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

Leon Romanovsky
2026-01-20T14:07:40Z

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>
---
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));

--
2.52.0