linux-kernel - Re: [PATCH v4 27/34] KVM: arm64: Always zero invalid PTEs

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Message-ID: <YEsxMgNncoVLdkjo@google.com>
Date:   Fri, 12 Mar 2021 09:15:30 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     catalin.marinas@....com, maz@...nel.org, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        android-kvm@...gle.com, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, tabba@...gle.com,
        mark.rutland@....com, dbrazdil@...gle.com, mate.toth-pal@....com,
        seanjc@...gle.com, robh+dt@...nel.org, ardb@...nel.org
Subject: Re: [PATCH v4 27/34] KVM: arm64: Always zero invalid PTEs

On Thursday 11 Mar 2021 at 17:33:38 (+0000), Will Deacon wrote:
> On Wed, Mar 10, 2021 at 05:57:44PM +0000, Quentin Perret wrote:
> > kvm_set_invalid_pte() currently only clears bit 0 from a PTE because
> > stage2_map_walk_table_post() needs to be able to follow the anchor. In
> > preparation for re-using bits 63-02 from invalid PTEs, make sure to zero
> 
> Why do you exclude bit 1 from this range?

Hmm, no good reason really. I wanted to play games with invalid table
mappings at some point, but dropped the idea and forgot to update the
commit message. My bad, I'll fix it up.

Thanks,
Quentin