From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liran Alon Subject: Re: [PATCH 1/7] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT accessors Date: Mon, 08 Jan 2018 21:09:14 +0200 Message-ID: <5A53C1DA.50901@ORACLE.COM> References: <1515434925-10250-1-git-send-email-pbonzini@redhat.com> <1515434925-10250-2-git-send-email-pbonzini@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: jmattson@google.com, aliguori@amazon.com, thomas.lendacky@amd.com, dwmw@amazon.co.uk, bp@alien8.de To: Paolo Bonzini , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Return-path: In-Reply-To: <1515434925-10250-2-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 08/01/18 20:08, Paolo Bonzini wrote: > As an interim measure until SPEC_CTRL is supported by upstream > Linux in cpufeatures, add a function that lets vmx.c and svm.c > know whether to save/restore MSR_IA32_SPEC_CTRL. > > Signed-off-by: Paolo Bonzini > --- > arch/x86/kvm/cpuid.c | 3 --- > arch/x86/kvm/cpuid.h | 22 ++++++++++++++++++++++ > 2 files changed, 22 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index 8e9a07c557f1..767af697c20c 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -67,9 +67,6 @@ u64 kvm_supported_xcr0(void) > > #define F(x) bit(X86_FEATURE_##x) > > -/* These are scattered features in cpufeatures.h. */ > -#define KVM_CPUID_BIT_AVX512_4VNNIW 2 > -#define KVM_CPUID_BIT_AVX512_4FMAPS 3 > #define KF(x) bit(KVM_CPUID_BIT_##x) > > int kvm_update_cpuid(struct kvm_vcpu *vcpu) > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h > index c2cea6651279..8d04ccf177ce 100644 > --- a/arch/x86/kvm/cpuid.h > +++ b/arch/x86/kvm/cpuid.h > @@ -155,6 +155,28 @@ static inline int guest_cpuid_stepping(struct kvm_vcpu *vcpu) > return x86_stepping(best->eax); > } > > +/* These are scattered features in cpufeatures.h. */ > +#define KVM_CPUID_BIT_AVX512_4VNNIW 2 > +#define KVM_CPUID_BIT_AVX512_4FMAPS 3 > +#define KVM_CPUID_BIT_SPEC_CTRL 26 > +#define KVM_CPUID_BIT_STIBP 27 > + > +/* CPUID[eax=0x80000008].ebx */ > +#define KVM_CPUID_BIT_IBPB_SUPPORT 12 > + > +static inline bool cpu_has_spec_ctrl(void) > +{ > + u32 eax, ebx, ecx, edx; > + cpuid_count(7, 0, &eax, &ebx, &ecx, &edx); > + > + return edx & bit(KVM_CPUID_BIT_SPEC_CTRL); Why not just "return cpuid_edx(7) & bit(KVM_CPUID_BIT_SPEC_CTRL);"? This is also consistent with how cpu_has_ibpb_support() is written. > +} > + > +static inline bool cpu_has_ibpb_support(void) > +{ > + return cpuid_ebx(0x80000008) & bit(KVM_CPUID_BIT_IBPB_SUPPORT); > +} > + > static inline bool supports_cpuid_fault(struct kvm_vcpu *vcpu) > { > return vcpu->arch.msr_platform_info & MSR_PLATFORM_INFO_CPUID_FAULT; >