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From: Quentin Perret <qperret@google.com>
To: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
	Marc Zyngier <maz@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 4/5] KVM: arm64: Prevent re-finalisation of pKVM for a given CPU
Date: Wed, 29 Sep 2021 14:41:10 +0100	[thread overview]
Message-ID: <YVRs9nkIg3BZ6cVR@google.com> (raw)
In-Reply-To: <20210923112256.15767-5-will@kernel.org>

On Thursday 23 Sep 2021 at 12:22:55 (+0100), Will Deacon wrote:
> __pkvm_prot_finalize() completes the deprivilege of the host when pKVM
> is in use by installing a stage-2 translation table for the calling CPU.
> 
> Issuing the hypercall multiple times for a given CPU makes little sense,
> but in such a case just return early with -EPERM rather than go through
> the whole page-table dance again.
> 
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Quentin Perret <qperret@google.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index bacd493a4eac..cafe17e5fa8f 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -123,6 +123,9 @@ int __pkvm_prot_finalize(void)
>  	struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
>  	struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
>  
> +	if (params->hcr_el2 & HCR_VM)
> +		return -EPERM;

And you check this rather than the static key because we flip it upfront
I guess. Makes sense to me, but maybe a little comment would be useful :)
In any case:

Reviewed-by: Quentin Perret <qperret@google.com>

Thanks,
Quentin

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  reply	other threads:[~2021-09-29 13:42 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-23 11:22 [PATCH 0/5] KVM: arm64: Restrict host hypercalls when pKVM is enabled Will Deacon
2021-09-23 11:22 ` [PATCH 1/5] arm64: Prevent kexec and hibernation if is_protected_kvm_enabled() Will Deacon
2021-09-23 11:45   ` Mark Rutland
2021-09-23 12:29     ` Will Deacon
2021-09-23 11:22 ` [PATCH 2/5] KVM: arm64: Reject stub hypercalls after pKVM has been initialised Will Deacon
2021-09-29 13:37   ` Quentin Perret
2021-09-23 11:22 ` [PATCH 3/5] KVM: arm64: Propagate errors from __pkvm_prot_finalize hypercall Will Deacon
2021-09-29 13:36   ` Quentin Perret
2021-10-05 11:30     ` Will Deacon
2021-09-23 11:22 ` [PATCH 4/5] KVM: arm64: Prevent re-finalisation of pKVM for a given CPU Will Deacon
2021-09-29 13:41   ` Quentin Perret [this message]
2021-09-23 11:22 ` [PATCH 5/5] KVM: arm64: Disable privileged hypercalls after pKVM finalisation Will Deacon
2021-09-23 12:56   ` Marc Zyngier
2021-09-23 13:02     ` Will Deacon
2021-09-23 13:11       ` Marc Zyngier
2021-09-23 12:58   ` Will Deacon
2021-09-23 12:21 ` [PATCH 0/5] KVM: arm64: Restrict host hypercalls when pKVM is enabled Marc Zyngier

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