Re: [PATCH v2] powerpc: Don't clobber fr0/vs0 during fp|altivec register save
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2023-11-28 01:41:29
Also in:
regressions
From: "Nicholas Piggin" <npiggin@gmail.com>
Date: 2023-11-28 01:41:29
Also in:
regressions
On Tue Nov 28, 2023 at 10:59 AM AEST, Michael Ellerman wrote:
Christophe Leroy [off-list ref] writes:quoted
Le 27/11/2023 à 19:39, Timothy Pearson a écrit :quoted
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 discussion on patch v2 I had the feeling that it was not the final solution.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