From: Oliver Upton <oliver.upton@linux.dev>
To: Marc Zyngier <maz@kernel.org>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
kvm@vger.kernel.org, James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
Quentin Perret <qperret@google.com>,
Sean Christopherson <seanjc@google.com>,
David Matlack <dmatlack@google.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v2 1/2] KVM: arm64: Disable interrupts while walking userspace PTs
Date: Thu, 16 Mar 2023 23:42:12 +0000 [thread overview]
Message-ID: <ZBOpVLEPEJazjyGD@linux.dev> (raw)
In-Reply-To: <20230316174546.3777507-2-maz@kernel.org>
Marc,
On Thu, Mar 16, 2023 at 05:45:45PM +0000, Marc Zyngier wrote:
> We walk the userspace PTs to discover what mapping size was
> used there. However, this can race against the userspace tables
> being freed, and we end-up in the weeds.
>
> Thankfully, the mm code is being generous and will IPI us when
> doing so. So let's implement our part of the bargain and disable
> interrupts around the walk. This ensures that nothing terrible
> happens during that time.
>
> We still need to handle the removal of the page tables before
> the walk. For that, allow get_user_mapping_size() to return an
> error, and make sure this error can be propagated all the way
> to the the exit handler.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Cc: stable@vger.kernel.org
Looks good. I've squashed in this meaningless diff to make use of an existing
helper.
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index e95593736ae3..3b9d4d24c361 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -691,7 +691,7 @@ static int get_user_mapping_size(struct kvm *kvm, u64 addr)
return -EFAULT;
/* Oops, the userspace PTs are gone... Replay the fault */
- if (!(pte & PTE_VALID))
+ if (!kvm_pte_valid(pte))
return -EAGAIN;
return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level));
--
Thanks,
Oliver
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next prev parent reply other threads:[~2023-03-16 23:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-16 17:45 [PATCH v2 0/2] KVM: arm64: Plug a couple of MM races Marc Zyngier
2023-03-16 17:45 ` [PATCH v2 1/2] KVM: arm64: Disable interrupts while walking userspace PTs Marc Zyngier
2023-03-16 23:42 ` Oliver Upton [this message]
2023-03-17 9:03 ` Marc Zyngier
2023-03-16 17:45 ` [PATCH v2 2/2] KVM: arm64: Check for kvm_vma_mte_allowed in the critical section Marc Zyngier
2023-03-17 1:20 ` [PATCH v2 0/2] KVM: arm64: Plug a couple of MM races Oliver Upton
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