Re: [kvm-devel] [RFC][PATCH 2/4] kvm: Arch-specifc KVM_EXIT_DEBUG payload

[Jan Kiszka <jan.kiszka@web.de>]

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Avi Kivity wrote:
> Jan Kiszka wrote:
>>
>>> We need to handle branch tracing and last branch recording as well.  It
>>> doesn't have to be in this patchset, though.
>>>     
>>
>> IIRC, both features are fairly vendor specific. Do we have the same
>> level of support on both AMD and Intel CPUs? Moreover, I doubt that the
>> debug interface would be the right place for them.
>>   
> 
> Branch tracing is common, and is very much related to debugging (it
> modifies singlestep to trap only on branches, not on non-branching
> insns).  LBR is either common or very similar, and is also very
> important for debugging.

Well, might be useful. But then we would also have to teach this support
to the gdb remote protocol and the gdb frontend, because neither of both
seems to make use of it yet. And do other archs have it as well? If at
all, I guess the way this is realized there varies a lot, and thus
abstracting it is the real problem.

However, we can keep it in mind for the time the basic feature set works
perfectly. :)

Jan


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