linux-kernel - Re: [PATCH v4 17/34] KVM: arm64: Elevate hypervisor mappings creation at EL2

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Date:   Thu, 11 Mar 2021 17:28:52 +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 17/34] KVM: arm64: Elevate hypervisor mappings
 creation at EL2

On Wed, Mar 10, 2021 at 05:57:34PM +0000, Quentin Perret wrote:
> Previous commits have introduced infrastructure to enable the EL2 code
> to manage its own stage 1 mappings. However, this was preliminary work,
> and none of it is currently in use.
> 
> Put all of this together by elevating the mapping creation at EL2 when
> memory protection is enabled. In this case, the host kernel running
> at EL1 still creates _temporary_ EL2 mappings, only used while
> initializing the hypervisor, but frees them right after.
> 
> As such, all calls to create_hyp_mappings() after kvm init has finished
> turn into hypercalls, as the host now has no 'legal' way to modify the
> hypevisor page tables directly.
> 
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  arch/arm64/include/asm/kvm_mmu.h |  2 +-
>  arch/arm64/kvm/arm.c             | 87 +++++++++++++++++++++++++++++---
>  arch/arm64/kvm/mmu.c             | 43 ++++++++++++++--
>  3 files changed, 120 insertions(+), 12 deletions(-)

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

Will