Messages in this thread | | | Date | Mon, 30 Jan 2023 14:33:28 +0800 | Subject | Re: [PATCH v2 03/15] KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS | From | "Yang, Weijiang" <> |
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On 1/27/2023 3:50 AM, Sean Christopherson wrote: > On Thu, Nov 24, 2022, Yang Weijiang wrote: >> Updated CPUID.0xD.0x1, which reports the current required storage size >> of all features enabled via XCR0 | XSS, when the guest's XSS is modified. >> >> Note, KVM does not yet support any XSS based features, i.e. supported_xss >> is guaranteed to be zero at this time. >> >> Co-developed-by: Zhang Yi Z <yi.z.zhang@linux.intel.com> >> Signed-off-by: Zhang Yi Z <yi.z.zhang@linux.intel.com> >> Signed-off-by: Yang Weijiang <weijiang.yang@intel.com> >> --- >> arch/x86/kvm/cpuid.c | 16 +++++++++++++--- >> arch/x86/kvm/x86.c | 6 ++++-- >> 2 files changed, 17 insertions(+), 5 deletions(-) >> >> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c >> index 6b5912578edd..85e3df6217af 100644 >> --- a/arch/x86/kvm/cpuid.c >> +++ b/arch/x86/kvm/cpuid.c >> @@ -272,9 +272,19 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e >> best->ebx = xstate_required_size(vcpu->arch.xcr0, false); >> >> best = cpuid_entry2_find(entries, nent, 0xD, 1); >> - if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) || >> - cpuid_entry_has(best, X86_FEATURE_XSAVEC))) >> - best->ebx = xstate_required_size(vcpu->arch.xcr0, true); >> + if (best) { >> + if (cpuid_entry_has(best, X86_FEATURE_XSAVES) || >> + cpuid_entry_has(best, X86_FEATURE_XSAVEC)) { >> + u64 xstate = vcpu->arch.xcr0 | vcpu->arch.ia32_xss; >> + >> + best->ebx = xstate_required_size(xstate, true); >> + } >> + >> + if (!cpuid_entry_has(best, X86_FEATURE_XSAVES)) { >> + best->ecx = 0; >> + best->edx = 0; > ECX and EDX should be left alone, it is userspace's responsibility to provide a > sane CPUID model. E.g. KVM doesn't clear EBX or EDX in CPUID.0xD.0x1 when XSAVE > is unsupported.
Thanks for review!
Sure, I'll remove it.
> >> + } >> + } >> >> best = __kvm_find_kvm_cpuid_features(vcpu, entries, nent); >> if (kvm_hlt_in_guest(vcpu->kvm) && best && >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 16726b44061b..888a153e32bc 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -3685,8 +3685,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) >> */ >> if (data & ~kvm_caps.supported_xss) >> return 1; >> - vcpu->arch.ia32_xss = data; >> - kvm_update_cpuid_runtime(vcpu); >> + if (vcpu->arch.ia32_xss != data) { >> + vcpu->arch.ia32_xss = data; >> + kvm_update_cpuid_runtime(vcpu); >> + } >> break; >> case MSR_SMI_COUNT: >> if (!msr_info->host_initiated) >> -- >> 2.27.0 >>
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