RDMA/efa: Add CQ with external memory support

Add an option to create CQ using external memory instead of allocating
in the driver. The memory can be passed from userspace by dmabuf fd and
an offset or a VA. One of the possible usages is creating CQs that
reside in accelerator memory, allowing low latency asynchronous direct
polling from the accelerator device. Add a capability bit to reflect on
the feature support.

Reviewed-by: Daniel Kranzdorf <[email protected]>
Reviewed-by: Yonatan Nachum <[email protected]>
Signed-off-by: Michael Margolin <[email protected]>
Link: https://patch.msgid.link/[email protected]
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Leon Romanovsky <[email protected]>

Author: mrgolin

drivers/infiniband/hw/efa/efa.h

@@ -107,6 +107,7 @@ struct efa_cq {
 	u16 cq_idx;
 	/* NULL when no interrupts requested */
 	struct efa_eq *eq;
+	struct ib_umem *umem;
 };
 
 struct efa_qp {
@@ -162,6 +163,8 @@ int efa_create_qp(struct ib_qp *ibqp, struct ib_qp_init_attr *init_attr,
 int efa_destroy_cq(struct ib_cq *ibcq, struct ib_udata *udata);
 int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 		  struct uverbs_attr_bundle *attrs);
+int efa_create_cq_umem(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
+		       struct ib_umem *umem, struct uverbs_attr_bundle *attrs);
 struct ib_mr *efa_reg_mr(struct ib_pd *ibpd, u64 start, u64 length,
 			 u64 virt_addr, int access_flags,
 			 struct ib_udata *udata);

drivers/infiniband/hw/efa/efa_main.c

@@ -372,6 +372,7 @@ static const struct ib_device_ops efa_dev_ops = {
 	.alloc_pd = efa_alloc_pd,
 	.alloc_ucontext = efa_alloc_ucontext,
 	.create_cq = efa_create_cq,
+	.create_cq_umem = efa_create_cq_umem,
 	.create_qp = efa_create_qp,
 	.create_user_ah = efa_create_ah,
 	.dealloc_pd = efa_dealloc_pd,

drivers/infiniband/hw/efa/efa_verbs.c

@@ -254,6 +254,7 @@ int efa_query_device(struct ib_device *ibdev,
 		resp.max_rdma_size = dev_attr->max_rdma_size;
 
 		resp.device_caps |= EFA_QUERY_DEVICE_CAPS_CQ_WITH_SGID;
+		resp.device_caps |= EFA_QUERY_DEVICE_CAPS_CQ_WITH_EXT_MEM;
 		if (EFA_DEV_CAP(dev, RDMA_READ))
 			resp.device_caps |= EFA_QUERY_DEVICE_CAPS_RDMA_READ;
 
@@ -1087,8 +1088,11 @@ int efa_destroy_cq(struct ib_cq *ibcq, struct ib_udata *udata)
 		xa_erase(&dev->cqs_xa, cq->cq_idx);
 		synchronize_irq(cq->eq->irq.irqn);
 	}
-	efa_free_mapped(dev, cq->cpu_addr, cq->dma_addr, cq->size,
-			DMA_FROM_DEVICE);
+
+	if (cq->umem)
+		ib_umem_release(cq->umem);
+	else
+		efa_free_mapped(dev, cq->cpu_addr, cq->dma_addr, cq->size, DMA_FROM_DEVICE);
 	return 0;
 }
 
@@ -1127,8 +1131,8 @@ static int cq_mmap_entries_setup(struct efa_dev *dev, struct efa_cq *cq,
 	return 0;
 }
 
-int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
-		  struct uverbs_attr_bundle *attrs)
+int efa_create_cq_umem(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
+		       struct ib_umem *umem, struct uverbs_attr_bundle *attrs)
 {
 	struct ib_udata *udata = &attrs->driver_udata;
 	struct efa_ucontext *ucontext = rdma_udata_to_drv_context(
@@ -1207,11 +1211,30 @@ int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 
 	cq->ucontext = ucontext;
 	cq->size = PAGE_ALIGN(cmd.cq_entry_size * entries * cmd.num_sub_cqs);
-	cq->cpu_addr = efa_zalloc_mapped(dev, &cq->dma_addr, cq->size,
-					 DMA_FROM_DEVICE);
-	if (!cq->cpu_addr) {
-		err = -ENOMEM;
-		goto err_out;
+
+	if (umem) {
+		if (umem->length < cq->size) {
+			ibdev_dbg(&dev->ibdev, "External memory too small\n");
+			err = -EINVAL;
+			goto err_free_mem;
+		}
+
+		if (!ib_umem_is_contiguous(umem)) {
+			ibdev_dbg(&dev->ibdev, "Non contiguous CQ unsupported\n");
+			err = -EINVAL;
+			goto err_free_mem;
+		}
+
+		cq->cpu_addr = NULL;
+		cq->dma_addr = ib_umem_start_dma_addr(umem);
+		cq->umem = umem;
+	} else {
+		cq->cpu_addr = efa_zalloc_mapped(dev, &cq->dma_addr, cq->size,
+						 DMA_FROM_DEVICE);
+		if (!cq->cpu_addr) {
+			err = -ENOMEM;
+			goto err_out;
+		}
 	}
 
 	params.uarn = cq->ucontext->uarn;
@@ -1228,15 +1251,17 @@ int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 
 	err = efa_com_create_cq(&dev->edev, &params, &result);
 	if (err)
-		goto err_free_mapped;
+		goto err_free_mem;
 
 	resp.db_off = result.db_off;
 	resp.cq_idx = result.cq_idx;
 	cq->cq_idx = result.cq_idx;
 	cq->ibcq.cqe = result.actual_depth;
 	WARN_ON_ONCE(entries != result.actual_depth);
 
-	err = cq_mmap_entries_setup(dev, cq, &resp, result.db_valid);
+	if (!umem)
+		err = cq_mmap_entries_setup(dev, cq, &resp, result.db_valid);
+
 	if (err) {
 		ibdev_dbg(ibdev, "Could not setup cq[%u] mmap entries\n",
 			  cq->cq_idx);
@@ -1274,15 +1299,23 @@ int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 	efa_cq_user_mmap_entries_remove(cq);
 err_destroy_cq:
 	efa_destroy_cq_idx(dev, cq->cq_idx);
-err_free_mapped:
-	efa_free_mapped(dev, cq->cpu_addr, cq->dma_addr, cq->size,
-			DMA_FROM_DEVICE);
+err_free_mem:
+	if (umem)
+		ib_umem_release(umem);
+	else
+		efa_free_mapped(dev, cq->cpu_addr, cq->dma_addr, cq->size, DMA_FROM_DEVICE);
 
 err_out:
 	atomic64_inc(&dev->stats.create_cq_err);
 	return err;
 }
 
+int efa_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
+		  struct uverbs_attr_bundle *attrs)
+{
+	return efa_create_cq_umem(ibcq, attr, NULL, attrs);
+}
+
 static int umem_to_page_list(struct efa_dev *dev,
 			     struct ib_umem *umem,
 			     u64 *page_list,

include/uapi/rdma/efa-abi.h

@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) */
 /*
- * Copyright 2018-2024 Amazon.com, Inc. or its affiliates. All rights reserved.
+ * Copyright 2018-2025 Amazon.com, Inc. or its affiliates. All rights reserved.
  */
 
 #ifndef EFA_ABI_USER_H
@@ -131,6 +131,7 @@ enum {
 	EFA_QUERY_DEVICE_CAPS_DATA_POLLING_128 = 1 << 4,
 	EFA_QUERY_DEVICE_CAPS_RDMA_WRITE = 1 << 5,
 	EFA_QUERY_DEVICE_CAPS_UNSOLICITED_WRITE_RECV = 1 << 6,
+	EFA_QUERY_DEVICE_CAPS_CQ_WITH_EXT_MEM = 1 << 7,
 };
 
 struct efa_ibv_ex_query_device_resp {