On Sun, Feb 14, 2010 at 06:51:15PM +0100, Jan Kiszka wrote: > From: Jan Kiszka <[email protected]> > > Stolen from Xen: Instead if stepping over IRET, use the interrupt shadow > to inject the NMI on IRET while still deferring its delivery after the > instruction. This has the same limitation as the existing approach: > Exceptions raised by the IRET will trigger an early NMI injection. The > advantages are that we avoid one VM exit and we no longer have to fiddle > with TF which can conflict with other users. > Neat. I have a test case for this. I'll run it today or tomorrow and let you know.
> Signed-off-by: Jan Kiszka <[email protected]> > --- > > Note: untested! > > arch/x86/kvm/svm.c | 40 +++++++++++++--------------------------- > 1 files changed, 13 insertions(+), 27 deletions(-) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > index 52f78dd..f355dc6 100644 > --- a/arch/x86/kvm/svm.c > +++ b/arch/x86/kvm/svm.c > @@ -107,8 +107,6 @@ struct vcpu_svm { > u32 *msrpm; > > struct nested_state nested; > - > - bool nmi_singlestep; > }; > > /* enable NPT for AMD64 and X86 with PAE */ > @@ -1075,9 +1073,6 @@ static void update_db_intercept(struct kvm_vcpu *vcpu) > svm->vmcb->control.intercept_exceptions &= > ~((1 << DB_VECTOR) | (1 << BP_VECTOR)); > > - if (svm->nmi_singlestep) > - svm->vmcb->control.intercept_exceptions |= (1 << DB_VECTOR); > - > if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) { > if (vcpu->guest_debug & > (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) > @@ -1213,20 +1208,11 @@ static int db_interception(struct vcpu_svm *svm) > struct kvm_run *kvm_run = svm->vcpu.run; > > if (!(svm->vcpu.guest_debug & > - (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)) && > - !svm->nmi_singlestep) { > + (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP))) { > kvm_queue_exception(&svm->vcpu, DB_VECTOR); > return 1; > } > > - if (svm->nmi_singlestep) { > - svm->nmi_singlestep = false; > - if (!(svm->vcpu.guest_debug & KVM_GUESTDBG_SINGLESTEP)) > - svm->vmcb->save.rflags &= > - ~(X86_EFLAGS_TF | X86_EFLAGS_RF); > - update_db_intercept(&svm->vcpu); > - } > - > if (svm->vcpu.guest_debug & > (KVM_GUESTDBG_SINGLESTEP | KVM_GUESTDBG_USE_HW_BP)){ > kvm_run->exit_reason = KVM_EXIT_DEBUG; > @@ -2471,6 +2457,17 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu) > { > struct vcpu_svm *svm = to_svm(vcpu); > > + if (svm->vcpu.arch.hflags & HF_IRET_MASK) { > + /* > + * Inject the NMI before IRET completed, but defer delivery > + * by one instruction with the help of the interrupt shadow. > + * Works at least as long as the IRET does not trigger an > + * exception. > + */ > + svm->vcpu.arch.hflags &= ~HF_IRET_MASK; > + svm->vmcb->control.int_state |= SVM_INTERRUPT_SHADOW_MASK; > + } > + > svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI; > vcpu->arch.hflags |= HF_NMI_MASK; > svm->vmcb->control.intercept |= (1UL << INTERCEPT_IRET); > @@ -2576,18 +2573,7 @@ static void enable_irq_window(struct kvm_vcpu *vcpu) > > static void enable_nmi_window(struct kvm_vcpu *vcpu) > { > - struct vcpu_svm *svm = to_svm(vcpu); > - > - if ((svm->vcpu.arch.hflags & (HF_NMI_MASK | HF_IRET_MASK)) > - == HF_NMI_MASK) > - return; /* IRET will cause a vm exit */ > - > - /* Something prevents NMI from been injected. Single step over > - possible problem (IRET or exception injection or interrupt > - shadow) */ > - svm->nmi_singlestep = true; > - svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF); > - update_db_intercept(vcpu); > + /* VM exit on IRET was already armed on injection */ > } > > static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr) > -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
