Re: [PATCH 22/24] Correct handling of idt vectoring info

[Avi Kivity <avi@redhat.com>]

  On 09/23/2010 01:15 AM, Nadav Har'El wrote:
> On Mon, Sep 20, 2010, Avi Kivity wrote about "Re: [PATCH 22/24] Correct handling of idt vectoring info":
> >  >I'm afraid I know very little about the SVM architecture. Does SVM even
> >  >have
> >  >a parallel of the IDT_VECTORING_INFO that this patch is trying to address?
> >
> >  It does. exit_int_info.
>
> Thanks. I guess I need to do some serious reading on this subject. I guessed
> that exit_int_info was more of a parallel of VMX's vm_exit_intr_info field and
> not idt_vectoring_info, but I guess I was wrong.

svm has separate intercepts for every exception, so it doesn't need the 
vector field of vm_exit_intr_info_field.  The error code is stored in 
exit_info_1, cr2 (for #PF) in exit_info_2.

> >  >I agree that the nested SVM's handle_exit() looks cleaner that the parallel
> >  >code in nested VMX. The root of all evil is that second exit decision point
> >  >in the injection phase, and I'll think some more if I can find a way to
> >  >avoid it without rocking the foundations too much.
> >  >
> >
> >  I think svm needs it too.
>
> Can you please clarify? I didn't understand what "it" refers to here.
>
>

Sorry, it was a week ago.

In general I think both svm and vmx need to go through the 
exception/interrupt queues.  That is, if you exit with 
IDT_VECTORING_INFO_VALID, you unpack it into the queue as a pending 
exception, and when you enter again you load it into 
VM_ENTRY_INTR_INFO_FIELD.  That's a bit of work, but it reduces the 
amount of code paths when L0 needs to inject an exception into L2 (like 
in emulation) - all it has to do is to queue it into the generic 
exception queue.

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