RDMA/mlx5: Add DMAH object support

This patch introduces support for allocating and deallocating the DMAH
object.

Further details:
----------------
The DMAH API is exposed to upper layers only if the underlying device
supports TPH.

It uses the mlx5_core steering tag (ST) APIs to get a steering tag index
based on the provided input.

The obtained index is stored in the device-specific mlx5_dmah structure
for future use.

Upcoming patches in the series will integrate the allocated DMAH into
the memory region (MR) registration process.

Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/778550776799d82edb4d05da249a1cff00160b50.1752752567.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: yishaih

drivers/infiniband/hw/mlx5/Makefile

@@ -8,6 +8,7 @@ mlx5_ib-y := ah.o \
 	     cq.o \
 	     data_direct.o \
 	     dm.o \
+	     dmah.o \
 	     doorbell.o \
 	     fs.o \
 	     gsi.o \

drivers/infiniband/hw/mlx5/dmah.c

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+/*
+ * Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+
+#include <rdma/uverbs_std_types.h>
+#include <linux/pci-tph.h>
+#include "dmah.h"
+
+#define UVERBS_MODULE_NAME mlx5_ib
+#include <rdma/uverbs_named_ioctl.h>
+
+static int mlx5_ib_alloc_dmah(struct ib_dmah *ibdmah,
+			      struct uverbs_attr_bundle *attrs)
+{
+	struct mlx5_core_dev *mdev = to_mdev(ibdmah->device)->mdev;
+	struct mlx5_ib_dmah *dmah = to_mdmah(ibdmah);
+	u16 st_bits = BIT(IB_DMAH_CPU_ID_EXISTS) |
+		      BIT(IB_DMAH_MEM_TYPE_EXISTS);
+	int err;
+
+	/* PH is a must for TPH following PCIe spec 6.2-1.0 */
+	if (!(ibdmah->valid_fields & BIT(IB_DMAH_PH_EXISTS)))
+		return -EINVAL;
+
+	/* ST is optional; however, partial data for it is not allowed */
+	if (ibdmah->valid_fields & st_bits) {
+		if ((ibdmah->valid_fields & st_bits) != st_bits)
+			return -EINVAL;
+		err = mlx5_st_alloc_index(mdev, ibdmah->mem_type,
+					  ibdmah->cpu_id, &dmah->st_index);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int mlx5_ib_dealloc_dmah(struct ib_dmah *ibdmah,
+				struct uverbs_attr_bundle *attrs)
+{
+	struct mlx5_ib_dmah *dmah = to_mdmah(ibdmah);
+	struct mlx5_core_dev *mdev = to_mdev(ibdmah->device)->mdev;
+
+	if (ibdmah->valid_fields & BIT(IB_DMAH_CPU_ID_EXISTS))
+		return mlx5_st_dealloc_index(mdev, dmah->st_index);
+
+	return 0;
+}
+
+const struct ib_device_ops mlx5_ib_dev_dmah_ops = {
+	.alloc_dmah = mlx5_ib_alloc_dmah,
+	.dealloc_dmah = mlx5_ib_dealloc_dmah,
+};

drivers/infiniband/hw/mlx5/dmah.h

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */
+/*
+ * Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+
+#ifndef _MLX5_IB_DMAH_H
+#define _MLX5_IB_DMAH_H
+
+#include "mlx5_ib.h"
+
+extern const struct ib_device_ops mlx5_ib_dev_dmah_ops;
+
+struct mlx5_ib_dmah {
+	struct ib_dmah ibdmah;
+	u16 st_index;
+};
+
+static inline struct mlx5_ib_dmah *to_mdmah(struct ib_dmah *ibdmah)
+{
+	return container_of(ibdmah, struct mlx5_ib_dmah, ibdmah);
+}
+
+#endif /* _MLX5_IB_DMAH_H */

drivers/infiniband/hw/mlx5/main.c

@@ -50,6 +50,7 @@
 #include <rdma/ib_ucaps.h>
 #include "macsec.h"
 #include "data_direct.h"
+#include "dmah.h"
 
 #define UVERBS_MODULE_NAME mlx5_ib
 #include <rdma/uverbs_named_ioctl.h>
@@ -4181,6 +4182,7 @@ static const struct ib_device_ops mlx5_ib_dev_ops = {
 	INIT_RDMA_OBJ_SIZE(ib_ah, mlx5_ib_ah, ibah),
 	INIT_RDMA_OBJ_SIZE(ib_counters, mlx5_ib_mcounters, ibcntrs),
 	INIT_RDMA_OBJ_SIZE(ib_cq, mlx5_ib_cq, ibcq),
+	INIT_RDMA_OBJ_SIZE(ib_dmah, mlx5_ib_dmah, ibdmah),
 	INIT_RDMA_OBJ_SIZE(ib_pd, mlx5_ib_pd, ibpd),
 	INIT_RDMA_OBJ_SIZE(ib_qp, mlx5_ib_qp, ibqp),
 	INIT_RDMA_OBJ_SIZE(ib_srq, mlx5_ib_srq, ibsrq),
@@ -4308,6 +4310,9 @@ static int mlx5_ib_stage_caps_init(struct mlx5_ib_dev *dev)
 	    MLX5_GENERAL_OBJ_TYPES_CAP_SW_ICM)
 		ib_set_device_ops(&dev->ib_dev, &mlx5_ib_dev_dm_ops);
 
+	if (mdev->st)
+		ib_set_device_ops(&dev->ib_dev, &mlx5_ib_dev_dmah_ops);
+
 	ib_set_device_ops(&dev->ib_dev, &mlx5_ib_dev_ops);
 
 	if (IS_ENABLED(CONFIG_INFINIBAND_USER_ACCESS))