From: Yang Weijiang Update CPUID.(EAX=0DH,ECX=1).EBX to reflect current required xstate size due to XSS MSR modification. CPUID(EAX=0DH,ECX=1).EBX reports the required storage size of all enabled xstate features in (XCR0 | IA32_XSS). The CPUID value can be used by guest before allocate sufficient xsave buffer. Note, KVM does not yet support any XSS based features, i.e. supported_xss is guaranteed to be zero at this time. Opportunistically return KVM_MSR_RET_UNSUPPORTED if guest CPUID doesn't enumerate it. Since KVM_MSR_RET_UNSUPPORTED takes care of host_initiated cases, drop the host_initiated check. Suggested-by: Sean Christopherson Co-developed-by: Zhang Yi Z Signed-off-by: Zhang Yi Z Signed-off-by: Yang Weijiang Reviewed-by: Maxim Levitsky Reviewed-by: Chao Gao Tested-by: Mathias Krause Tested-by: John Allen Signed-off-by: Chao Gao --- arch/x86/include/asm/kvm_host.h | 3 ++- arch/x86/kvm/cpuid.c | 15 ++++++++++++++- arch/x86/kvm/x86.c | 9 +++++---- 3 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 39b93642e7d2..1faf53df6259 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -811,7 +811,6 @@ struct kvm_vcpu_arch { bool at_instruction_boundary; bool tpr_access_reporting; bool xfd_no_write_intercept; - u64 ia32_xss; u64 microcode_version; u64 arch_capabilities; u64 perf_capabilities; @@ -872,6 +871,8 @@ struct kvm_vcpu_arch { u64 xcr0; u64 guest_supported_xcr0; + u64 guest_supported_xss; + u64 ia32_xss; struct kvm_pio_request pio; void *pio_data; diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 30fd18700972..85079caaf507 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -263,6 +263,17 @@ static u64 cpuid_get_supported_xcr0(struct kvm_vcpu *vcpu) return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0; } +static u64 cpuid_get_supported_xss(struct kvm_vcpu *vcpu) +{ + struct kvm_cpuid_entry2 *best; + + best = kvm_find_cpuid_entry_index(vcpu, 0xd, 1); + if (!best) + return 0; + + return (best->ecx | ((u64)best->edx << 32)) & kvm_caps.supported_xss; +} + static __always_inline void kvm_update_feature_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *entry, unsigned int x86_feature, @@ -305,7 +316,8 @@ static void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) best = kvm_find_cpuid_entry_index(vcpu, 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); + best->ebx = xstate_required_size(vcpu->arch.xcr0 | + vcpu->arch.ia32_xss, true); } static bool kvm_cpuid_has_hyperv(struct kvm_vcpu *vcpu) @@ -424,6 +436,7 @@ void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) } vcpu->arch.guest_supported_xcr0 = cpuid_get_supported_xcr0(vcpu); + vcpu->arch.guest_supported_xss = cpuid_get_supported_xss(vcpu); vcpu->arch.pv_cpuid.features = kvm_apply_cpuid_pv_features_quirk(vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e0e440607e02..c91472d36717 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3998,16 +3998,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) } break; case MSR_IA32_XSS: - if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_XSAVES)) - return 1; + if (!guest_cpuid_has(vcpu, X86_FEATURE_XSAVES)) + return KVM_MSR_RET_UNSUPPORTED; /* * KVM supports exposing PT to the guest, but does not support * IA32_XSS[bit 8]. Guests have to use RDMSR/WRMSR rather than * XSAVES/XRSTORS to save/restore PT MSRs. */ - if (data & ~kvm_caps.supported_xss) + if (data & ~vcpu->arch.guest_supported_xss) return 1; + if (vcpu->arch.ia32_xss == data) + break; vcpu->arch.ia32_xss = data; vcpu->arch.cpuid_dynamic_bits_dirty = true; break; -- 2.47.1