[PATCH v2 1/2] KVM: arm64: Disable interrupts while walking userspace PTs

[Oliver Upton]

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 at kernel.org>
> Cc: stable at 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