change intended.
the value of kvm_get_arch_capabilities() can be changed due to
if (l1tf_vmx_mitigation != VMENTER_L1D_FLUSH_NEVER) data |= ARCH_CAP_SKIP_VMENTRY_L1DFLUSH;
and l1tf_vmx_mitigation can be runtime changed by vmentry_l1d_flush module param.
We need a detailed analysis that in no real case can ARCH_CAP_SKIP_VMENTRY_L1DFLUSH bit change runtime.
> Signed-off-by: Chao Gao <chao.gao@intel.com> > --- > > A new call site of kvm_get_arch_capabilities() is added by [1]. It should be > replaced with the cached value in kvm_caps. > > [1] https://lore.kernel.org/all/20230504181827.130532-1-mizhang@google.com/ > > > arch/x86/kvm/x86.c | 5 +++-- > arch/x86/kvm/x86.h | 1 + > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 523c39a03c00..94aa70ec169c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1670,7 +1670,7 @@ static int kvm_get_msr_feature(struct kvm_msr_entry *msr) > { > switch (msr->index) { > case MSR_IA32_ARCH_CAPABILITIES: > - msr->data = kvm_get_arch_capabilities(); > + msr->data = kvm_caps.supported_arch_cap; > break; > case MSR_IA32_PERF_CAPABILITIES: > msr->data = kvm_caps.supported_perf_cap; > @@ -9523,6 +9523,7 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) > kvm_caps.max_guest_tsc_khz = max; > } > kvm_caps.default_tsc_scaling_ratio = 1ULL << kvm_caps.tsc_scaling_ratio_frac_bits; > + kvm_caps.supported_arch_cap = kvm_get_arch_capabilities(); > kvm_init_msr_lists(); > return 0; > > @@ -11879,7 +11880,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) > if (r) > goto free_guest_fpu; > > - vcpu->arch.arch_capabilities = kvm_get_arch_capabilities(); > + vcpu->arch.arch_capabilities = kvm_caps.supported_arch_cap; > vcpu->arch.msr_platform_info = MSR_PLATFORM_INFO_CPUID_FAULT; > kvm_xen_init_vcpu(vcpu); > kvm_vcpu_mtrr_init(vcpu); > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index c544602d07a3..d3e524bcc169 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -29,6 +29,7 @@ struct kvm_caps { > u64 supported_xcr0; > u64 supported_xss; > u64 supported_perf_cap; > + u64 supported_arch_cap; > }; > > void kvm_spurious_fault(void); > > base-commit: b3c98052d46948a8d65d2778c7f306ff38366aac
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