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[121.44.66.27]) by smtp.gmail.com with ESMTPSA id v3-20020a170902b7c300b001cfc9ad74a3sm3101284plz.15.2023.11.27.17.40.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Nov 2023 17:40:34 -0800 (PST) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 28 Nov 2023 11:40:29 +1000 Message-Id: Subject: Re: [PATCH v2] powerpc: Don't clobber fr0/vs0 during fp|altivec register save From: "Nicholas Piggin" To: "Michael Ellerman" , "Christophe Leroy" , "Timothy Pearson" X-Mailer: aerc 0.15.2 References: <1921539696.48534988.1700407082933.JavaMail.zimbra@raptorengineeringinc.com> <877cmc7ve9.fsf@mail.lhotse> <439072392.48800901.1700498743840.JavaMail.zimbra@raptorengineeringinc.com> <874jhg6lkn.fsf@mail.lhotse> <1294229534.48922001.1700539832331.JavaMail.zimbra@raptorengineeringinc.com> <87leaqjs8x.fsf@mail.lhotse> <1340817182.49635143.1700784119445.JavaMail.zimbra@raptorengineeringinc.com> <1276384468.50536225.1701110354677.JavaMail.zimbra@raptorengineeringinc.com> <89de310e-bb9a-4485-bc8c-3fbefc90e6f6@csgroup.eu> <871qca4rrc.fsf@mail.lhotse> In-Reply-To: <871qca4rrc.fsf@mail.lhotse> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , linuxppc-dev , regressions Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue Nov 28, 2023 at 10:59 AM AEST, Michael Ellerman wrote: > Christophe Leroy writes: > > Le 27/11/2023 =C3=A0 19:39, Timothy Pearson a =C3=A9crit=C2=A0: > >> Just wanted to check back and see if this patch was going to be > >> queued up soon? We're still having to work around / advertise the > >> data destruction issues the underlying bug is causing on e.g. Debian > >> Stable. > > > > Has any agreement been reach on the final solution ? Seeing the many=20 > > discussion on patch v2 I had the feeling that it was not the final solu= tion. > > The actual patch is fine I think. > > The discussion was about improving the explanation of exactly what's > happening in the change log, and whether there is a larger bug causing > FP corruption unrelated to io-uring. One thing I said is maybe we should remove the "register save" concept entirely and always giveup. But that would not be suitable for a minimal fix. I didn't mean it as an alternate fix. Even if we did always giveup in future, this patch still gives a nicer API. There would have to be a noticable performance advantage to not restoring fr0/vs0 after saving before we'd think about changing it back to clobber, since that encourages foot shooting. Thanks, Nick