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Wed, 30 Dec 2020 08:08:15 -0800 (PST) Date: Wed, 30 Dec 2020 08:08:07 -0800 From: Sean Christopherson To: Borislav Petkov Cc: Babu Moger , pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, fenghua.yu@intel.com, tony.luck@intel.com, wanpengli@tencent.com, kvm@vger.kernel.org, thomas.lendacky@amd.com, peterz@infradead.org, joro@8bytes.org, x86@kernel.org, kyung.min.park@intel.com, linux-kernel@vger.kernel.org, krish.sadhukhan@oracle.com, hpa@zytor.com, mgross@linux.intel.com, vkuznets@redhat.com, kim.phillips@amd.com, wei.huang2@amd.com, jmattson@google.com Subject: Re: [PATCH v2 2/2] KVM: SVM: Add support for Virtual SPEC_CTRL Message-ID: References: <160867624053.3471.7106539070175910424.stgit@bmoger-ubuntu> <160867631505.3471.3808049369257008114.stgit@bmoger-ubuntu> <20201230071501.GB22022@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201230071501.GB22022@zn.tnic> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Dec 30, 2020, Borislav Petkov wrote: > On Tue, Dec 22, 2020 at 04:31:55PM -0600, Babu Moger wrote: > > @@ -2549,7 +2559,10 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > > !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) > > return 1; > > > > - msr_info->data = svm->spec_ctrl; > > + if (static_cpu_has(X86_FEATURE_V_SPEC_CTRL)) > > + msr_info->data = svm->vmcb->save.spec_ctrl; > > + else > > + msr_info->data = svm->spec_ctrl; > > break; > > case MSR_AMD64_VIRT_SPEC_CTRL: > > if (!msr_info->host_initiated && > > @@ -2640,6 +2653,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) > > return 1; > > > > svm->spec_ctrl = data; > > + if (static_cpu_has(X86_FEATURE_V_SPEC_CTRL)) > > + svm->vmcb->save.spec_ctrl = data; > > if (!data) > > break; > > > > Are the get/set_msr() accessors such a fast path that they need > static_cpu_has() ? Nope, they can definitely use boot_cpu_has().