[PATCH v7 06/15] iommupt: Add unmap_pages op

[Pasha Tatashin]

On Thu, Oct 23, 2025 at 2:20 PM Jason Gunthorpe <jgg at nvidia.com> wrote:
>
> unmap_pages removes mappings and any fully contained interior tables from
> the given range. This follows the now-standard iommu_domain API definition
> where it does not split up larger page sizes into smaller. The caller must
> perform unmap only on ranges created by map or it must have somehow
> otherwise determined safe cut points (eg iommufd/vfio use iova_to_phys to
> scan for them)
>
> A future work will provide 'cut' which explicitly does the page size split
> if the HW can support it.

Are there plans to add "free" when a table becomes empty on an unmap?
Not sure what would be an efficient implementation for that, maybe a
refcnt for # entries in table?

> unmap is implemented with a recursive descent of the tree. If the caller
> provides a VA range that spans an entire table item then the table memory
> can be freed as well.
>
> If an entire table item can be freed then this version will also check the
> leaf-only level of the tree to ensure that all entries are present to
> generate -EINVAL. Many of the existing drivers don't do this extra check.
>
> This version sits under the iommu_domain_ops as unmap_pages() but does not
> require the external page size calculation. The implementation is actually
> unmap_range() and can do arbitrary ranges, internally handling all the
> validation and supporting any arrangment of page sizes. A future series
> can optimize __iommu_unmap() to take advantage of this.
>
> Freed page table memory is batched up in the gather and will be freed in
> the driver's iotlb_sync() callback after the IOTLB flush completes.
>
> Tested-by: Alejandro Jimenez <alejandro.j.jimenez at oracle.com>
> Reviewed-by: Kevin Tian <kevin.tian at intel.com>
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>

Reviewed-by: Pasha Tatashin <pasha.tatashin at soleen.com>