Re: [PATCH v3 5/7] iommufd: Pin dma-buf importer for revoke semantics

Christian König
2026-01-21T09:01:50Z

On 1/20/26 15:07, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
>
> IOMMUFD does not support page fault handling, and after a call to
> .invalidate_mappings() all mappings become invalid. Ensure that
> the IOMMUFD dma-buf importer is bound to a revoke‑aware dma-buf
> exporter (for example, VFIO).
>
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>

I don't know the code well enough for a review, but that looks totally reasonable to me.

Acked-by: Christian König <christian.koenig@amd.com>

> ---
> drivers/iommu/iommufd/pages.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c
> index 76f900fa1687..a5eb2bc4ef48 100644
> --- a/drivers/iommu/iommufd/pages.c
> +++ b/drivers/iommu/iommufd/pages.c
> @@ -1501,16 +1501,22 @@ static int iopt_map_dmabuf(struct iommufd_ctx *ictx, struct iopt_pages *pages,
> mutex_unlock(&pages->mutex);
> }
>
> - rc = sym_vfio_pci_dma_buf_iommufd_map(attach, &pages->dmabuf.phys);
> + rc = dma_buf_pin(attach);
> if (rc)
> goto err_detach;
>
> + rc = sym_vfio_pci_dma_buf_iommufd_map(attach, &pages->dmabuf.phys);
> + if (rc)
> + goto err_unpin;
> +
> dma_resv_unlock(dmabuf->resv);
>
> /* On success iopt_release_pages() will detach and put the dmabuf. */
> pages->dmabuf.attach = attach;
> return 0;
>
> +err_unpin:
> + dma_buf_unpin(attach);
> err_detach:
> dma_resv_unlock(dmabuf->resv);
> dma_buf_detach(dmabuf, attach);
> @@ -1656,6 +1662,7 @@ void iopt_release_pages(struct kref *kref)
> if (iopt_is_dmabuf(pages) && pages->dmabuf.attach) {
> struct dma_buf *dmabuf = pages->dmabuf.attach->dmabuf;
>
> + dma_buf_unpin(pages->dmabuf.attach);
> dma_buf_detach(dmabuf, pages->dmabuf.attach);
> dma_buf_put(dmabuf);
> WARN_ON(!list_empty(&pages->dmabuf.tracker));
>