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Tue, 10 Sep 2024 07:07:42 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Cc: Eduardo Habkost , Zhao Liu , Marcel Apfelbaum , Beraldo Leal , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Alexandre Iooss , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Pierrick Bouvier , Yanan Wang , Peter Maydell , Mahmoud Mandour , Thomas Huth , qemu-arm@nongnu.org, devel@lists.libvirt.org, Jiaxun Yang , Paolo Bonzini , Richard Henderson , Wainer dos Santos Moschetta Subject: [PATCH 11/26] deprecation: don't enable TCG plugins by default on 32 bit hosts Date: Tue, 10 Sep 2024 15:07:18 +0100 Message-Id: <20240910140733.4007719-12-alex.bennee@linaro.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20240910140733.4007719-1-alex.bennee@linaro.org> References: <20240910140733.4007719-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::133; envelope-from=alex.bennee@linaro.org; helo=mail-lf1-x133.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=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1725977463299116600 The existing plugins already liberally use host pointer stuffing for passing user data which will fail when doing 64 bit guests on 32 bit hosts. We should discourage this by officially deprecating support and adding another nail to the 32 bit host coffin. Signed-off-by: Alex Benn=C3=A9e Reviewed-by: Pierrick Bouvier --- v2 - don't manually set based on CPU type, use __SIZEOF_POINTER__ --- docs/about/deprecated.rst | 11 +++++++++++ configure | 21 ++++++++++++++++++++- 2 files changed, 31 insertions(+), 1 deletion(-) diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst index 88f0f03786..f7c7c33d39 100644 --- a/docs/about/deprecated.rst +++ b/docs/about/deprecated.rst @@ -184,6 +184,17 @@ be an effective use of its limited resources, and thus= intends to discontinue it. Since all recent x86 hardware from the past >10 years is capable of the 64-bit x86 extensions, a corresponding 64-bit OS should be used instead. =20 +TCG Plugin support not enabled by default on 32-bit hosts (since 9.2) +''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' + +While it is still possible to enable TCG plugin support for 32-bit +hosts there are a number of potential pitfalls when instrumenting +64-bit guests. The plugin APIs typically pass most addresses as +uint64_t but practices like encoding that address in a host pointer +for passing as user-data will lose data. As most software analysis +benefits from having plenty of host memory it seems reasonable to +encourage users to use 64 bit builds of QEMU for analysis work +whatever targets they are instrumenting. =20 System emulator CPUs -------------------- diff --git a/configure b/configure index 40186d865e..14581c1b9a 100755 --- a/configure +++ b/configure @@ -516,6 +516,25 @@ case "$cpu" in ;; esac =20 +# Now we have our CPU_CFLAGS we can check if we are targeting a 32 or +# 64 bit host. + +check_64bit_host() { +cat > $TMPC <