From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Eric Biederman <ebiederm@xmission.com>,
Kees Cook <keescook@chromium.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 0/4] arm64: Add AT_HWCAP3
Date: Wed, 6 Jul 2022 10:02:46 +0100 [thread overview]
Message-ID: <YsVPtuc50JhkOT9m@arm.com> (raw)
In-Reply-To: <YsR6n+AxQM289EMq@sirena.org.uk>
The 07/05/2022 18:53, Mark Brown wrote:
> On Mon, Jun 20, 2022 at 01:54:47PM +0100, Mark Brown wrote:
> > Currently for arm64 we expose hwcaps to userspace using the low 32 bits
> > of AT_HWCAP and AT_HWCAP2. Due to the ever expanding capabilties of the
> > architecture we have now allocated all the available bits in this scheme
> > so we need to expand, either using the higher bits or adding a new
> > AT_HWCAP3. Discussions with glibc developers suggested that AT_HWCAP3
> > would be cleaner for them so the series adopts that approach.
>
> This discussion appears to have ground to a halt. Szabolcs prefers
> AT_HWCAP3, Catalin using the high bits of AT_HWCAP2 for now and nobody
> else said anything. I don't have strong preferences either way but
> wonder if it's worth defining AT_HWCAP3 even if we start allocating more
> bits from AT_HWCAP2 so that it's got more time to percolate through
> libcs and so on before it's actually needed.
>
> What should we do here?
AT_HWCAP2 top bits works for me too.
then i'd do AT_HWCAP3 when we run out of hwcap2 bits.
i don't think defining AT_HWCAP3 without having any
hwcap3 bit is very useful.
this way we can postpone AT_HWCAP3 a bit and avoid
issues with top bits of plain AT_HWCAP in glibc.
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next prev parent reply other threads:[~2022-07-06 9:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-20 12:54 [PATCH v2 0/4] arm64: Add AT_HWCAP3 Mark Brown
2022-06-20 12:54 ` [PATCH v2 1/4] arm64/cpufeature: Store elf_hwcaps as an array rather than unsigned long Mark Brown
2022-06-28 14:21 ` Will Deacon
2022-06-28 15:06 ` Mark Brown
2022-06-29 10:01 ` Szabolcs Nagy
2022-06-29 11:44 ` Mark Brown
2022-06-29 12:06 ` Szabolcs Nagy
2022-06-29 13:55 ` Catalin Marinas
2022-06-29 15:07 ` Mark Brown
2022-06-20 12:54 ` [PATCH v2 2/4] elf: Allow architectures to provide AT_HWCAP3 Mark Brown
2022-06-20 12:54 ` [PATCH v2 3/4] arm64/cpufeature: Support AT_HWCAP3 Mark Brown
2022-06-20 12:54 ` [PATCH v2 4/4] arm64/hwcap: Support FEAT_EBF16 Mark Brown
2022-07-05 17:53 ` [PATCH v2 0/4] arm64: Add AT_HWCAP3 Mark Brown
2022-07-06 9:02 ` Szabolcs Nagy [this message]
2022-07-06 10:08 ` Marc Zyngier
2022-07-06 13:48 ` Mark Brown
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