Re: [PATCH] KVM: VMX: Update instruction length on intercepted BP

Gleb Natapov
2010-02-17T11:13:37Z

On Wed, Feb 17, 2010 at 01:11:36PM +0200, Avi Kivity wrote:
> On 02/15/2010 03:30 PM, Gleb Natapov wrote:
> >
> >>I just did this on our primary AMD platform (Embedded Opteron, 13KS EE),
> >>and it just worked.
> >>
> >>But this is a fairly new processor. Consequently, it reports NextRIP
> >>support via cpuid function 0x8000000A. Looking for an older one too.
> >>
> >>In the meantime I also browsed a bit more in the manuals, and I don't
> >>think stepping over or (what is actually required) into an INT3 will
> >>work. We can't step into as the processor clears TF on any event handler
> >>entry. And stepping over would cause troubles
> >>
> >>a) as an unknown amount of code may run without #DB interception
> >>b) we would fiddle with TF in code that is already under debugger
> >> control, thus we would very likely run into conflicts.
> >>
> >>Leaves us with tricky INT3 emulation. Sigh.
> >>
> >So the question is do we want to support this kind of debugging on older
> >AMDs. May we don't.
>
> How much older are they?
>
Actually I am not sure new AMDs support this correctly. Need one to run
tests. GDB is not a good test case, it is too smart.

--
Gleb.