IB/core: Introduce FRMR pools

Add a generic Fast Registration Memory Region pools mechanism to allow
drivers to optimize memory registration performance.
Drivers that have the ability to reuse MRs or their underlying HW
objects can take advantage of the mechanism to keep a 'handle' for those
objects and use them upon user request.
We assume that to achieve this goal a driver and its HW should implement
a modify operation for the MRs that is able to at least clear and set the
MRs and in more advanced implementations also support changing a subset
of the MRs properties.

The mechanism is built using an RB-tree consisting of pools, each pool
represents a set of MR properties that are shared by all of the MRs
residing in the pool and are unmodifiable by the vendor driver or HW.

The exposed API from ib_core to the driver has 4 operations:
Init and cleanup - handles data structs and locks for the pools.
Push and pop - store and retrieve 'handle' for a memory registration
or deregistrations request.

The FRMR pools mechanism implements the logic to search the RB-tree for
a pool with matching properties and create a new one when needed and
requires the driver to implement creation and destruction of a 'handle'
when pool is empty or a handle is requested or is being destroyed.

Later patch will introduce Netlink API to interact with the FRMR pools
mechanism to allow users to both configure and track its usage.
A vendor wishing to configure FRMR pool without exposing it or without
exposing internal MR properties to users, should use the
kernel_vendor_key field in the pools key. This can be useful in a few
cases, e.g, when the FRMR handle has a vendor-specific un-modifiable
property that the user registering the memory might not be aware of.

Signed-off-by: Michael Guralnik <michaelgur@nvidia.com>
Reviewed-by: Yishai Hadas <yishaih@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20260226-frmr_pools-v4-2-95360b54f15e@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

2 files changed, 45 insertions, 0 deletions

diff --git a/include/rdma/frmr_pools.h b/include/rdma/frmr_pools.h
new file mode 100644
index 000000000000..9ef41eb43e4b
--- /dev/null
+++ b/include/rdma/frmr_pools.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+ *
+ * Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ */
+
+#ifndef FRMR_POOLS_H
+#define FRMR_POOLS_H
+
+#include <linux/types.h>
+#include <asm/page.h>
+
+struct ib_device;
+struct ib_mr;
+
+struct ib_frmr_key {
+	u64 vendor_key;
+	/* A pool with non-zero kernel_vendor_key is a kernel-only pool. */
+	u64 kernel_vendor_key;
+	size_t num_dma_blocks;
+	int access_flags;
+	u8 ats:1;
+};
+
+struct ib_frmr_pool_ops {
+	int (*create_frmrs)(struct ib_device *device, struct ib_frmr_key *key,
+			    u32 *handles, u32 count);
+	void (*destroy_frmrs)(struct ib_device *device, u32 *handles,
+			      u32 count);
+};
+
+int ib_frmr_pools_init(struct ib_device *device,
+		       const struct ib_frmr_pool_ops *pool_ops);
+void ib_frmr_pools_cleanup(struct ib_device *device);
+int ib_frmr_pool_pop(struct ib_device *device, struct ib_mr *mr);
+int ib_frmr_pool_push(struct ib_device *device, struct ib_mr *mr);
+
+#endif /* FRMR_POOLS_H */
diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
index 1b77fd88d0fb..ba34b131e9be 100644
--- a/include/rdma/ib_verbs.h
+++ b/include/rdma/ib_verbs.h
@@ -44,6 +44,7 @@
 #include <uapi/rdma/rdma_user_ioctl.h>
 #include <uapi/rdma/ib_user_ioctl_verbs.h>
 #include <linux/pci-tph.h>
+#include <rdma/frmr_pools.h>
 #include <linux/dma-buf.h>
 
 #define IB_FW_VERSION_NAME_MAX	ETHTOOL_FWVERS_LEN
@@ -1905,6 +1906,11 @@ struct ib_mr {
 	struct ib_dm      *dm;
 	struct ib_sig_attrs *sig_attrs; /* only for IB_MR_TYPE_INTEGRITY MRs */
 	struct ib_dmah *dmah;
+	struct {
+		struct ib_frmr_pool *pool;
+		struct ib_frmr_key key;
+		u32 handle;
+	} frmr;
 	/*
 	 * Implementation details of the RDMA core, don't use in drivers:
 	 */
@@ -2907,6 +2913,8 @@ struct ib_device {
 	struct list_head subdev_list;
 
 	enum rdma_nl_name_assign_type name_assign_type;
+
+	struct ib_frmr_pools *frmr_pools;
 };
 
 static inline void *rdma_zalloc_obj(struct ib_device *dev, size_t size,