Messages in this thread | | | Date | Fri, 12 Jan 2018 11:08:18 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 5/5] x86/feature: Detect the x86 feature Indirect Branch Prediction Barrier |
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On Thu, Jan 11, 2018 at 05:32:19PM -0800, Ashok Raj wrote: > @@ -1711,11 +1715,18 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu) > __free_pages(virt_to_page(svm->nested.msrpm), MSRPM_ALLOC_ORDER); > kvm_vcpu_uninit(vcpu); > kmem_cache_free(kvm_vcpu_cache, svm); > + /* > + * The VMCB could be recycled, causing a false negative in svm_vcpu_load; > + * block speculative execution. > + */ > + if (boot_cpu_has(X86_FEATURE_PRED_CMD)) > + native_wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB); > }
> @@ -3837,6 +3839,12 @@ static void free_loaded_vmcs(struct loaded_vmcs *loaded_vmcs) > free_vmcs(loaded_vmcs->vmcs); > loaded_vmcs->vmcs = NULL; > WARN_ON(loaded_vmcs->shadow_vmcs != NULL); > + /* > + * The VMCS could be recycled, causing a false negative in vmx_vcpu_load > + * block speculative execution. > + */ > + if (boot_cpu_has(X86_FEATURE_SPEC_CTRL)) > + native_wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB); > }
Whitespace damage.
Also, why not introduce a helper like:
static inline flush_ibpb(void) { if (static_cpu_has(X86_FEATURE_SPEC_CTRL)) native_write_msr(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB); }
?
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