From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Michael Ellerman" <mpe@ellerman.id.au>,
"Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Timothy Pearson" <tpearson@raptorengineering.com>
Cc: "Jens Axboe" <axboe@kernel.dk>,
"regressions" <regressions@lists.linux.dev>,
"linuxppc-dev" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v2] powerpc: Don't clobber fr0/vs0 during fp|altivec register save
Date: Tue, 28 Nov 2023 11:40:29 +1000 [thread overview]
Message-ID: <CXA293HNWDZM.154HY9QTPC3QU@wheely> (raw)
In-Reply-To: <871qca4rrc.fsf@mail.lhotse>
On Tue Nov 28, 2023 at 10:59 AM AEST, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> > Le 27/11/2023 à 19:39, Timothy Pearson a écrit :
> >> 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
WARNING: multiple messages have this Message-ID (diff)
From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Michael Ellerman" <mpe@ellerman.id.au>,
"Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Timothy Pearson" <tpearson@raptorengineering.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
regressions <regressions@lists.linux.dev>
Subject: Re: [PATCH v2] powerpc: Don't clobber fr0/vs0 during fp|altivec register save
Date: Tue, 28 Nov 2023 11:40:29 +1000 [thread overview]
Message-ID: <CXA293HNWDZM.154HY9QTPC3QU@wheely> (raw)
In-Reply-To: <871qca4rrc.fsf@mail.lhotse>
On Tue Nov 28, 2023 at 10:59 AM AEST, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> > Le 27/11/2023 à 19:39, Timothy Pearson a écrit :
> >> 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
next prev parent reply other threads:[~2023-11-28 1:40 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-19 15:18 [PATCH v2] powerpc: Don't clobber fr0/vs0 during fp|altivec register save Timothy Pearson
2023-11-20 7:10 ` Michael Ellerman
2023-11-20 14:32 ` Nicholas Piggin
2023-11-20 16:45 ` Timothy Pearson
2023-11-20 16:45 ` Timothy Pearson
2023-11-20 23:39 ` Michael Ellerman
2023-11-20 23:39 ` Michael Ellerman
2023-11-21 0:27 ` Nicholas Piggin
2023-11-21 0:27 ` Nicholas Piggin
2023-11-21 1:23 ` Timothy Pearson
2023-11-21 1:23 ` Timothy Pearson
2023-11-21 7:56 ` Nicholas Piggin
2023-11-21 7:56 ` Nicholas Piggin
2023-11-21 4:10 ` Timothy Pearson
2023-11-21 4:10 ` Timothy Pearson
2023-11-21 4:26 ` Timothy Pearson
2023-11-21 4:26 ` Timothy Pearson
2023-11-21 7:54 ` Nicholas Piggin
2023-11-21 7:54 ` Nicholas Piggin
2023-11-22 5:01 ` Michael Ellerman
2023-11-22 5:01 ` Michael Ellerman
2023-11-24 0:01 ` Timothy Pearson
2023-11-24 0:01 ` Timothy Pearson
2023-11-27 18:39 ` Timothy Pearson
2023-11-27 18:39 ` Timothy Pearson
2023-11-27 19:58 ` Christophe Leroy
2023-11-27 19:58 ` Christophe Leroy
2023-11-28 0:59 ` Michael Ellerman
2023-11-28 0:59 ` Michael Ellerman
2023-11-28 1:40 ` Nicholas Piggin [this message]
2023-11-28 1:40 ` Nicholas Piggin
2023-11-27 22:53 ` Michael Ellerman
2023-11-27 22:53 ` Michael Ellerman
2023-11-28 12:57 ` Michael Ellerman
2023-11-28 12:57 ` Michael Ellerman
2023-11-30 16:29 ` Timothy Pearson
2023-11-30 16:29 ` Timothy Pearson
2023-11-21 0:18 ` Nicholas Piggin
2023-11-21 0:18 ` Nicholas Piggin
2023-12-02 23:00 ` Michael Ellerman
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