linux-kernel - Re: [PATCH] arm64: cpufeature: Export Armv8.6 Matrix feature to userspace

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Message-ID: <6f175c28-1ac0-3da0-bbfa-a811a4adfed7@arm.com>
Date:   Tue, 29 Oct 2019 15:32:42 +0000
From:   Julien Grall <julien.grall@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, suzuki.poulose@....com,
        Dave.Martin@....com
Subject: Re: [PATCH] arm64: cpufeature: Export Armv8.6 Matrix feature to
 userspace

Hi Will,

On 29/10/2019 11:36, Will Deacon wrote:
> On Tue, Oct 29, 2019 at 11:26:41AM +0000, Julien Grall wrote:
>> On 29/10/2019 11:15, Will Deacon wrote:
>>> On Fri, Oct 25, 2019 at 06:10:56PM +0100, Julien Grall wrote:
>>>> This patch provides support for reporting the presence of Armv8.6
>>>> Matrix and its optional features to userspace.
>>>
>>> Are you sure this is 8.6 and not earlier?
>>
>> This was introduced by Armv8.6 see [1] but allowed to be used by Armv8.2 and
>> onwards.
> 
> That doesn't mean an awful lot though, especially then the features are
> referred to in the docs as things like "ARMv8.2-F64MM".

It is arguable. The feature were announced for Armv8.6 but made available for 
previous release.

Anyway, I can remove the "Armv8.6" bits if that's the concern.

Cheers,

-- 
Julien Grall