linux-kernel - Re: [PATCH 1/5] arm64: cpufeature: Add scope for capability check

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Message-ID: <570FD7C2.9030305@arm.com>
Date:	Thu, 14 Apr 2016 18:47:46 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Will Deacon <will.deacon@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	marc.zyngier@....com, catalin.marinas@....com,
	mark.rutland@....com, Vadim.Lomovtsev@...iumnetworks.com,
	James Morse <james.morse@....com>,
	Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH 1/5] arm64: cpufeature: Add scope for capability check

On 14/04/16 18:38, Will Deacon wrote:
> Hi Suzuki,
>
> On Wed, Apr 06, 2016 at 12:24:10PM +0100, Suzuki K Poulose wrote:
>> Add scope parameter to the arm64_cpu_capabilities::matches(),
>> so that this can be reused for checking the capability on a
>> given CPU vs the system wide. By default, the system uses
>> 'system' wide values for setting the CPU_HWCAPs and ELF_HWCAPs.

>>   static bool __maybe_unused
>> -is_affected_midr_range(const struct arm64_cpu_capabilities *entry)
>> +is_affected_midr_range(const struct arm64_cpu_capabilities *entry, int __unused)
>
> Maybe it would be better to WARN if somebody passes SCOPE_SYSTEM, rather
> than silently treat it as per-cpu?

Should we worry about errata's which may not necessarily depend on per CPU or
a local capability (GIC) ? If not, we could add a WARN after passing down LOCAL
scope for errata. Right now we always do SCOPE_SYSTEM from update_cpu_capabilities(), even for
cpu_errata table. There is no specific reason for that.

Cheers
Suzuki




>
> Will
>