linux-kernel - Re: [PATCH] arm64/sme: Add hwcap for Scalable Matrix Extension

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Message-ID: <3c242430-9f6c-0e04-91fc-10132e88df99@linux.alibaba.com>
Date:   Fri, 15 Apr 2022 10:30:30 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Jonathan Corbet <corbet@....net>,
        Joey Gouly <joey.gouly@....com>,
        Vincenzo Frascino <Vincenzo.Frascino@....com>,
        Mark Brown <broonie@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Fuad Tabba <tabba@...gle.com>,
        Mark Rutland <mark.rutland@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64/sme: Add hwcap for Scalable Matrix Extension

Hi Marc,

On 4/14/22 8:06 PM, Marc Zyngier wrote:
> On Thu, 14 Apr 2022 12:55:44 +0100,
> Tianjia Zhang <tianjia.zhang@...ux.alibaba.com> wrote:
>>
>> Allow userspace to detect support for SME (Scalable Matrix Extension)
>> by providing a hwcap for it, using the official feature name FEAT_SME,
>> declared in ARM DDI 0487H.a specification.
> 
> Err, not just that, for sure. What does this patch buys you on its
> own, given that the kernel doesn't implement anything yet and that all
> the SME instructions will UNDEF?
> 
> [1] is the real deal.
> 
> Thanks,
> 
> 	M.
> 
> [1] https://lore.kernel.org/r/20220408114328.1401034-1-broonie@kernel.org
> 

Thanks for your suggestion, I have a very simple scenario, I can see
whether the SME feature is supported in cpuinfo, it seems impractical at
the moment.

Kind regards,
Tianjia