Re: [PATCH v2 10/19] iommufd/viommu: Add vdev_id helpers for IOMMU drivers

[Nicolin Chen]

On Mon, Oct 07, 2024 at 03:28:16PM -0300, Jason Gunthorpe wrote:
> On Mon, Oct 07, 2024 at 10:25:01AM -0700, Nicolin Chen wrote:
> 
> > This is for vdev/dev v.s. hwpt. We need the lock for viommu's
> > vdev xarray.
> > 
> > Yet, giving a 2nd thought, I feel the lock would be useless if
> > a driver tries to refer the returned vdev (with this helper)
> > after the vdev object is destroyed..
> > 
> > We could only note something similar that caller must be aware
> > of the life cycle of vdev itself..
> 
> Yes, I imagined you'd use the xa_lock for this an it solves both
> problems at once.

Ah! We don't even need a rwsem then..

Thanks!
Nicolin