linux-kernel - Re: [PATCH v3] drivers/perf: Add support for ARMv8.3-SPE

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Date:   Mon, 30 Nov 2020 09:55:12 +0000
From:   Will Deacon <will@...nel.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     Wei Li <liwei391@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Marc Zyngier <maz@...nel.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        guohanjun@...wei.com
Subject: Re: [PATCH v3] drivers/perf: Add support for ARMv8.3-SPE

On Fri, Nov 27, 2020 at 12:03:35PM +0000, Suzuki K Poulose wrote:
> On 11/27/20 6:03 AM, Wei Li wrote:
> > Armv8.3 extends the SPE by adding:
> > - Alignment field in the Events packet, and filtering on this event
> >    using PMSEVFR_EL1.
> > - Support for the Scalable Vector Extension (SVE).
> > 
> > The main additions for SVE are:
> > - Recording the vector length for SVE operations in the Operation Type
> >    packet. It is not possible to filter on vector length.
> > - Incomplete predicate and empty predicate fields in the Events packet,
> >    and filtering on these events using PMSEVFR_EL1.
> > 
> > Update the check of pmsevfr for empty/partial predicated SVE and
> > alignment event in SPE driver. For adaption by the version of SPE,
> > expose 'pmsver' as cap attribute to userspace.
> > 
> > Signed-off-by: Wei Li <liwei391@...wei.com>
> 
> nit: Do we need to update the Kconfig help text too ? Right now that says :
> 
> --
> 
> 
> tristate "Enable support for the ARMv8.2 Statistical Profiling Extension""
> ....
> 
> help
>   Enable perf support for the ARMv8.2 Statistical Profiling
>   Extension, which provides periodic sampling of operations in

I think it's ok as-is, to be honest. It identifies the version of the
architecture when the feature was introduced, and I think it's only
reasonable to assume that subsequent versions of the architecture might
add extensions.

Will