Re: [Qemu-devel] GSoC mentor summit QEMU users session

[Lluís Vilanova]

Stefan Hajnoczi writes:

> On Thu, Nov 03, 2011 at 10:35:28AM +0100, Fabien Chouteau wrote:
>> On 03/11/2011 08:44, Stefan Hajnoczi wrote:
>> > On Wed, Nov 2, 2011 at 5:39 PM, Fabien Chouteau <address@hidden> wrote:
>> >> On 29/10/2011 15:52, Alexander Graf wrote:
>> > I took a quick peak at the qemu-trace.[ch] from couverture and it
>> > looks along the lines of the instrumentation that others have been
>> > doing too.  I hope you have time to propose the coverage
>> > instrumentation for upstream QEMU.
>> >
>> 
>> I don't know much about other instrumentations in Qemu (pointers are
>> welcome :), but what we have in couverture-qemu is not trivial,
>> especially when it comes to MC/DC analysis. You should take a look at
>> 201005-erts2.pdf if you want technical details.

> My impression was that the QEMU portion of instrumentation was fairly
> simple - it writes out trace records at various interesting points
> during guest execution in TCG.

> I think fancy analysis scripts do not have to be part of QEMU but they
> could be added to scripts/ or put in a new contrib/ directory.

I've only had a brief look into the changes, but I think the mechanism I
implemented has a cleaner fit into QEMU, thanks to previous feedback from this
list.

It explicitly separates the tracing mechanism (in QEMU itself) from the specific
trace analysis (which resides in a separate library specified by the user at
compile time, where most of couverture would go).

On the other hand, I have a complementary set of events, so we can definitely
join the efforts on that side (e.g., I haven't yet went into the trouble of
adding the begin/end TB or branch events).

I have only managed to send the most general changes that are needed before
having the full-fledged instrumentation, but if there's no opposition on having
this kind of feature I will start sending the rest once mainline opens up again
(which I believe won't take much more time).


Lluis

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