linux-kernel - Re: [PATCH] kselftest/arm64: abi: fix SVCR detection

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Message-ID: <CAHk0HotQ-=s+-FHh8pAOg10ivcRwqChG735qgDvuQd=4B1QQNA@mail.gmail.com>
Date: Mon, 9 Dec 2024 21:26:01 +0800
From: Weizhao Ouyang <o451686892@...il.com>
To: Mark Brown <broonie@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, linux-arm-kernel@...ts.infradead.org, 
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kselftest/arm64: abi: fix SVCR detection

On Mon, Dec 9, 2024 at 9:12 PM Mark Brown <broonie@...nel.org> wrote:
>
> On Mon, Dec 09, 2024 at 08:51:28PM +0800, Weizhao Ouyang wrote:
> > On Mon, Dec 9, 2024 at 8:36 PM Mark Brown <broonie@...nel.org> wrote:
>
> > > >       // Set SVCR if we're doing SME
> > > > -     cbz     x1, 1f
> > > >       adrp    x2, svcr_in
> > > >       ldr     x2, [x2, :lo12:svcr_in]
> > > > +     cbz     x1, 1f
> > > >       msr     S3_3_C4_C2_2, x2
>
> > > This is against an older verison of the code so wouldn't apply now.
> > > It's not also checking the value of SVCR, this is checking the SME flag
> > > the check is against x1.
>
> > This patch aims to fix the second check (SVCR_ZA_SHIFT) instead of
> > the first one (the x1 SME flag you're referring to):
>
> If we don't have SME we should be skipping over all the SME code and
> never even looking at the value of SVCR.  Looking at the current version
> of the code it does that, it branches to check_sve_in if SME is not
> enabled.

Hi Mark,

Yes we should skip it, this is just a minor tweak based on the
current implementation, after all, we manually passed its value by
svcr_in.

Which latest code version are you referring to? I think check_sve_in
is in fp testcase, not in the abi testcase. (checked the -next tree)

BR,
Weizhao