Re: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL for internal use

[Baolu Lu]

On 6/14/25 15:14, Nicolin Chen wrote:
> The access object has been used externally by VFIO mdev devices, allowing
> them to pin/unpin physical pages (via needs_pin_pages). Meanwhile, a racy
> unmap can occur in this case, so these devices usually implement an unmap
> handler, invoked by iommufd_access_notify_unmap().
>
> The new HW queue object will need the same pin/unpin feature, although it
> (unlike the mdev case) wants to reject any unmap attempt, during its life
> cycle.
>
> To reuse the access object for the new HW queue, allow its access->ops to
> be NULL. Error out a NULL access->ops in iommufd_access_notify_unmap() to
> reject an unmap operation and propagatethe errno upwards.
>
> Then, update iommufd_access_change_ioas() and iommufd_access_pin_pages(),
> to allow this new use case.
>
> Suggested-by: Jason Gunthorpe<jgg@xxxxxxxxxx>
> Signed-off-by: Nicolin Chen<nicolinc@xxxxxxxxxx>

Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>