linux-kernel - Re: [PATCH 5/6] KVM: arm64: pkvm: Stub io map functions

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Message-ID: <20211208174906.GE820@willie-the-truck>
Date:   Wed, 8 Dec 2021 17:49:07 +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 5/6] KVM: arm64: pkvm: Stub io map functions

On Wed, Dec 08, 2021 at 03:22:58PM +0000, Quentin Perret wrote:
> Now that GICv2 is disabled in nVHE protected mode there should be no
> other reason for the host to use create_hyp_io_mappings() or
> kvm_phys_addr_ioremap(). Add sanity checks to make sure that assumption
> remains true looking forward.
> 
> Signed-off-by: Quentin Perret <qperret@...gle.com>
> ---
>  arch/arm64/kvm/mmu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 326cdfec74a1..605c104eb030 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -407,6 +407,9 @@ int create_hyp_io_mappings(phys_addr_t phys_addr, size_t size,
>  	unsigned long addr;
>  	int ret;
>  
> +	if (is_protected_kvm_enabled())
> +		return -EPERM;

Looks like the vGIC is the only caller, so no need to worry about anybody
relying on *kaddr being zeroed on failure.

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

Will