On Mon, Jan 19, 2026 at 01:12:45PM +0100, Christian König wrote:
On 1/18/26 13:08, Leon Romanovsky wrote:
From: Leon Romanovsky leonro@nvidia.com
DMABUF ->pin() interface is called when the DMABUF importer perform its DMA mapping, so let's use this opportunity to check if DMABUF exporter revoked its buffer or not.
Signed-off-by: Leon Romanovsky leonro@nvidia.com
drivers/vfio/pci/vfio_pci_dmabuf.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c index d4d0f7d08c53..af9c315ddf71 100644 --- a/drivers/vfio/pci/vfio_pci_dmabuf.c +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c @@ -20,6 +20,20 @@ struct vfio_pci_dma_buf { u8 revoked : 1; }; +static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment) +{
- struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv;
- dma_resv_assert_held(priv->dmabuf->resv);
- return dma_buf_attachment_is_revoke(attachment) ? 0 : -EOPNOTSUPP;
It's probably better to do that check in vfio_pci_dma_buf_attach.
I assume you are proposing to add this check in both vfio_pci_dma_buf_attach() and vfio_pci_dma_buf_pin(). Otherwise, importers that lack .invalidate_mapping() will invoke dma_buf_pin() and will not fail.
And BTW the function vfio_pci_dma_buf_move() seems to be broken:
void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked) { struct vfio_pci_dma_buf *priv; struct vfio_pci_dma_buf *tmp;
lockdep_assert_held_write(&vdev->memory_lock); list_for_each_entry_safe(priv, tmp, &vdev->dmabufs, dmabufs_elm) { if (!get_file_active(&priv->dmabuf->file)) continue; if (priv->revoked != revoked) { dma_resv_lock(priv->dmabuf->resv, NULL); priv->revoked = revoked; dma_buf_move_notify(priv->dmabuf);A dma_buf_move_notify() just triggers asynchronous invalidation of the mapping!
You need to use dma_resv_wait() to wait for that to finish.
We (VFIO and IOMMUFD) followed the same pattern used in amdgpu_bo_move_notify(), which also does not wait.
I'll add wait here.
Thanks
dma_resv_unlock(priv->dmabuf->resv); } fput(priv->dmabuf->file); }}
Regards, Christian.
+}
+static void vfio_pci_dma_buf_unpin(struct dma_buf_attachment *attachment) +{
- /* Do nothing */
+}
static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf, struct dma_buf_attachment *attachment) { @@ -76,6 +90,8 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf) } static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
- .pin = vfio_pci_dma_buf_pin,
- .unpin = vfio_pci_dma_buf_unpin, .attach = vfio_pci_dma_buf_attach, .map_dma_buf = vfio_pci_dma_buf_map, .unmap_dma_buf = vfio_pci_dma_buf_unmap,