[PATCH v2 16/23] vfio/pci: Change the DMA-buf exporter to use mapping_type

[Alistair Popple]

From: Jason Gunthorpe <jgg at nvidia.com>

Simple conversion to add a match_mapping() callback that offers an
exporter SGT mapping type. Later patches will add a physical address
exporter so go straight to adding the match_mapping() function.

The check for attachment->peer2peer is replaced with setting
exporter_requires_p2p=true. VFIO always uses MMIO memory.

Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
Signed-off-by: Alistair Popple <apopple at nvidia.com>
---
 drivers/vfio/pci/vfio_pci_dmabuf.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index c16f460c01d6..ebbdbcc6ecbf 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -27,9 +27,6 @@ static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf,
 {
 	struct vfio_pci_dma_buf *priv = dmabuf->priv;
 
-	if (!attachment->peer2peer)
-		return -EOPNOTSUPP;
-
 	if (priv->revoked)
 		return -ENODEV;
 
@@ -99,11 +96,30 @@ static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf)
 	kfree(priv);
 }
 
-static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
-	.attach = vfio_pci_dma_buf_attach,
+static const struct dma_buf_mapping_sgt_exp_ops vfio_pci_dma_buf_sgt_ops = {
 	.map_dma_buf = vfio_pci_dma_buf_map,
 	.unmap_dma_buf = vfio_pci_dma_buf_unmap,
+};
+
+static int vfio_pci_dma_buf_match_mapping(struct dma_buf_match_args *args)
+{
+	struct dma_buf_mapping_match sgt_match[1];
+
+	/*
+	 * MMIO, so the importer must accept P2P, but it need not be a PCI
+	 * device: iommufd attaches with its own non-PCI device and programs
+	 * physical addresses. Reachability is checked when mapping, by
+	 * dma_buf_phys_vec_to_sgt().
+	 */
+	sgt_match[0] = DMA_BUF_EMAPPING_SGT_REQUIRES_P2P(&vfio_pci_dma_buf_sgt_ops);
+
+	return dma_buf_match_mapping(args, sgt_match, ARRAY_SIZE(sgt_match));
+}
+
+static const struct dma_buf_ops vfio_pci_dmabuf_ops = {
+	.attach = vfio_pci_dma_buf_attach,
 	.release = vfio_pci_dma_buf_release,
+	.match_mapping = vfio_pci_dma_buf_match_mapping,
 };
 
 /*

-- 
2.54.0