linux-kernel - Re: [RFC PATCH 16/27] KVM: arm64: Prepare Hyp memory protection

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Message-ID: <X844CBNCTL4XT3iq@google.com>
Date:   Mon, 7 Dec 2020 14:11:20 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Will Deacon <will@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        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 16/27] KVM: arm64: Prepare Hyp memory protection

On Monday 07 Dec 2020 at 13:40:52 (+0000), Will Deacon wrote:
> Why not use the RESERVEDMEM_OF_DECLARE() interface for the hypervisor
> memory? That way, the hypervisor memory can either be statically partitioned
> as a carveout or allocated dynamically for us -- we wouldn't need to care.

Yup, I did consider that, but the actual amount of memory we need to
reserve for the hypervisor depends on things such as the size of struct
hyp_page, which depends on the kernel you're running (that is, it might
change over time). So, that really felt like something the kernel should
be doing, to keep the DT backward compatible, ... Or did you have
something more elaborate in mind?

Thanks,
Quentin