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

[Marc Zyngier]

On 2023-03-16 23:42, Oliver Upton wrote:
> 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;

Sure, LGTM.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...