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Tue, 28 Jan 2025 01:02:49 -0800 (PST) Received: from draig.lan ([85.9.250.243]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab6760fbf38sm742420666b.143.2025.01.28.01.02.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jan 2025 01:02:49 -0800 (PST) Received: from draig (localhost [IPv6:::1]) by draig.lan (Postfix) with ESMTP id 719AF5F8D1; Tue, 28 Jan 2025 09:02:48 +0000 (GMT) From: =?utf-8?Q?Alex_Benn=C3=A9e?= To: Thomas Huth Cc: Richard Henderson , qemu-devel@nongnu.org, peter.maydell@linaro.org, stefanha@redhat.com, pbonzini@redhat.com, berrange@redhat.com, philmd@linaro.org, mark.cave-ayland@ilande.co.uk, Liviu Ionescu Subject: Re: [PATCH 0/1] meson: Deprecate 32-bit host systems In-Reply-To: <9a280789-9248-4eca-b50c-048fc58e3f53@redhat.com> (Thomas Huth's message of "Tue, 28 Jan 2025 05:00:35 +0100") References: <20250128004254.33442-1-richard.henderson@linaro.org> <9a280789-9248-4eca-b50c-048fc58e3f53@redhat.com> User-Agent: mu4e 1.12.8; emacs 29.4 Date: Tue, 28 Jan 2025 09:02:48 +0000 Message-ID: <87plk72tvr.fsf@draig.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::629; envelope-from=alex.bennee@linaro.org; helo=mail-ej1-x629.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, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Thomas Huth writes: > On 28/01/2025 01.42, Richard Henderson wrote: >> Time for our biennial attempt to kill ancient hosts. >> I've been re-working the tcg code generator a bit over the holidays. >> One place that screams for a bit of cleanup is with 64-bit guest >> addresses on 32-bit hosts. Of course the best "cleanup" is to not >> have to handle such silliness at all. >> Two years after Thomas' last attempt, >> https://lore.kernel.org/qemu-devel/20230130114428.1297295-1-thuth@red= hat.com/ >> which resulted only in deprecation of i686 host for system >> emulation. >> By itself, this just isn't enough for large-scale cleanups. >> I'll note that we've separately deprecated mips32, set to expire >> with the end of Debian bookworm, set to enter LTS in June 2026. >> I'll note that there is *already* no Debian support for ppc32, >> and that I am currently unable to cross-compile that host at all. > > IIRC the biggest pushback that I got two years ago was with regards to > 32-bit arm: The recommended version of Raspberry Pi OS is still > 32-bit: > > https://lore.kernel.org/qemu-devel/F852C238-77B8-4E24-9494-8D060EB78F9F@= livius.net/ > > And looking at https://www.raspberrypi.com/software/operating-systems/ > this still seems to be the case... > > So I guess the main question is now: Would it be ok to kill support > for 32-bit Raspberry Pi OS nowadays? I would argue yes for a few reasons. - you can't buy 32 bit only Pi's AFAICT, even the Pi Zero 2W can work with a 64 bit OS. - It's not like the versions shipping in bullseye and bookworm will stop working. - Even if we deprecate now there will likely be one more Debian release cycle that gets 32 bit host support. >> Showing my hand a bit, I am willing to limit deprecation to >> 64-bit guests on 32-bit hosts. But I'd prefer to go the whole hog: >> unconditional support for TCG_TYPE_I64 would remove a *lot* of >> 32-bit fallback code. I support going the whole hog. I would be curious what use cases still exist for an up to date 32-on-32 QEMU based emulation?=20 > > Sound like a good alternative to me! > > Thomas --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro