linux-kernel - Re: [PATCH v4 31/34] KVM: arm64: Wrap the host with a stage 2

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Date:   Thu, 11 Mar 2021 19:09:20 +0000
From:   Will Deacon <will@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
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 31/34] KVM: arm64: Wrap the host with a stage 2

On Wed, Mar 10, 2021 at 05:57:48PM +0000, Quentin Perret wrote:
> When KVM runs in protected nVHE mode, make use of a stage 2 page-table
> to give the hypervisor some control over the host memory accesses. The
> host stage 2 is created lazily using large block mappings if possible,
> and will default to page mappings in absence of a better solution.
> 
> From this point on, memory accesses from the host to protected memory
> regions (e.g. marked PROT_NONE) are fatal and lead to hyp_panic().
> 
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  arch/arm64/include/asm/kvm_asm.h              |   1 +
>  arch/arm64/include/asm/kvm_cpufeature.h       |   2 +
>  arch/arm64/kernel/image-vars.h                |   3 +
>  arch/arm64/kvm/arm.c                          |  10 +
>  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  34 +++
>  arch/arm64/kvm/hyp/nvhe/Makefile              |   2 +-
>  arch/arm64/kvm/hyp/nvhe/hyp-init.S            |   1 +
>  arch/arm64/kvm/hyp/nvhe/hyp-main.c            |  11 +
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c         | 246 ++++++++++++++++++
>  arch/arm64/kvm/hyp/nvhe/setup.c               |   5 +
>  arch/arm64/kvm/hyp/nvhe/switch.c              |   7 +-
>  arch/arm64/kvm/hyp/nvhe/tlb.c                 |   4 +-
>  12 files changed, 319 insertions(+), 7 deletions(-)
>  create mode 100644 arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
>  create mode 100644 arch/arm64/kvm/hyp/nvhe/mem_protect.c

I like this a lot more now, thanks:

Acked-by: Will Deacon <will@...nel.org>

Will