Re: trace_FOO_tcg bit-rotted?

["Vilanova, Lluis" <vilanova@imperial.ac.uk>]

El dt. 13 de 04 de 2021 a les 10:25 +0100, en/na Alex Bennée va
escriure:
> Stefan Hajnoczi <stefanha@redhat.com> writes:
> 
> > On Mon, Apr 12, 2021 at 08:06:57PM +0100, Alex Bennée wrote:
> > > 
> > > Stefan Hajnoczi <stefanha@redhat.com> writes:
> > > 
> > > > On Fri, Apr 09, 2021 at 05:29:08PM +0100, Alex Bennée wrote:
> > > > > 
> > > > > Laurent Vivier <laurent@vivier.eu> writes:
> > > > > 
> > > > > > Le 06/04/2021 à 18:00, Alex Bennée a écrit :
> > > > > > > Hi,
> > > > > > > 
> > > > > > > It's been awhile since I last played with this but I
> > > > > > > think we are
> > > > > > > suffering from not having some test cases for tracing
> > > > > > > code
> > > > > > > generation/execution in the tree. I tried adding a simple
> > > > > > > trace point to
> > > > > > > see if I could track ERET calls:
> <snip>
> > > > 
> > > > Lluís: are you happy to deprecate tcg trace events in favor of
> > > > TCG
> > > > plugins?
> <snip>
> > 
> > That said, I haven't used the TCG trace event functionality and
> > maybe
> > I'm missing something obvious that Lluís will point out :).
> 
> I've updated the Cc to what I think is Lluís current email as I was
> getting bounces from the old academic address.

Hi folks, long time no write; thanks for tracking me down :)

I think it'd be great to deprecate TCG tracing in favour of the plugin
interface, pushing some of the burden out of qemu.

I haven't measured the performance of the plugin interface, but AFAIR
TCG trace prints also use TCG helpers, so there should not be a lot of
difference.

As Stefan pointed out, this means plugin writers will have to write
their own TCG tracing code. Hopefully, the plugin API can be extended
to integrate with qemu's logging backend (it seems qemu_plugin_outs
goes somewhere else), and common plugins can be kept on a separate repo
under the qemu umbrella for easier reuse (e.g., to provide the same
functionality as TCG tracing).


Cheers,
Lluis