Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755326AbeAHSJy (ORCPT + 1 other); Mon, 8 Jan 2018 13:09:54 -0500 Received: from mail-wr0-f195.google.com ([209.85.128.195]:40917 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755219AbeAHSJB (ORCPT ); Mon, 8 Jan 2018 13:09:01 -0500 X-Google-Smtp-Source: ACJfBoux4ara6W/Iww9gG+/Qv4gA9RPrhUI6ikpe1WSuL0snLljYagz/2FjRch6iK50lEmGYNwRiUg== From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: jmattson@google.com, aliguori@amazon.com, thomas.lendacky@amd.com, dwmw@amazon.co.uk, bp@alien8.de Subject: [PATCH 6/7] x86/svm: Set IBPB when running a different VCPU Date: Mon, 8 Jan 2018 19:08:44 +0100 Message-Id: <1515434925-10250-7-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1515434925-10250-1-git-send-email-pbonzini@redhat.com> References: <1515434925-10250-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Tom Lendacky Set IBPB (Indirect Branch Prediction Barrier) when the current CPU is going to run a VCPU different from what was previously run. Nested virtualization uses the same VMCB for the second level guest, but the L1 hypervisor should be using IBRS to protect itself. Signed-off-by: Tom Lendacky Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 779981a00d01..dd744d896cec 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -289,6 +289,7 @@ struct amd_svm_iommu_ir { module_param(vgif, int, 0444); static bool __read_mostly have_spec_ctrl; +static bool __read_mostly have_ibpb_support; static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0); static void svm_flush_tlb(struct kvm_vcpu *vcpu, bool invalidate_gpa); @@ -540,6 +541,7 @@ 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); @@ -1151,6 +1153,11 @@ static __init int svm_hardware_setup(void) pr_info("kvm: SPEC_CTRL available\n"); else pr_info("kvm: SPEC_CTRL not available\n"); + have_ibpb_support = have_spec_ctrl || cpu_has_ibpb_support(); + if (have_ibpb_support) + pr_info("kvm: IBPB_SUPPORT available\n"); + else + pr_info("kvm: IBPB_SUPPORT not available\n"); return 0; @@ -1725,11 +1732,19 @@ 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 (have_ibpb_support) + wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB); } 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)) { @@ -1758,6 +1773,12 @@ 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; + if (have_ibpb_support) + wrmsrl(MSR_IA32_PRED_CMD, FEATURE_SET_IBPB); + } + avic_vcpu_load(vcpu, cpu); } @@ -2798,6 +2819,11 @@ static int nested_svm_vmexit(struct vcpu_svm *svm) if (!nested_vmcb) return 1; + /* + * No need for IBPB here, the L1 hypervisor should be running with + * IBRS=1 and inserts one already when switching L2 VMs. + */ + /* Exit Guest-Mode */ leave_guest_mode(&svm->vcpu); svm->nested.vmcb = 0; @@ -3061,6 +3087,11 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm) if (!nested_vmcb) return false; + /* + * No need for IBPB here, since the nested VM is less privileged. The + * L1 hypervisor inserts one already when switching L2 VMs. + */ + if (!nested_vmcb_checks(nested_vmcb)) { nested_vmcb->control.exit_code = SVM_EXIT_ERR; nested_vmcb->control.exit_code_hi = 0; -- 1.8.3.1