From d1d93fa90f1afa926cb060b7f78ab01a65705b4d Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Sat, 24 Feb 2018 00:18:20 +0100 Subject: [PATCH] KVM: SVM: Add MSR-based feature support for serializing LFENCE MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In order to determine if LFENCE is a serializing instruction on AMD processors, MSR 0xc0011029 (MSR_F10H_DECFG) must be read and the state of bit 1 checked. This patch will add support to allow a guest to properly make this determination. Add the MSR feature callback operation to svm.c and add MSR 0xc0011029 to the list of MSR-based features. If LFENCE is serializing, then the feature is supported, allowing the hypervisor to set the value of the MSR that guest will see. Support is also added to write (hypervisor only) and read the MSR value for the guest. A write by the guest will result in a #GP. A read by the guest will return the value as set by the host. In this way, the support to expose the feature to the guest is controlled by the hypervisor. Reviewed-by: Paolo Bonzini Signed-off-by: Tom Lendacky Signed-off-by: Paolo Bonzini Signed-off-by: Radim Krčmář --- arch/x86/kvm/svm.c | 36 +++++++++++++++++++++++++++++++++++- arch/x86/kvm/x86.c | 1 + 2 files changed, 36 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index d8db947acf70..f874798f8209 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -178,6 +178,8 @@ struct vcpu_svm { uint64_t sysenter_eip; uint64_t tsc_aux; + u64 msr_decfg; + u64 next_rip; u64 host_user_msrs[NR_HOST_SAVE_USER_MSRS]; @@ -3871,7 +3873,18 @@ static int cr8_write_interception(struct vcpu_svm *svm) static int svm_get_msr_feature(struct kvm_msr_entry *msr) { - return 1; + msr->data = 0; + + switch (msr->index) { + case MSR_F10H_DECFG: + if (boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) + msr->data |= MSR_F10H_DECFG_LFENCE_SERIALIZE; + break; + default: + return 1; + } + + return 0; } static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) @@ -3969,6 +3982,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) msr_info->data = 0x1E; } break; + case MSR_F10H_DECFG: + msr_info->data = svm->msr_decfg; + break; default: return kvm_get_msr_common(vcpu, msr_info); } @@ -4147,6 +4163,24 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) case MSR_VM_IGNNE: vcpu_unimpl(vcpu, "unimplemented wrmsr: 0x%x data 0x%llx\n", ecx, data); break; + case MSR_F10H_DECFG: { + struct kvm_msr_entry msr_entry; + + msr_entry.index = msr->index; + if (svm_get_msr_feature(&msr_entry)) + return 1; + + /* Check the supported bits */ + if (data & ~msr_entry.data) + return 1; + + /* Don't allow the guest to change a bit, #GP */ + if (!msr->host_initiated && (data ^ msr_entry.data)) + return 1; + + svm->msr_decfg = data; + break; + } case MSR_IA32_APICBASE: if (kvm_vcpu_apicv_active(vcpu)) avic_update_vapic_bar(to_svm(vcpu), data); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 239fc1fd7845..54b4ed55945b 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1054,6 +1054,7 @@ static unsigned num_emulated_msrs; * can be used by a hypervisor to validate requested CPU features. */ static u32 msr_based_features[] = { + MSR_F10H_DECFG, }; static unsigned int num_msr_based_features;