Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

[Dave Hansen]

On 4/25/22 09:40, Jean-Philippe Brucker wrote:
> The problem is that we'd have to request the device driver to stop DMA
> before we can destroy the context and free the PASID. We did consider
> doing this in the release() MMU notifier, but there were concerns about
> blocking mmput() for too long (for example
> https://lore.kernel.org/linux-iommu/4d68da96-0ad5-b412-5987-2f7a6aa796c3@xxxxxxx/
> though I think there was a more recent discussion). We also need to drain
> the PRI and fault queues to get rid of all references to that PASID.

Is the concern truly about blocking mmput() itself?  Or, is it about
releasing the resources associated with the mm?