Messages in this thread Patch in this message | | | From | Paolo Bonzini <> | Subject | Re: [PATCH v5 07/34] KVM: SVM: Add required changes to support intercepts under SEV-ES | Date | Mon, 14 Dec 2020 16:33:38 +0100 |
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On 10/12/20 18:09, Tom Lendacky wrote: > @@ -2797,7 +2838,27 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) > > static int wrmsr_interception(struct vcpu_svm *svm) > { > - return kvm_emulate_wrmsr(&svm->vcpu); > + u32 ecx; > + u64 data; > + > + if (!sev_es_guest(svm->vcpu.kvm)) > + return kvm_emulate_wrmsr(&svm->vcpu); > + > + ecx = kvm_rcx_read(&svm->vcpu); > + data = kvm_read_edx_eax(&svm->vcpu); > + if (kvm_set_msr(&svm->vcpu, ecx, data)) { > + trace_kvm_msr_write_ex(ecx, data); > + ghcb_set_sw_exit_info_1(svm->ghcb, 1); > + ghcb_set_sw_exit_info_2(svm->ghcb, > + X86_TRAP_GP | > + SVM_EVTINJ_TYPE_EXEPT | > + SVM_EVTINJ_VALID); > + return 1; > + } > + > + trace_kvm_msr_write(ecx, data); > + > + return kvm_skip_emulated_instruction(&svm->vcpu); > } > > static int msr_interception(struct vcpu_svm *svm)
This code duplication is ugly, and does not work with userspace MSR filters too.
But we can instead trap the completion of the MSR read/write to use ghcb_set_sw_exit_info_1 instead of kvm_inject_gp, with a callback like
static int svm_complete_emulated_msr(struct kvm_vcpu *vcpu, int err) { if (!sev_es_guest(svm->vcpu.kvm) || !err) return kvm_complete_insn_gp(&svm->vcpu, err);
ghcb_set_sw_exit_info_1(svm->ghcb, 1); ghcb_set_sw_exit_info_2(svm->ghcb, X86_TRAP_GP | SVM_EVTINJ_TYPE_EXEPT | SVM_EVTINJ_VALID); return 1; }
... .complete_emulated_msr = svm_complete_emulated_msr,
> @@ -2827,7 +2888,14 @@ static int interrupt_window_interception(struct vcpu_svm *svm) > static int pause_interception(struct vcpu_svm *svm) > { > struct kvm_vcpu *vcpu = &svm->vcpu; > - bool in_kernel = (svm_get_cpl(vcpu) == 0); > + bool in_kernel; > + > + /* > + * CPL is not made available for an SEV-ES guest, so just set in_kernel > + * to true. > + */ > + in_kernel = (sev_es_guest(svm->vcpu.kvm)) ? true > + : (svm_get_cpl(vcpu) == 0); > > if (!kvm_pause_in_guest(vcpu->kvm)) > grow_ple_window(vcpu);
See below.
> @@ -3273,6 +3351,13 @@ bool svm_interrupt_blocked(struct kvm_vcpu *vcpu) > struct vcpu_svm *svm = to_svm(vcpu); > struct vmcb *vmcb = svm->vmcb; > > + /* > + * SEV-ES guests to not expose RFLAGS. Use the VMCB interrupt mask > + * bit to determine the state of the IF flag. > + */ > + if (sev_es_guest(svm->vcpu.kvm)) > + return !(vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK);
This seems wrong, you have to take into account SVM_INTERRUPT_SHADOW_MASK as well. Also, even though GIF is not really used by SEV-ES guests, I think it's nicer to put this check afterwards.
That is:
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 4372e45c8f06..2dd9c9698480 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3247,7 +3247,14 @@ bool svm_interrupt_blocked(struct kvm_vcpu *vcpu) if (!gif_set(svm)) return true;
- if (is_guest_mode(vcpu)) { + if (sev_es_guest(svm->vcpu.kvm)) { + /* + * SEV-ES guests to not expose RFLAGS. Use the VMCB interrupt mask + * bit to determine the state of the IF flag. + */ + if (!(vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK)) + return true; + } else if (is_guest_mode(vcpu)) { /* As long as interrupts are being delivered... */ if ((svm->nested.ctl.int_ctl & V_INTR_MASKING_MASK) ? !(svm->nested.hsave->save.rflags & X86_EFLAGS_IF)
> if (!gif_set(svm)) > return true; > > @@ -3458,6 +3543,12 @@ static void svm_complete_interrupts(struct vcpu_svm *svm) > svm->vcpu.arch.nmi_injected = true; > break; > case SVM_EXITINTINFO_TYPE_EXEPT: > + /* > + * Never re-inject a #VC exception. > + */ > + if (vector == X86_TRAP_VC) > + break; > + > /* > * In case of software exceptions, do not reinject the vector, > * but re-execute the instruction instead. Rewind RIP first > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index a3fdc16cfd6f..b6809a2851d2 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -4018,7 +4018,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) > { > int idx; > > - if (vcpu->preempted) > + if (vcpu->preempted && !vcpu->arch.guest_state_protected) > vcpu->arch.preempted_in_kernel = !kvm_x86_ops.get_cpl(vcpu);
This has to be true, otherwise no directed yield will be done at all:
if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode && !kvm_arch_vcpu_in_kernel(vcpu)) continue; Or more easily, just use in_kernel == false in pause_interception, like
+ /* + * CPL is not made available for an SEV-ES guest, therefore + * vcpu->arch.preempted_in_kernel can never be true. Just + * set in_kernel to false as well. + */ + in_kernel = !sev_es_guest(svm->vcpu.kvm) && svm_get_cpl(vcpu) == 0; > > /* > @@ -8161,7 +8161,9 @@ static void post_kvm_run_save(struct kvm_vcpu *vcpu) > { > struct kvm_run *kvm_run = vcpu->run; > > - kvm_run->if_flag = (kvm_get_rflags(vcpu) & X86_EFLAGS_IF) != 0; > + kvm_run->if_flag = (vcpu->arch.guest_state_protected) > + ? kvm_arch_interrupt_allowed(vcpu) > + : (kvm_get_rflags(vcpu) & X86_EFLAGS_IF) != 0;
Here indeed you only want the interrupt allowed bit, not the interrupt window. But we can just be bold and always set it to true.
- for userspace irqchip, kvm_run->ready_for_interrupt_injection is set just below and it will always be false if kvm_arch_interrupt_allowed is false
- for in-kernel APIC, if_flag is documented to be invalid (though it actually is valid). For split irqchip, they can just use kvm_run->ready_for_interrupt_injection; for entirely in-kernel interrupt handling, userspace does not need if_flag at all.
Paolo
> kvm_run->flags = is_smm(vcpu) ? KVM_RUN_X86_SMM : 0; > kvm_run->cr8 = kvm_get_cr8(vcpu); > kvm_run->apic_base = kvm_get_apic_base(vcpu); >
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