diff options
Diffstat (limited to 'arch/x86/kvm/svm/svm.c')
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a713c803a3a3..e67de787fc71 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3165,6 +3165,27 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) kvm_pr_unimpl_wrmsr(vcpu, ecx, data); break; } + + /* + * AMD changed the architectural behavior of bits 5:2. On CPUs + * without BusLockTrap, bits 5:2 control "external pins", but + * on CPUs that support BusLockDetect, bit 2 enables BusLockTrap + * and bits 5:3 are reserved-to-zero. Sadly, old KVM allowed + * the guest to set bits 5:2 despite not actually virtualizing + * Performance-Monitoring/Breakpoint external pins. Drop bits + * 5:2 for backwards compatibility. + */ + data &= ~GENMASK(5, 2); + + /* + * Suppress BTF as KVM doesn't virtualize BTF, but there's no + * way to communicate lack of support to the guest. + */ + if (data & DEBUGCTLMSR_BTF) { + kvm_pr_unimpl_wrmsr(vcpu, MSR_IA32_DEBUGCTLMSR, data); + data &= ~DEBUGCTLMSR_BTF; + } + if (data & DEBUGCTL_RESERVED_BITS) return 1; @@ -4189,6 +4210,18 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + /* + * Set RFLAGS.IF prior to VMRUN, as the host's RFLAGS.IF at the time of + * VMRUN controls whether or not physical IRQs are masked (KVM always + * runs with V_INTR_MASKING_MASK). Toggle RFLAGS.IF here to avoid the + * temptation to do STI+VMRUN+CLI, as AMD CPUs bleed the STI shadow + * into guest state if delivery of an event during VMRUN triggers a + * #VMEXIT, and the guest_state transitions already tell lockdep that + * IRQs are being enabled/disabled. Note! GIF=0 for the entirety of + * this path, so IRQs aren't actually unmasked while running host code. + */ + raw_local_irq_enable(); + amd_clear_divider(); if (sev_es_guest(vcpu->kvm)) @@ -4197,6 +4230,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in else __svm_vcpu_run(svm, spec_ctrl_intercepted); + raw_local_irq_disable(); + guest_state_exit_irqoff(); } @@ -4253,6 +4288,16 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, clgi(); kvm_load_guest_xsave_state(vcpu); + /* + * Hardware only context switches DEBUGCTL if LBR virtualization is + * enabled. Manually load DEBUGCTL if necessary (and restore it after + * VM-Exit), as running with the host's DEBUGCTL can negatively affect + * guest state and can even be fatal, e.g. due to Bus Lock Detect. + */ + if (!(svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK) && + vcpu->arch.host_debugctl != svm->vmcb->save.dbgctl) + update_debugctlmsr(svm->vmcb->save.dbgctl); + kvm_wait_lapic_expire(vcpu); /* @@ -4280,6 +4325,10 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, if (unlikely(svm->vmcb->control.exit_code == SVM_EXIT_NMI)) kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); + if (!(svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK) && + vcpu->arch.host_debugctl != svm->vmcb->save.dbgctl) + update_debugctlmsr(vcpu->arch.host_debugctl); + kvm_load_host_xsave_state(vcpu); stgi(); |