Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751352AbeAIMFx (ORCPT + 1 other); Tue, 9 Jan 2018 07:05:53 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:38280 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751255AbeAIMDW (ORCPT ); Tue, 9 Jan 2018 07:03:22 -0500 X-Google-Smtp-Source: ACJfBov2ZZyT8grt9bWZD+7ogpgpe9EzkE3ZGjJjwCNEsGHOk43OI1YTMXKRgFhTe/Ty4PtC+zj4aQ== From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: rkrcmar@redhat.com, liran.alon@oracle.com, jmattson@google.com, aliguori@amazon.com, thomas.lendacky@amd.com, dwmw@amazon.co.uk, bp@alien8.de, x86@kernel.org Subject: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest Date: Tue, 9 Jan 2018 13:03:05 +0100 Message-Id: <20180109120311.27565-4-pbonzini@redhat.com> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180109120311.27565-1-pbonzini@redhat.com> References: <20180109120311.27565-1-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Direct access to MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD is important for performance. Allow load/store of MSR_IA32_SPEC_CTRL, restore guest IBRS on VM entry and set it to 0 on VM exit (because Linux does not use it yet). Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 669f5f74857d..ef603692aa98 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -120,6 +120,8 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO); #endif +static bool __read_mostly have_spec_ctrl; + #define KVM_GUEST_CR0_MASK (X86_CR0_NW | X86_CR0_CD) #define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST (X86_CR0_WP | X86_CR0_NE) #define KVM_VM_CR0_ALWAYS_ON \ @@ -609,6 +611,8 @@ struct vcpu_vmx { u64 msr_host_kernel_gs_base; u64 msr_guest_kernel_gs_base; #endif + u64 spec_ctrl; + u32 vm_entry_controls_shadow; u32 vm_exit_controls_shadow; u32 secondary_exec_control; @@ -3361,6 +3365,9 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_IA32_TSC: msr_info->data = guest_read_tsc(vcpu); break; + case MSR_IA32_SPEC_CTRL: + msr_info->data = to_vmx(vcpu)->spec_ctrl; + break; case MSR_IA32_SYSENTER_CS: msr_info->data = vmcs_read32(GUEST_SYSENTER_CS); break; @@ -3500,6 +3507,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) case MSR_IA32_TSC: kvm_write_tsc(vcpu, msr_info); break; + case MSR_IA32_SPEC_CTRL: + to_vmx(vcpu)->spec_ctrl = data; + break; case MSR_IA32_CR_PAT: if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) { if (!kvm_mtrr_valid(vcpu, MSR_IA32_CR_PAT, data)) @@ -7062,6 +7072,17 @@ static __init int hardware_setup(void) goto out; } + /* + * FIXME: this is only needed until SPEC_CTRL is supported + * by upstream Linux in cpufeatures, then it can be replaced + * with static_cpu_has. + */ + have_spec_ctrl = cpu_has_spec_ctrl(); + if (have_spec_ctrl) + pr_info("kvm: SPEC_CTRL available\n"); + else + pr_info("kvm: SPEC_CTRL not available\n"); + if (boot_cpu_has(X86_FEATURE_NX)) kvm_enable_efer_bits(EFER_NX); @@ -7131,6 +7152,8 @@ static __init int hardware_setup(void) vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_CS, false); vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_ESP, false); vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false); + vmx_disable_intercept_for_msr(MSR_IA32_SPEC_CTRL, false); + vmx_disable_intercept_for_msr(MSR_IA32_PRED_CMD, false); memcpy(vmx_msr_bitmap_legacy_x2apic_apicv, vmx_msr_bitmap_legacy, PAGE_SIZE); @@ -9601,6 +9624,13 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) vmx_arm_hv_timer(vcpu); + /* + * MSR_IA32_SPEC_CTRL is restored after the last indirect branch + * before vmentry. + */ + if (have_spec_ctrl && vmx->spec_ctrl != 0) + wrmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl); + vmx->__launched = vmx->loaded_vmcs->launched; asm( /* Store host registers */ @@ -9707,6 +9737,18 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu) #endif ); + if (have_spec_ctrl) { + rdmsrl(MSR_IA32_SPEC_CTRL, vmx->spec_ctrl); + if (vmx->spec_ctrl != 0) + wrmsrl(MSR_IA32_SPEC_CTRL, 0); + } + /* + * Speculative execution past the above wrmsrl might encounter + * an indirect branch and use guest-controlled contents of the + * indirect branch predictor; block it. + */ + asm("lfence"); + /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */ if (vmx->host_debugctlmsr) update_debugctlmsr(vmx->host_debugctlmsr); -- 1.8.3.1