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Wed, 05 May 2021 03:37:36 -0700 (PDT) Received: from zen.linaroharston ([51.148.130.216]) by smtp.gmail.com with ESMTPSA id s6sm5357097wms.0.2021.05.05.03.37.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 May 2021 03:37:35 -0700 (PDT) Received: from zen (localhost [127.0.0.1]) by zen.linaroharston (Postfix) with ESMTP id 0F1D11FF7E; Wed, 5 May 2021 11:37:34 +0100 (BST) References: <20210505092259.8202-1-alex.bennee@linaro.org> <20210505092259.8202-6-alex.bennee@linaro.org> User-agent: mu4e 1.5.13; emacs 28.0.50 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: =?utf-8?Q?Daniel_P=2E_Berrang=C3=A9?= Subject: Re: [PATCH v1 5/7] docs: mark intention to deprecate TCG tracing functionality Date: Wed, 05 May 2021 11:35:16 +0100 In-reply-to: Message-ID: <87lf8to49d.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::42c; envelope-from=alex.bennee@linaro.org; helo=mail-wr1-x42c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "reviewer:Incompatible changes" , qemu-devel@nongnu.org, robhenry@microsoft.com, aaron@os.amperecomputing.com, vilanova@imperial.ac.uk, mahmoudabdalghany@outlook.com, minyihh@uci.edu, cota@braap.org, stefanha@redhat.com, mohamad.gebai@gmail.com, kuhn.chenqun@huawei.com, matheus.ferst@eldorado.org.br Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > On Wed, May 05, 2021 at 10:22:57AM +0100, Alex Benn=C3=A9e 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. >>=20 >> Signed-off-by: Alex Benn=C3=A9e >> Cc: Luis Vilanova >> Cc: Stefan Hajnoczi >> --- >> docs/devel/tcg-plugins.rst | 2 ++ >> docs/devel/tracing.rst | 7 +++++++ >> docs/system/deprecated.rst | 13 +++++++++++++ >> 3 files changed, 22 insertions(+) >>=20 >> 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 Benn=C3=A9e >>=20=20 >> +.. _tcgplugin-ref: >> + >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >> QEMU TCG Plugins >> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >> 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 impac= t. >> "tcg" >> ----- >>=20=20 >> +.. 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: >> "_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. >>=20=20 >> +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 --=20 Alex Benn=C3=A9e