On 30.01.2018 18:33, Jim Mattson wrote:
All MSR intercepts are enabled by default, so I don't think this patch does anything at all, unless I'm missing some context.
Currently on upstream some MSR are intercepted: https://github.com/torvalds/linux/blob/master/arch/x86/kvm/vmx.c#L6838
In particular to this patch, the MSR_IA32_SPEC_CTRL intercept is disabled in 3/8: https://patchwork.kernel.org/patch/10151889/
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:
