linux-kernel - Re: [PATCH v2 2/2] arm64: Expose Arm v8.4 features

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Message-ID: <20180226180521.GH26147@arm.com>
Date:   Mon, 26 Feb 2018 18:05:21 +0000
From:   Will Deacon <will.deacon@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, dave.martin@....com, mark.rutland@....com,
        marc.zyngier@....com, james.morse@....com
Subject: Re: [PATCH v2 2/2] arm64: Expose Arm v8.4 features

On Wed, Feb 07, 2018 at 02:21:06PM +0000, Suzuki K Poulose wrote:
> Expose the new features introduced by Arm v8.4 extensions to
> Arm v8-A profile.
> 
> These include :
> 
>  1) Data indpendent timing of instructions. (DIT, exposed as HWCAP_DIT)
>  2) Unaligned atomic instructions and Single-copy atomicity of loads
>     and stores. (AT, expose as HWCAP_USCAT)
>  3) LDAPR and STLR instructions with immediate offsets (extension to
>     LRCPC, exposed as HWCAP_ILRCPC)
>  4) Flag manipulation instructions (TS, exposed as HWCAP_FLAGM).

Please resend this but continuing with the default of FTR_STRICT, as we
currently have. That way this can be merged while we work out what we want
to do there.

> While at it get rid of the RES0 entries in the cpu-feature-registers.txt
> documentation, as:
>  1) We care only about the user visible fields.
>  2) The field may not be up-to-date
>  3) We already explain the rules of the fields if it is not visible.

Please spin this part as a separate patch.

Will