linux-kernel - Re: [PATCH v3 01/15] KVM: arm64: Check if running in VHE from kvm_host_owns_hyp

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Date:   Thu, 9 Dec 2021 10:10:54 +0000
From:   Will Deacon <will@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v3 01/15] KVM: arm64: Check if running in VHE from
 kvm_host_owns_hyp_mappings()

On Wed, Dec 01, 2021 at 05:03:55PM +0000, Quentin Perret wrote:
> The kvm_host_owns_hyp_mappings() function should return true if and only
> if the host kernel is responsible for creating the hypervisor stage-1
> mappings. That is only possible in standard non-VHE mode, or during boot
> in protected nVHE mode. But either way, non of this makes sense in VHE,
> so make sure to catch this case as well, hence making the function
> return sensible values in any context (VHE or not).
> 
> Suggested-by: Marc Zyngier <maz@...nel.org>
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  arch/arm64/kvm/mmu.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 326cdfec74a1..f8f1096a297f 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -239,6 +239,9 @@ void free_hyp_pgds(void)
>  
>  static bool kvm_host_owns_hyp_mappings(void)
>  {
> +	if (is_kernel_in_hyp_mode())
> +		return false;

This looks identical to:

https://lore.kernel.org/r/20211208152300.2478542-7-qperret@google.com

Will