[PATCH v2 0/2] vfio/dma-buf: add TPH support for peer-to-peer access

[Zhiping Zhang <zhipingz@meta.com>]

This series adds TLP Processing Hints (TPH) support to the VFIO dma-buf
export path, allowing importing drivers (e.g. mlx5) to use the exporter's
steering tag when performing peer-to-peer DMA into a VFIO-owned device.

Changes since v1:
  - VFIO_DEVICE_FEATURE_DMA_BUF is now unchanged — dma_ranges[],
    __counted_by(nr_ranges), and flags==0 are all preserved
  - Added a new VFIO_DEVICE_FEATURE_DMA_BUF_TPH (feature 13) as a separate
    SET ioctl that takes a dmabuf fd, validates it belongs to this vfio
    device, and stores the steering tag + processing hint under memory_lock
  - Kept the dma_buf_ops.get_tph callback as the general exporter-side
    interface for importing drivers

Patch 1 adds the dma-buf get_tph callback and the new vfio uAPI.
Patch 2 wires up the mlx5 RDMA driver as a consumer.

Previous links:
https://lore.kernel.org/linux-pci/20260324234615.3731237-1-zhipingz@meta.com/
https://lore.kernel.org/dri-devel/20260420183920.3626389-1-zhipingz@meta.com/

Zhiping Zhang (2):
  vfio: add dma-buf get_tph callback and DMA_BUF_TPH feature
  RDMA/mlx5: get tph for p2p access when registering dma-buf mr

 drivers/infiniband/hw/mlx5/mr.c                   |  38 +++++++
 drivers/net/ethernet/mellanox/mlx5/core/lib/st.c  |  25 +++--
 drivers/vfio/pci/vfio_pci_core.c                  |   3 +
 drivers/vfio/pci/vfio_pci_dmabuf.c                |  65 ++++++++++++
 drivers/vfio/pci/vfio_pci_priv.h                  |  11 ++
 include/linux/dma-buf.h                           |  17 +++
 include/linux/mlx5/driver.h                       |   7 ++
 include/uapi/linux/vfio.h                         |  22 ++++
 8 files changed, 180 insertions(+), 8 deletions(-)

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2.47.1