{"id":2215643,"url":"http://patchwork.ozlabs.org/api/covers/2215643/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/cover/20260324234615.3731237-1-zhipingz@meta.com/","project":{"id":28,"url":"http://patchwork.ozlabs.org/api/projects/28/?format=json","name":"Linux PCI development","link_name":"linux-pci","list_id":"linux-pci.vger.kernel.org","list_email":"linux-pci@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260324234615.3731237-1-zhipingz@meta.com>","list_archive_url":null,"date":"2026-03-24T23:46:01","name":"[RFC,v2,0/2] Retrieve tph from dmabuf for PCIe P2P memory access","submitter":{"id":92088,"url":"http://patchwork.ozlabs.org/api/people/92088/?format=json","name":"Zhiping Zhang","email":"zhipingz@meta.com"},"mbox":"http://patchwork.ozlabs.org/project/linux-pci/cover/20260324234615.3731237-1-zhipingz@meta.com/mbox/","series":[{"id":497360,"url":"http://patchwork.ozlabs.org/api/series/497360/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-pci/list/?series=497360","date":"2026-03-24T23:46:02","name":"Retrieve tph from dmabuf for PCIe P2P memory access","version":2,"mbox":"http://patchwork.ozlabs.org/series/497360/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/covers/2215643/comments/","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=meta.com header.i=@meta.com header.a=rsa-sha256\n header.s=s2048-2025-q2 header.b=CdOCU4Nn;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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the\nACPI check is in place to query and obtain the supported tph settings. Here\nwe intend to use the tph info to improve RDMA NIC memory access on a vfio-based\naccelerator device via PCIe peer-to-peer. When an application registers a\nRDMA memory region with DMABUF for the RDMA NIC to access the device memory,\nthe tph info of the memory region can be retrieved and used to set the\nsteering tag / process hint (ph). Additional instructions or hints can be\npassed to the GPU or accelerator device for advanced memory operations,\nsuch as, read cache selection.\n\nNote this RFC is for the discussion on the direction and is not intended to be\na complete implementation. If no objection, we will convert it to a Patch set.\n\nChanges v1 -> v2:\n- Encode steering tag and ph in vfio_device_feature_dma_buf flags field\n instead of adding new uapi struct fields, to preserve ABI compatibility\n- Fix subject prefixes: \"Vfio:\" -> \"vfio:\", \"RMDA MLX5:\" -> \"RDMA/mlx5:\"\n- Fix raw steering tag vs st_index mismatch: get_tph() now returns a raw\n steering tag, and the mlx5 consumer converts it to an st_index via the\n new mlx5_st_alloc_index_by_tag() API\n- Fix @tph doc typo to @steering_tag in dma-buf.h\n- Remove unused variable, fix parameter alignment, fix trailing semicolon\n\nZhiping Zhang (2):\n vfio: add callback to get tph info for dmabuf\n RDMA/mlx5: get tph for p2p access when registering dmabuf mr\n\n drivers/infiniband/hw/mlx5/mr.c | 34 +++++++++++++++++++\n .../net/ethernet/mellanox/mlx5/core/lib/st.c | 23 +++++++++----\n drivers/vfio/pci/vfio_pci_dmabuf.c | 26 ++++++++++++--\n include/linux/dma-buf.h | 30 ++++++++++++++++\n include/linux/mlx5/driver.h | 7 ++++\n include/uapi/linux/vfio.h | 9 +++--\n 6 files changed, 118 insertions(+), 11 deletions(-)\n\n--\n2.52.0"}