On Tue, May 05, 2009 at 10:45:20AM +0200, Jan Kiszka wrote:
> > @@ -2331,8 +2358,16 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
> > {
> > struct vcpu_svm *svm = to_svm(vcpu);
> >
> > - if (svm->vmcb->control.int_state & SVM_INTERRUPT_SHADOW_MASK)
> > - enable_irq_window(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) */
> > + vcpu->arch.singlestep = true;
> > + svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
>
> Can you single-step like this out of an IRQ handler? I mean, IRET will
> restore the flags from the stack, and those settings should be
> overwritten. Or am I missing something?
>
It seems to be working :) Shouldn't CPU checks single step before
executing IRET and thus using old flags value? It is interesting to
check what rflag value is immediately after IRET.
--
Gleb.
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