linux-kernel - Re: [PATCH v2 0/2] KVM: arm64: Support for Arm v8.8 memcpy instructions in KVM guests

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Message-ID: <ZRX7-EJ9w-Nmyxjz@linux.dev>
Date:   Thu, 28 Sep 2023 22:19:36 +0000
From:   Oliver Upton <oliver.upton@...ux.dev>
To:     Kristina Martsenko <kristina.martsenko@....com>
Cc:     kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Colton Lewis <coltonlewis@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] KVM: arm64: Support for Arm v8.8 memcpy
 instructions in KVM guests

On Thu, Sep 28, 2023 at 05:55:39PM +0100, Kristina Martsenko wrote:

[...]

> > Perhaps I'm being pedantic, but I'd really like for there to be some
> > documentation that suggests MOPS exceptions can happen due to context
> > migration done by a higher EL as that is the only option in the context
> > of virtualization.
> 
> That's a good point. This shouldn't affect Linux guests as Linux is
> always able to handle a MOPS exception coming from EL0. But it would
> affect any non-Linux guest that pins all its EL0 tasks and doesn't
> implement a handler. It's not clear to me what the expectation for
> guests is, I'll ask the architects to clarify and get back to you.

That'd be excellent, thanks! All I'm looking for is something to point
folks at if/when they complain about MOPS behavior in KVM guests.

-- 
Thanks,
Oliver