From: Dave Martin <Dave.Martin@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
Suzuki Poulose <Suzuki.Poulose@arm.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"will@kernel.org" <will@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/3] arm64: cpufeature: Fix the type of no FP/SIMD capability
Date: Tue, 15 Oct 2019 15:05:42 +0100 [thread overview]
Message-ID: <20191015140541.GW27757@arm.com> (raw)
In-Reply-To: <CAKv+Gu_=jw94Hj5Vo=5w+hb5RcPR4SQvxOM02WQr9hDhyzE67g@mail.gmail.com>
On Tue, Oct 15, 2019 at 12:30:15PM +0200, Ard Biesheuvel wrote:
> On Tue, 15 Oct 2019 at 12:25, Dave Martin <Dave.Martin@arm.com> wrote:
> >
> > On Mon, Oct 14, 2019 at 06:57:30PM +0200, Ard Biesheuvel wrote:
[...]
> > > All in-kernel NEON code checks whether the NEON is usable, so I'd
> > > expect that check to return 'false' if it is too early in the boot for
> > > the NEON to be used at all.
> >
> > My concern is that the check may be done once, at probe time, for crypto
> > drivers. If probing happens before system_supports_fpsimd() has
> > stabilised, we may be stuck with the wrong probe decision.
> >
> > So: are crypto drivers and kernel_mode_neon() users definitely only
> > probed _after_ all early CPUs are up?
> >
>
> Isn't SMP already up when initcalls are processed?
That was my original assumption when developing SVE. I think I
convinced myself that it was valid, but it sounds worth reinvestigating.
Assuming the assumption _is_ valid, then dropping a suitable WARN() into
system_supports_fpsimd() or cpu_has_neon() or similar may be a good idea.
Cheers
---Dave
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-10-15 14:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 17:15 [PATCH 0/3] arm64: Fix support for systems without FP/SIMD Suzuki K Poulose
2019-10-10 17:15 ` [PATCH 1/3] arm64: cpufeature: Fix the type of no FP/SIMD capability Suzuki K Poulose
2019-10-11 11:36 ` Dave Martin
2019-10-11 12:13 ` Suzuki K Poulose
2019-10-11 14:21 ` Dave Martin
2019-10-11 17:28 ` Suzuki K Poulose
2019-10-14 14:52 ` Dave Martin
2019-10-14 15:45 ` Suzuki K Poulose
2019-10-14 15:50 ` Dave P Martin
2019-10-14 16:57 ` Ard Biesheuvel
2019-10-15 9:44 ` Suzuki K Poulose
2019-10-15 9:52 ` Ard Biesheuvel
2019-10-15 10:24 ` Dave Martin
2019-10-15 10:30 ` Ard Biesheuvel
2019-10-15 13:03 ` Suzuki K Poulose
2019-10-15 13:11 ` Ard Biesheuvel
2019-10-15 14:05 ` Dave Martin [this message]
2019-10-10 17:15 ` [PATCH 2/3] arm64: nofpsmid: Clear TIF_FOREIGN_FPSTATE flag for early tasks Suzuki K Poulose
2019-10-11 11:26 ` Dave Martin
2019-10-17 12:42 ` Suzuki K Poulose
2019-10-17 16:09 ` Dave Martin
2019-10-10 17:15 ` [PATCH 3/3] arm64: cpufeature: Set the FP/SIMD compat HWCAP bits properly Suzuki K Poulose
2019-10-17 0:06 ` [PATCH 0/3] arm64: Fix support for systems without FP/SIMD Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191015140541.GW27757@arm.com \
--to=dave.martin@arm.com \
--cc=Catalin.Marinas@arm.com \
--cc=Mark.Rutland@arm.com \
--cc=Suzuki.Poulose@arm.com \
--cc=ard.biesheuvel@linaro.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).