On Sun, Jan 28, 2018 at 4:58 PM, KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote: > From: Ashok Raj <ashok.raj@xxxxxxxxx> > > Add MSR passthrough for MSR_IA32_PRED_CMD and place branch predictor > barriers on switching between VMs to avoid inter VM Spectre-v2 attacks. > > [peterz: rebase and changelog rewrite] > [karahmed: - rebase > - vmx: expose PRED_CMD whenever it is available > - svm: only pass through IBPB if it is available] > Cc: Asit Mallick <asit.k.mallick@xxxxxxxxx> > Cc: Dave Hansen <dave.hansen@xxxxxxxxx> > Cc: Arjan Van De Ven <arjan.van.de.ven@xxxxxxxxx> > Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx> > Cc: Jun Nakajima <jun.nakajima@xxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxx> > Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Link: http://lkml.kernel.org/r/1515720739-43819-6-git-send-email-ashok.raj@xxxxxxxxx > Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> > Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx> > --- > arch/x86/kvm/svm.c | 14 ++++++++++++++ > arch/x86/kvm/vmx.c | 4 ++++ > 2 files changed, 18 insertions(+) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 2744b973..c886e46 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -529,6 +529,7 @@ struct svm_cpu_data { > struct kvm_ldttss_desc *tss_desc; > > struct page *save_area; > + struct vmcb *current_vmcb; > }; > > static DEFINE_PER_CPU(struct svm_cpu_data *, svm_data); > @@ -918,6 +919,9 @@ static void svm_vcpu_init_msrpm(u32 *msrpm) > > set_msr_interception(msrpm, direct_access_msrs[i].index, 1, 1); > } > + > + if (boot_cpu_has(X86_FEATURE_IBPB)) > + set_msr_interception(msrpm, MSR_IA32_PRED_CMD, 1, 1); What if the guest doesn't have X86_FEATURE_IBPB? > } > > static void add_msr_offset(u32 offset) > @@ -1706,11 +1710,17 @@ 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 page can be recycled, causing a false negative in > + * svm_vcpu_load(). So do a full IBPB now. > + */ > + indirect_branch_prediction_barrier(); > } > > static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > { > struct vcpu_svm *svm = to_svm(vcpu); > + struct svm_cpu_data *sd = per_cpu(svm_data, cpu); > int i; > > if (unlikely(cpu != vcpu->cpu)) { > @@ -1739,6 +1749,10 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (static_cpu_has(X86_FEATURE_RDTSCP)) > wrmsrl(MSR_TSC_AUX, svm->tsc_aux); > > + if (sd->current_vmcb != svm->vmcb) { > + sd->current_vmcb = svm->vmcb; > + indirect_branch_prediction_barrier(); > + } > avic_vcpu_load(vcpu, cpu); > } > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index dac564d..f82a44c 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -2296,6 +2296,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) { > per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs; > vmcs_load(vmx->loaded_vmcs->vmcs); > + indirect_branch_prediction_barrier(); > } > > if (!already_loaded) { > @@ -9613,6 +9614,9 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) > goto free_msrs; > > msr_bitmap = vmx->vmcs01.msr_bitmap; > + > + if (boot_cpu_has(X86_FEATURE_IBPB)) > + vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PRED_CMD, MSR_TYPE_RW); What if the guest doesn't have X86_FEATURE_IBPB? > vmx_disable_intercept_for_msr(msr_bitmap, MSR_FS_BASE, MSR_TYPE_RW); > vmx_disable_intercept_for_msr(msr_bitmap, MSR_GS_BASE, MSR_TYPE_RW); > vmx_disable_intercept_for_msr(msr_bitmap, MSR_KERNEL_GS_BASE, MSR_TYPE_RW); > -- > 2.7.4 >
