[PATCH rc] iommu/arm-smmu-v3: Do not use GFP_KERNEL under as spinlock

[Jason Gunthorpe]

On Tue, Feb 13, 2024 at 11:20:15AM +0000, Will Deacon wrote:

> Damn, all the surrounding rework has really left this poor code in a bit
> of a state. 

That's one way to describe it. There is a reason it took me so many
patches to align this to the new core APIs :(

> Could you please respin your fix, but with an additional change
> to arm_smmu_mmu_notifier_get() so that it returns an error if there is
> more than one device in the domain, with some of the above in a comment?

Adding a check is not a comprehensive solution, there are still ways
userspace can attack this code with iommufd's coming PASID support. It
certainly doesn't belong in this patch which should be backported.

I can summarize some of these details in a comment for this patch.

Jason