All MSR intercepts are enabled by default, so I don't think this patch does anything at all, unless I'm missing some context. On Tue, Jan 30, 2018 at 5:21 AM, Mihai Carabas <mihai.carabas@xxxxxxxxxx> wrote: > Hello Paolo, > > I've back ported this patch on 4.1, after adding the per-vcpu MSR bitmap. > Also enabled the SPEC_CTRL_MSR intercept if qemu instructed so [1]. > > Reviewed-by: Mihai Carabas <mihai.carabas@xxxxxxxxxx> > > [1] > +++ b/arch/x86/kvm/vmx.c > @@ -8391,6 +8391,16 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm > *kvm, unsigned int id) > vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PRED_CMD, > MSR_TYPE_R | MSR_TYPE_W); > vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_BNDCFGS, > MSR_TYPE_R | MSR_TYPE_W); > > + /* > + * If the physical CPU or the vCPU of this VM doesn't > + * support SPEC_CTRL feature, catch each access to it. > + */ > + if (!static_cpu_has(X86_FEATURE_SPEC_CTRL) || > + !guest_cpuid_has_spec_ctrl(&vmx->vcpu)) > + vmx_enable_intercept_for_msr( > + msr_bitmap, > + MSR_IA32_SPEC_CTRL, > + MSR_TYPE_R | MSR_TYPE_W); > > /* > * If PML is turned on, failure on enabling PML just results in > failure > > > > On 09.01.2018 14:03, Paolo Bonzini wrote: >> >> MSR_IA32_SPEC_CTRL is not available unless CPU[7,0].EDX[26] is 1. >> Check that against host CPUID or guest CPUID, respectively for >> host-initiated and guest-initiated accesses. >> >> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx> >> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> >> --- >> This is for after X86_FEATURE_SPEC_CTRL is added to Linux, but >> I still wanted to ack Jim's improvement. >> >> arch/x86/kvm/svm.c | 8 ++++++++ >> arch/x86/kvm/vmx.c | 8 ++++++++ >> 2 files changed, 16 insertions(+) >> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 97126c2bd663..3a646580d7c5 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -3648,6 +3648,10 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr_info) >> msr_info->data = svm->nested.vm_cr_msr; >> break; >> case MSR_IA32_SPEC_CTRL: >> + if (!static_cpu_has(X86_FEATURE_SPEC_CTRL) || >> + (!msr_info->host_initiated && >> + !guest_cpuid_has(vcpu, >> X86_FEATURE_SPEC_CTRL))) >> + return 1; >> msr_info->data = svm->spec_ctrl; >> break; >> case MSR_IA32_UCODE_REV: >> @@ -3806,6 +3810,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr) >> vcpu_unimpl(vcpu, "unimplemented wrmsr: 0x%x data >> 0x%llx\n", ecx, data); >> break; >> case MSR_IA32_SPEC_CTRL: >> + if (!static_cpu_has(X86_FEATURE_SPEC_CTRL) || >> + (!msr_info->host_initiated && >> + !guest_cpuid_has(vcpu, >> X86_FEATURE_SPEC_CTRL))) >> + return 1; >> svm->spec_ctrl = data; >> break; >> case MSR_IA32_APICBASE: >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 49b4a2d61603..42bc7ee293e4 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -3368,6 +3368,10 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr_info) >> msr_info->data = guest_read_tsc(vcpu); >> break; >> case MSR_IA32_SPEC_CTRL: >> + if (!static_cpu_has(X86_FEATURE_SPEC_CTRL) || >> + (!msr_info->host_initiated && >> + !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))) >> + return 1; >> msr_info->data = to_vmx(vcpu)->spec_ctrl; >> break; >> case MSR_IA32_SYSENTER_CS: >> @@ -3510,6 +3514,10 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, >> struct msr_data *msr_info) >> kvm_write_tsc(vcpu, msr_info); >> break; >> case MSR_IA32_SPEC_CTRL: >> + if (!static_cpu_has(X86_FEATURE_SPEC_CTRL) || >> + (!msr_info->host_initiated && >> + !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))) >> + return 1; >> to_vmx(vcpu)->spec_ctrl = data; >> break; >> case MSR_IA32_CR_PAT: >> >
