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[109.42.50.234]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5dc186d8a27sm8013842a12.73.2025.01.28.22.23.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jan 2025 22:23:49 -0800 (PST) Message-ID: Date: Wed, 29 Jan 2025 07:23:47 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/1] meson: Deprecate 32-bit host systems To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , =?UTF-8?Q?Daniel_P=2E_Berrang=C3=A9?= Cc: =?UTF-8?Q?Alex_Benn=C3=A9e?= , Richard Henderson , qemu-devel@nongnu.org, peter.maydell@linaro.org, stefanha@redhat.com, pbonzini@redhat.com, mark.cave-ayland@ilande.co.uk, Liviu Ionescu References: <20250128004254.33442-1-richard.henderson@linaro.org> <9a280789-9248-4eca-b50c-048fc58e3f53@redhat.com> <87plk72tvr.fsf@draig.linaro.org> <8c0eea44-d0bf-4b86-9b1b-1c2082ab2df9@linaro.org> <9bf6d4b0-7a89-4110-a1e1-46bbdb2fc793@linaro.org> From: Thomas Huth Content-Language: en-US Autocrypt: addr=thuth@redhat.com; keydata= xsFNBFH7eUwBEACzyOXKU+5Pcs6wNpKzrlJwzRl3VGZt95VCdb+FgoU9g11m7FWcOafrVRwU yYkTm9+7zBUc0sW5AuPGR/dp3pSLX/yFWsA/UB4nJsHqgDvDU7BImSeiTrnpMOTXb7Arw2a2 4CflIyFqjCpfDM4MuTmzTjXq4Uov1giGE9X6viNo1pxyEpd7PanlKNnf4PqEQp06X4IgUacW tSGj6Gcns1bCuHV8OPWLkf4hkRnu8hdL6i60Yxz4E6TqlrpxsfYwLXgEeswPHOA6Mn4Cso9O 0lewVYfFfsmokfAVMKWzOl1Sr0KGI5T9CpmRfAiSHpthhHWnECcJFwl72NTi6kUcUzG4se81 O6n9d/kTj7pzTmBdfwuOZ0YUSqcqs0W+l1NcASSYZQaDoD3/SLk+nqVeCBB4OnYOGhgmIHNW 0CwMRO/GK+20alxzk//V9GmIM2ACElbfF8+Uug3pqiHkVnKqM7W9/S1NH2qmxB6zMiJUHlTH gnVeZX0dgH27mzstcF786uPcdEqS0KJuxh2kk5IvUSL3Qn3ZgmgdxBMyCPciD/1cb7/Ahazr 3ThHQXSHXkH/aDXdfLsKVuwDzHLVSkdSnZdt5HHh75/NFHxwaTlydgfHmFFwodK8y/TjyiGZ zg2Kje38xnz8zKn9iesFBCcONXS7txENTzX0z80WKBhK+XSFJwARAQABzR5UaG9tYXMgSHV0 aCA8dGh1dGhAcmVkaGF0LmNvbT7CwXgEEwECACIFAlVgX6oCGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAAoJEC7Z13T+cC21EbIP/ii9cvT2HHGbFRl8HqGT6+7Wkb+XLMqJBMAIGiQK QIP3xk1HPTsLfVG0ao4hy/oYkGNOP8+ubLnZen6Yq3zAFiMhQ44lvgigDYJo3Ve59gfe99KX EbtB+X95ODARkq0McR6OAsPNJ7gpEUzfkQUUJTXRDQXfG/FX303Gvk+YU0spm2tsIKPl6AmV 1CegDljzjycyfJbk418MQmMu2T82kjrkEofUO2a24ed3VGC0/Uz//XCR2ZTo+vBoBUQl41BD eFFtoCSrzo3yPFS+w5fkH9NT8ChdpSlbNS32NhYQhJtr9zjWyFRf0Zk+T/1P7ECn6gTEkp5k ofFIA4MFBc/fXbaDRtBmPB0N9pqTFApIUI4vuFPPO0JDrII9dLwZ6lO9EKiwuVlvr1wwzsgq zJTPBU3qHaUO4d/8G+gD7AL/6T4zi8Jo/GmjBsnYaTzbm94lf0CjXjsOX3seMhaE6WAZOQQG tZHAO1kAPWpaxne+wtgMKthyPLNwelLf+xzGvrIKvLX6QuLoWMnWldu22z2ICVnLQChlR9d6 WW8QFEpo/FK7omuS8KvvopFcOOdlbFMM8Y/8vBgVMSsK6fsYUhruny/PahprPbYGiNIhKqz7 UvgyZVl4pBFjTaz/SbimTk210vIlkDyy1WuS8Zsn0htv4+jQPgo9rqFE4mipJjy/iboDzsFN BFH7eUwBEAC2nzfUeeI8dv0C4qrfCPze6NkryUflEut9WwHhfXCLjtvCjnoGqFelH/PE9NF4 4VPSCdvD1SSmFVzu6T9qWdcwMSaC+e7G/z0/AhBfqTeosAF5XvKQlAb9ZPkdDr7YN0a1XDfa +NgA+JZB4ROyBZFFAwNHT+HCnyzy0v9Sh3BgJJwfpXHH2l3LfncvV8rgFv0bvdr70U+On2XH 5bApOyW1WpIG5KPJlDdzcQTyptOJ1dnEHfwnABEfzI3dNf63rlxsGouX/NFRRRNqkdClQR3K gCwciaXfZ7ir7fF0u1N2UuLsWA8Ei1JrNypk+MRxhbvdQC4tyZCZ8mVDk+QOK6pyK2f4rMf/ WmqxNTtAVmNuZIwnJdjRMMSs4W4w6N/bRvpqtykSqx7VXcgqtv6eqoDZrNuhGbekQA0sAnCJ VPArerAZGArm63o39me/bRUQeQVSxEBmg66yshF9HkcUPGVeC4B0TPwz+HFcVhheo6hoJjLq knFOPLRj+0h+ZL+D0GenyqD3CyuyeTT5dGcNU9qT74bdSr20k/CklvI7S9yoQje8BeQAHtdV cvO8XCLrpGuw9SgOS7OP5oI26a0548M4KldAY+kqX6XVphEw3/6U1KTf7WxW5zYLTtadjISB X9xsRWSU+Yqs3C7oN5TIPSoj9tXMoxZkCIHWvnqGwZ7JhwARAQABwsFfBBgBAgAJBQJR+3lM AhsMAAoJEC7Z13T+cC21hPAQAIsBL9MdGpdEpvXs9CYrBkd6tS9mbaSWj6XBDfA1AEdQkBOn ZH1Qt7HJesk+qNSnLv6+jP4VwqK5AFMrKJ6IjE7jqgzGxtcZnvSjeDGPF1h2CKZQPpTw890k fy18AvgFHkVk2Oylyexw3aOBsXg6ukN44vIFqPoc+YSU0+0QIdYJp/XFsgWxnFIMYwDpxSHS 5fdDxUjsk3UBHZx+IhFjs2siVZi5wnHIqM7eK9abr2cK2weInTBwXwqVWjsXZ4tq5+jQrwDK cvxIcwXdUTLGxc4/Z/VRH1PZSvfQxdxMGmNTGaXVNfdFZjm4fz0mz+OUi6AHC4CZpwnsliGV ODqwX8Y1zic9viSTbKS01ZNp175POyWViUk9qisPZB7ypfSIVSEULrL347qY/hm9ahhqmn17 Ng255syASv3ehvX7iwWDfzXbA0/TVaqwa1YIkec+/8miicV0zMP9siRcYQkyTqSzaTFBBmqD oiT+z+/E59qj/EKfyce3sbC9XLjXv3mHMrq1tKX4G7IJGnS989E/fg6crv6NHae9Ckm7+lSs IQu4bBP2GxiRQ+NV3iV/KU3ebMRzqIC//DCOxzQNFNJAKldPe/bKZMCxEqtVoRkuJtNdp/5a yXFZ6TfE1hGKrDBYAm4vrnZ4CXFSBDllL59cFFOJCkn4Xboj/aVxxJxF30bn In-Reply-To: <9bf6d4b0-7a89-4110-a1e1-46bbdb2fc793@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.3, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, 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 On 28/01/2025 11.02, Philippe Mathieu-Daudé wrote: > On 28/1/25 11:01, Philippe Mathieu-Daudé wrote: >> On 28/1/25 10:27, Daniel P. Berrangé wrote: >>> On Tue, Jan 28, 2025 at 10:17:33AM +0100, Philippe Mathieu-Daudé wrote: >>>> On 28/1/25 10:02, Alex Bennée wrote: >>>>> 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@redhat.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? >>>> >>>> Current maintainers don't have spare time to support the 32-on-32 >>>> emulation. If there is interest in the community for such niche, >>>> someone needs to step forward, willing to maintain it. >>> >>> I'm not sure that's the case here. >>> >>> 32-on-32 is already effectively unmaintained, so we're not suffering >>> in terms of keeping the 32-on-32 code reliable. >>> >>> We're suffering from the complexity that 32-on-32 code places on the >>> rest of the XX-on-64 code that we do care about. >>> >>> IOW if someone volunteered to maintain 32-on-32 that's not actually >>> solving the complexity problem, just perpetuating it. >>> >>> The current maintainers only interested in XX-on-64 will still suffer >>> ongoing burden from the code complexity caused by 32-on-32 merely >>> existing. >>> >>> So again lets be clear... >>> >>> Either we... >>> >>>   * ...want to kill 32-on-32 code to reduce the complexity on the >>>     main XX-on-64 codebase regardless of interest in 32-on-32 >>> >>> Or >>> >>>   * ...want to kill 32-on-32 code because it is buggy due to lack >>>     of maintainers, but would welcome someone to step forward to >>>     maintain it >>> >>> It sounded like we were wanting the former, not the latter. >> >> Yes, we want to former. But as Thomas pointed out, last time >> someone showed up, and while the maintainers weren't willing to >> keep 32-on-32 [*], they kept maintaining it at the price of restricting >> XX-on-64. >> >> [*] back then we proved system emulation XX-on-32 wasn't really useful >> anymore, and user emulation 64-on-32 was partly broken, so only >> 32-on-32 user emulation was functional. > > So it seems reasonable to deprecate and ask interested 32-on-32 user > emulation users to use QEMU 10.1 release. So unless someone complains immediately with a good reason, I'm also in favor of marking it as deprecated now. If then someone complains during the deprecation period, we still can reconsider and remove the deprecation note again. Thus for this patch from my side: Reviewed-by: Thomas Huth