Daniel P. Berrangé <berrange@xxxxxxxxxx> writes: > On Wed, May 05, 2021 at 10:22:57AM +0100, Alex Bennée wrote: >> Currently attempts to add a new TCG trace events results in failures >> to build. Previous discussions have suggested maybe it's time to mark >> the feature as deprecated and push people towards using plugins. >> >> Signed-off-by: Alex Bennée <alex.bennee@xxxxxxxxxx> >> Cc: Luis Vilanova <vilanova@xxxxxxxxxxxxxx> >> Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx> >> --- >> docs/devel/tcg-plugins.rst | 2 ++ >> docs/devel/tracing.rst | 7 +++++++ >> docs/system/deprecated.rst | 13 +++++++++++++ >> 3 files changed, 22 insertions(+) >> >> diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst >> index 18c6581d85..edf04e3091 100644 >> --- a/docs/devel/tcg-plugins.rst >> +++ b/docs/devel/tcg-plugins.rst >> @@ -3,6 +3,8 @@ >> Copyright (c) 2019, Linaro Limited >> Written by Emilio Cota and Alex Bennée >> >> +.. _tcgplugin-ref: >> + >> ================ >> QEMU TCG Plugins >> ================ >> diff --git a/docs/devel/tracing.rst b/docs/devel/tracing.rst >> index ba83954899..6b0f46cd54 100644 >> --- a/docs/devel/tracing.rst >> +++ b/docs/devel/tracing.rst >> @@ -414,6 +414,13 @@ disabled, this check will have no performance impact. >> "tcg" >> ----- >> >> +.. warning:: >> + The ability to add new TCG trace points relies on a having a good >> + understanding of the TCG internals. In the meantime TCG plugins >> + have been introduced which solve many of the same problems with >> + more of a focus on analysing guest code. See :ref:`tcgplugin-ref` >> + for more details. >> + >> Guest code generated by TCG can be traced by defining an event with the "tcg" >> event property. Internally, this property generates two events: >> "<eventname>_trans" to trace the event at translation time, and >> diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst >> index 80cae86252..0c9d3c1e1e 100644 >> --- a/docs/system/deprecated.rst >> +++ b/docs/system/deprecated.rst >> @@ -312,6 +312,19 @@ The ``I7200`` guest CPU relies on the nanoMIPS ISA, which is deprecated >> (the ISA has never been upstreamed to a compiler toolchain). Therefore >> this CPU is also deprecated. >> >> +TCG introspection features >> +-------------------------- >> + >> +TCG trace-events (since 6.1) >> +'''''''''''''''''''''''''''' >> + >> +The ability to add new TCG trace points has bit rotted and as the > > When you say this "has bit rotted", just how bad is the situation ? > > Is the TCG tracing still usable at all, or is is fully broken > already ? Well patches 6/7 got it working for generic TCG things. I haven't been able to get the architecture one working but I suspect that is some sort of interaction between the per-arch trace header generation that I haven't quite figured out yet. It's currently broken without the included patches because it's not really being exercised by anything. >> +feature can be replicated with TCG plugins it will be deprecated. If >> +any user is currently using this feature and needs help with >> +converting to using TCG plugins they should contact the qemu-devel >> +mailing list. >> + > > Regards, > Daniel -- Alex Bennée
