Add an optional dma_buf_ops.get_pci_tph callback and a DMA-buf importer wrapper, dma_buf_get_pci_tph().
TPH is PCIe TLP Processing Hint. 8-bit ST and 16-bit Extended ST are distinct PCIe TPH namespaces, so the importer requests the namespace it can emit and the exporter returns the matching ST/PH tuple or -EOPNOTSUPP. dma_buf_get_pci_tph() is the importer entry point. It requires &dmabuf->resv to be held while the callback runs and returns -EOPNOTSUPP when the exporter does not provide PCI TPH metadata. The first user is VFIO_DEVICE_FEATURE_DMA_BUF_TPH in vfio-pci, with mlx5 as the first importer. Signed-off-by: Zhiping Zhang <[email protected]> --- drivers/dma-buf/dma-buf.c | 32 ++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 25 +++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index d504c636dc29..e8314ed240d3 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -939,6 +939,7 @@ dma_buf_pin_on_map(struct dma_buf_attachment *attach) * - dma_buf_unmap_attachment() * - dma_buf_vmap() * - dma_buf_vunmap() + * - dma_buf_get_pci_tph() * * 2. Importers must not hold the dma-buf reservation lock when calling these * functions: @@ -979,6 +980,7 @@ dma_buf_pin_on_map(struct dma_buf_attachment *attach) * - &dma_buf_ops.unmap_dma_buf() * - &dma_buf_ops.vmap() * - &dma_buf_ops.vunmap() + * - &dma_buf_ops.get_pci_tph() * * 3. Exporters must hold the dma-buf reservation lock when calling these * functions: @@ -1144,6 +1146,36 @@ void dma_buf_unpin(struct dma_buf_attachment *attach) } EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, "DMA_BUF"); +/** + * dma_buf_get_pci_tph - Retrieve PCIe TLP Processing Hint (TPH) metadata + * @dmabuf: DMA buffer to query + * @extended: false for 8-bit ST, true for 16-bit Extended ST + * @steering_tag: returns the raw steering tag for the requested namespace + * @ph: returns the TPH processing hint + * + * Wrapper for the optional &dma_buf_ops.get_pci_tph callback. + * + * Must be called with &dma_buf.resv held. Returns -EOPNOTSUPP if the + * exporter does not implement the callback or has no metadata for the + * requested namespace. + * + * The returned steering tag and processing hint are only valid until the + * exporter invalidates the current mapping (signalled to the importer via + * &dma_buf_attach_ops.move_notify). Importers must re-query after a new + * mapping is established following invalidation. + */ +int dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph) +{ + dma_resv_assert_held(dmabuf->resv); + + if (!dmabuf->ops->get_pci_tph) + return -EOPNOTSUPP; + + return dmabuf->ops->get_pci_tph(dmabuf, extended, steering_tag, ph); +} +EXPORT_SYMBOL_NS_GPL(dma_buf_get_pci_tph, "DMA_BUF"); + /** * dma_buf_map_attachment - Returns the scatterlist table of the attachment; * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d1203da56fc5..14e8eb61a62c 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -113,6 +113,29 @@ struct dma_buf_ops { */ void (*unpin)(struct dma_buf_attachment *attach); + /** + * @get_pci_tph: + * + * Retrieve PCIe TLP Processing Hint (TPH) steering metadata for + * this buffer so an importer can program a matching ST/PH hint on + * outbound TLPs targeting the exporter for peer-to-peer DMA. + * + * @dmabuf: DMA buffer for which to retrieve TPH metadata + * @extended: false for 8-bit ST, true for 16-bit Extended ST + * @steering_tag: Returns the raw TPH steering tag for the requested + * namespace + * @ph: Returns the TPH processing hint (2-bit value) + * + * Optional callback for dma_buf_get_pci_tph(). Called with + * &dma_buf.resv held. Returns 0 on success or -EOPNOTSUPP when + * the exporter has no metadata for the requested namespace. + * + * Returned metadata follows the lifetime rules documented for + * dma_buf_get_pci_tph(). + */ + int (*get_pci_tph)(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph); + /** * @map_dma_buf: * @@ -563,6 +586,8 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach); int dma_buf_pin(struct dma_buf_attachment *attach); void dma_buf_unpin(struct dma_buf_attachment *attach); +int dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph); struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info); -- 2.53.0-Meta
