linux-kernel - Re: [RFC PATCH 13/27] KVM: arm64: Enable access to sanitized CPU features at EL2

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Message-ID: <20201123143954.GA578849@google.com>
Date:   Mon, 23 Nov 2020 14:39:54 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)" 
        <kvmarm@...ts.cs.columbia.edu>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" 
        <devicetree@...r.kernel.org>, kernel-team@...roid.com,
        android-kvm@...gle.com
Subject: Re: [RFC PATCH 13/27] KVM: arm64: Enable access to sanitized CPU
 features at EL2

On Monday 23 Nov 2020 at 13:22:23 (+0000), David Brazdil wrote:
> Could you help my understand why we need this?
> * Why do we need PI routines in the first place? Would my series that fixes
>   relocations in hyp code remove the need?
> * You added these aliases for the string routines because you were worried
>   somebody would change the implementation in arch/arm64/lib, right? But this
>   cache flush function is defined in hyp/nvhe. So why do we need to point to
>   the PI alias if we control the implementation?

Right, in the specific case of the __flush_dcache_area() function none
of the PI stuff is really needed I think. I did it this way to keep
things as consistent as possible with the host-side implementation, but
that is not required.

I understand this can cause confusion, so yes, I'll simplify this for
v2.

Cheers,
Quentin