Re: [Qemu-devel] [PATCH 00/12] trace: [tcg] Allow tracing guest events in TCG-generated code

[Lluís Vilanova]

Stefan Hajnoczi writes:

> On Fri, Jan 31, 2014 at 05:09:03PM +0100, Lluís Vilanova wrote:
>> Adds the base ability to specify which events in the "trace-events" file may 
>> be
>> used to trace guest activity in the TCG code (using the "tcg" event propery).
>> 
>> Such events generate an extra set of tracing functions that can be called 
>> during
>> TCG code generation and will automatically redirect a call to the appropriate
>> backend-dependent tracing functions when the guest code is executed.

> I've never worked on TCG but this seems like a good idea: a way to plant
> trace events in TCG-generated code.

> CCing TCG folks to check they are happy with the approach

> Once any high-level discussion is done I'll review the tracing changes.

I have some other guest code events on other patches (e.g., instruction/BBL
execution), but memory accesses are useful and simple enough to show how it
works.

Another question is whether the tracing functions called during translation
(trace_${name}_tcg) should also be themselves traceable (e.g., to see in a trace
how many times and which instructions are translated by QEMU).


Thanks,
  Lluis

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