From e0096d01c4fcb8c96c05643cfc2c20ab78eae4da Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Fri, 15 Sep 2023 15:54:30 -0500 Subject: KVM: SVM: Fix TSC_AUX virtualization setup The checks for virtualizing TSC_AUX occur during the vCPU reset processing path. However, at the time of initial vCPU reset processing, when the vCPU is first created, not all of the guest CPUID information has been set. In this case the RDTSCP and RDPID feature support for the guest is not in place and so TSC_AUX virtualization is not established. This continues for each vCPU created for the guest. On the first boot of an AP, vCPU reset processing is executed as a result of an APIC INIT event, this time with all of the guest CPUID information set, resulting in TSC_AUX virtualization being enabled, but only for the APs. The BSP always sees a TSC_AUX value of 0 which probably went unnoticed because, at least for Linux, the BSP TSC_AUX value is 0. Move the TSC_AUX virtualization enablement out of the init_vmcb() path and into the vcpu_after_set_cpuid() path to allow for proper initialization of the support after the guest CPUID information has been set. With the TSC_AUX virtualization support now in the vcpu_set_after_cpuid() path, the intercepts must be either cleared or set based on the guest CPUID input. Fixes: 296d5a17e793 ("KVM: SEV-ES: Use V_TSC_AUX if available instead of RDTSC/MSR_TSC_AUX intercepts") Signed-off-by: Tom Lendacky Message-Id: <4137fbcb9008951ab5f0befa74a0399d2cce809a.1694811272.git.thomas.lendacky@amd.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/svm.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'arch/x86/kvm/svm/svm.c') diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index f283eb47f6ac..aef1ddf0b705 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4284,7 +4284,6 @@ static bool svm_has_emulated_msr(struct kvm *kvm, u32 index) static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) { struct vcpu_svm *svm = to_svm(vcpu); - struct kvm_cpuid_entry2 *best; /* * SVM doesn't provide a way to disable just XSAVES in the guest, KVM @@ -4328,12 +4327,8 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) set_msr_interception(vcpu, svm->msrpm, MSR_IA32_FLUSH_CMD, 0, !!guest_cpuid_has(vcpu, X86_FEATURE_FLUSH_L1D)); - /* For sev guests, the memory encryption bit is not reserved in CR3. */ - if (sev_guest(vcpu->kvm)) { - best = kvm_find_cpuid_entry(vcpu, 0x8000001F); - if (best) - vcpu->arch.reserved_gpa_bits &= ~(1UL << (best->ebx & 0x3f)); - } + if (sev_guest(vcpu->kvm)) + sev_vcpu_after_set_cpuid(svm); init_vmcb_after_set_cpuid(vcpu); } -- cgit v1.2.3 From 916e3e5f26abc165437950daff370c0693572ef4 Mon Sep 17 00:00:00 2001 From: Tom Lendacky Date: Fri, 15 Sep 2023 15:54:32 -0500 Subject: KVM: SVM: Do not use user return MSR support for virtualized TSC_AUX When the TSC_AUX MSR is virtualized, the TSC_AUX value is swap type "B" within the VMSA. This means that the guest value is loaded on VMRUN and the host value is restored from the host save area on #VMEXIT. Since the value is restored on #VMEXIT, the KVM user return MSR support for TSC_AUX can be replaced by populating the host save area with the current host value of TSC_AUX. And, since TSC_AUX is not changed by Linux post-boot, the host save area can be set once in svm_hardware_enable(). This eliminates the two WRMSR instructions associated with the user return MSR support. Signed-off-by: Tom Lendacky Message-Id: Signed-off-by: Paolo Bonzini --- arch/x86/kvm/svm/svm.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) (limited to 'arch/x86/kvm/svm/svm.c') diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index aef1ddf0b705..9507df93f410 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -683,6 +683,21 @@ static int svm_hardware_enable(void) amd_pmu_enable_virt(); + /* + * If TSC_AUX virtualization is supported, TSC_AUX becomes a swap type + * "B" field (see sev_es_prepare_switch_to_guest()) for SEV-ES guests. + * Since Linux does not change the value of TSC_AUX once set, prime the + * TSC_AUX field now to avoid a RDMSR on every vCPU run. + */ + if (boot_cpu_has(X86_FEATURE_V_TSC_AUX)) { + struct sev_es_save_area *hostsa; + u32 msr_hi; + + hostsa = (struct sev_es_save_area *)(page_address(sd->save_area) + 0x400); + + rdmsr(MSR_TSC_AUX, hostsa->tsc_aux, msr_hi); + } + return 0; } @@ -1532,7 +1547,14 @@ static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu) if (tsc_scaling) __svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio); - if (likely(tsc_aux_uret_slot >= 0)) + /* + * TSC_AUX is always virtualized for SEV-ES guests when the feature is + * available. The user return MSR support is not required in this case + * because TSC_AUX is restored on #VMEXIT from the host save area + * (which has been initialized in svm_hardware_enable()). + */ + if (likely(tsc_aux_uret_slot >= 0) && + (!boot_cpu_has(X86_FEATURE_V_TSC_AUX) || !sev_es_guest(vcpu->kvm))) kvm_set_user_return_msr(tsc_aux_uret_slot, svm->tsc_aux, -1ull); svm->guest_state_loaded = true; @@ -3086,6 +3108,16 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) svm->sysenter_esp_hi = guest_cpuid_is_intel(vcpu) ? (data >> 32) : 0; break; case MSR_TSC_AUX: + /* + * TSC_AUX is always virtualized for SEV-ES guests when the + * feature is available. The user return MSR support is not + * required in this case because TSC_AUX is restored on #VMEXIT + * from the host save area (which has been initialized in + * svm_hardware_enable()). + */ + if (boot_cpu_has(X86_FEATURE_V_TSC_AUX) && sev_es_guest(vcpu->kvm)) + break; + /* * TSC_AUX is usually changed only during boot and never read * directly. Intercept TSC_AUX instead of exposing it to the -- cgit v1.2.3