linux-kernel - Re: [PATCH] arm64: Add missing registrations of SF8MMx hwcaps

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Message-ID: <dae7f7b2-f066-4adc-974b-54649ba69306@sirena.org.uk>
Date: Mon, 10 Feb 2025 19:14:58 +0000
From: Mark Brown <broonie@...nel.org>
To: Mark Rutland <mark.rutland@....com>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: Add missing registrations of SF8MMx hwcaps

On Mon, Feb 10, 2025 at 06:41:09PM +0000, Mark Rutland wrote:
> On Mon, Feb 10, 2025 at 05:49:33PM +0000, Mark Brown wrote:
> > Commit 819935464cb2 ("arm64/hwcap: Describe 2024 dpISA extensions to
> > userspace") added definitions for HWCAP_F8MM8 and HWCAP_F8MM4 but did
> > not include the crucial registration in arm64_elf_hwcaps.  Add it.

> Looking again, it looks like KERNEL_HWCAP_FPRCVT also isn't wired up?

Indeed.  I'll add that separately.

> I did a quick check for suspects in that commit with:

> | [mark@...rids:~/src/linux]% git show 819935464cb2 | grep '^+\s' | grep -o 'KERNEL_HWCAP_[A-Z0-9_]\+' | sort | uniq -c | sort -n

> Checking against a tree based on v6.14-rc1, it superficially looks like
> we're not missing any other KERNEL_HWCAP_* bits per a coarse search,
> which shows three missing entries in cpufeature.c:

> | [mark@...rids:~/src/linux]% git grep -oh 'KERNEL_HWCAP_[A-Z0-9_]\+' -- arch/arm64/kernel/cpuinfo.c | sort | uniq | wc -l
> | 112
> | [mark@...rids:~/src/linux]% git grep -oh 'KERNEL_HWCAP_[A-Z0-9_]\+' -- arch/arm64/kernel/cpufeature.c | sort | uniq | wc -l
> | 109

> ... but maybe that misses something, and I haven't checked
> COMPAT_HWCAP(*) or COMPAT_HWCAP2(*).

> Could you please go check if there's anything else missing more generally?

The other two (on top of FPRCVT) are CPUID and EVTSTRM.  Both of these
are set using cpu_set_named_feature() which doesn't use match your grep
for KERNEL_HWCAP_ in cpufeature.c but instead generates the constant
name via token pasting.

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