iommufd: Add dma_buf_pin()

IOMMUFD relies on a private protocol with VFIO, and this always operated
in pinned mode.

Now that VFIO can support pinned importers update IOMMUFD to invoke the
normal dma-buf flow to request pin.

This isn't enough to allow IOMMUFD to work with other exporters, it still
needs a way to get the physical address list which is another series.

IOMMUFD supports the defined revoke semantics. It immediately stops and
fences access to the memory inside it's invalidate_mappings() callback,
and it currently doesn't use scatterlists so doesn't call map/unmap at
all.

It is expected that a future revision can synchronously call unmap from
the move_notify callback as well.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20260131-dmabuf-revoke-v7-8-463d956bd527@nvidia.com

diff --git a/drivers/iommu/iommufd/pages.c b/drivers/iommu/iommufd/pages.c
index 1d41ac625c982040dd8c97db450f2f9b98aa06c5..8124c554f2cc3793382dc27105b34a4a98dc2730 100644 (file)
--- a/drivers/iommu/iommufd/pages.c
+++ b/drivers/iommu/iommufd/pages.c
@@ -1502,16 +1502,22 @@ 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);
@@ -1657,6 +1663,7 @@ 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));