Re: [PATCH] SVM: do not generate "external interrupt exit" if other exit is pending

[Gleb Natapov <gleb@redhat.com>]

On Sun, Sep 19, 2010 at 07:29:41PM +0200, Joerg Roedel wrote:
> On Sun, Sep 19, 2010 at 06:41:27PM +0200, Gleb Natapov wrote:
> > Nested SVM checks for external interrupt after injecting nested exception.
> > In case there is external interrupt pending the code generates "external
> > interrupt exit" and overwrites previous exit info. If previously injected
> > exception already generated exit it will be lost.
> 
> Right. Have you seen specific mismehavior due to this problem? I am just
> curious how you found this :-)
Yes. Trying to make async page fault work with nested svm :) It was hard
to fix with reproducible test case. I am not dreaming to fix it just by
code review.

> And another question, can you put the reason for this "if(...) return"
> into an comment before the statement? The whole svm-emulation thing is
> complicated enough so that we should document it well in the code :-)
> 
Complicated is understatement. Will add a comment.

> 	Joerg
> 
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > index 43f5558..1a1f86b 100644
> > --- a/arch/x86/kvm/svm.c
> > +++ b/arch/x86/kvm/svm.c
> > @@ -1707,6 +1707,9 @@ static inline bool nested_svm_intr(struct vcpu_svm *svm)
> >  	if (!(svm->vcpu.arch.hflags & HF_HIF_MASK))
> >  		return false;
> >  
> > +	if (svm->nested.exit_required)
> > +		return false;
> > +
> >  	svm->vmcb->control.exit_code   = SVM_EXIT_INTR;
> >  	svm->vmcb->control.exit_info_1 = 0;
> >  	svm->vmcb->control.exit_info_2 = 0;
> > --
> > 			Gleb.

--
			Gleb.