linux-kernel - Re: [PATCH v2 0/2] MTE support for KVM guest

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Message-ID: <c6043c5c-4bf1-e42c-1337-a892e6fd7402@linaro.org>
Date:   Thu, 10 Sep 2020 08:36:44 -0700
From:   Richard Henderson <richard.henderson@...aro.org>
To:     Steven Price <steven.price@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>
Cc:     James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Dave Martin <Dave.Martin@....com>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>, qemu-devel@...gnu.org,
        Juan Quintela <quintela@...hat.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        Peter Maydell <Peter.Maydell@....com>,
        Haibo Xu <Haibo.Xu@....com>
Subject: Re: [PATCH v2 0/2] MTE support for KVM guest

On 9/10/20 3:24 AM, Steven Price wrote:
> It is a shame, however I suspect this is because to use those instructions you
> need to know the block size held in GMID_EL1. And at least in theory that could
> vary between CPUs.

Which is no different from having to read DCZID_EL0 in order to implement
memset, in my opinion.  But, whatever.


> When we have some real hardware it would be worth profiling this. At the moment
> I've no idea whether the kernel entry overhead would make such an interface
> useful from a performance perspective or not.

Yep.


r~