[PATCH for-next] RDMA/efa: Add AH usage counter with sysfs exposure

[Tom Sela <tomsela@amazon.com>]

Add tracking of unique Address Handle usage to provide visibility into
active AH resource consumption. The implementation uses a hash table to
deduplicate identical AH requests that receive the same handle, ensuring
accurate resource counting.

The counter will be exposed via sysfs device attribute.

Reviewed-by: Michael Margolin <mrgolin@amazon.com>
Reviewed-by: Yonatan Nachum <ynachum@amazon.com>
Signed-off-by: Tom Sela <tomsela@amazon.com>
---
 drivers/infiniband/hw/efa/Makefile    |  4 +-
 drivers/infiniband/hw/efa/efa.h       |  5 ++-
 drivers/infiniband/hw/efa/efa_main.c  | 13 ++++++-
 drivers/infiniband/hw/efa/efa_sysfs.c | 33 ++++++++++++++++
 drivers/infiniband/hw/efa/efa_sysfs.h | 15 +++++++
 drivers/infiniband/hw/efa/efa_verbs.c | 56 ++++++++++++++++++++++++++-
 6 files changed, 120 insertions(+), 6 deletions(-)
 create mode 100644 drivers/infiniband/hw/efa/efa_sysfs.c
 create mode 100644 drivers/infiniband/hw/efa/efa_sysfs.h

diff --git a/drivers/infiniband/hw/efa/Makefile b/drivers/infiniband/hw/efa/Makefile
index 6e83083af0bc..0ba04eab17a1 100644
--- a/drivers/infiniband/hw/efa/Makefile
+++ b/drivers/infiniband/hw/efa/Makefile
@@ -1,9 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
-# Copyright 2018-2019 Amazon.com, Inc. or its affiliates. All rights reserved.
+# Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
 #
 # Makefile for Amazon Elastic Fabric Adapter (EFA) device driver.
 #
 
 obj-$(CONFIG_INFINIBAND_EFA) += efa.o
 
-efa-y := efa_com_cmd.o efa_com.o efa_main.o efa_verbs.o
+efa-y := efa_com_cmd.o efa_com.o efa_main.o efa_verbs.o efa_sysfs.o
diff --git a/drivers/infiniband/hw/efa/efa.h b/drivers/infiniband/hw/efa/efa.h
index 96f9c3bc98b2..d332bc4edcb7 100644
--- a/drivers/infiniband/hw/efa/efa.h
+++ b/drivers/infiniband/hw/efa/efa.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
 /*
- * Copyright 2018-2025 Amazon.com, Inc. or its affiliates. All rights reserved.
+ * Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
  */
 
 #ifndef _EFA_H_
@@ -69,6 +69,9 @@ struct efa_dev {
 
 	/* Only stores CQs with interrupts enabled */
 	struct xarray cqs_xa;
+	/* AH tracking xarray and counter*/
+	struct xarray ahs_xa;
+	atomic64_t ah_count;
 };
 
 struct efa_ucontext {
diff --git a/drivers/infiniband/hw/efa/efa_main.c b/drivers/infiniband/hw/efa/efa_main.c
index 6c415b9adb5f..3c6fa5af941a 100644
--- a/drivers/infiniband/hw/efa/efa_main.c
+++ b/drivers/infiniband/hw/efa/efa_main.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
 /*
- * Copyright 2018-2025 Amazon.com, Inc. or its affiliates. All rights reserved.
+ * Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
  */
 
 #include <linux/module.h>
@@ -12,6 +12,7 @@
 #include <rdma/uverbs_ioctl.h>
 
 #include "efa.h"
+#include "efa_sysfs.h"
 
 #define PCI_DEV_ID_EFA0_VF 0xefa0
 #define PCI_DEV_ID_EFA1_VF 0xefa1
@@ -561,6 +562,8 @@ static struct efa_dev *efa_probe_device(struct pci_dev *pdev)
 	edev->dmadev = &pdev->dev;
 	dev->pdev = pdev;
 	xa_init(&dev->cqs_xa);
+	xa_init(&dev->ahs_xa);
+	atomic64_set(&dev->ah_count, 0);
 
 	pci_mem_bars = pci_select_bars(pdev, IORESOURCE_MEM);
 	if (EFA_BASE_BAR_MASK & ~pci_mem_bars) {
@@ -619,8 +622,14 @@ static struct efa_dev *efa_probe_device(struct pci_dev *pdev)
 	if (err)
 		goto err_free_mgmnt_irq;
 
+	err = efa_sysfs_init(dev);
+	if (err)
+		goto err_admin_destroy;
+
 	return dev;
 
+err_admin_destroy:
+	efa_com_admin_destroy(edev);
 err_free_mgmnt_irq:
 	efa_free_irq(dev, &dev->admin_irq);
 err_disable_msix:
@@ -645,6 +654,7 @@ static void efa_remove_device(struct pci_dev *pdev,
 	struct efa_com_dev *edev;
 
 	edev = &dev->edev;
+	efa_sysfs_destroy(dev);
 	efa_com_dev_reset(edev, reset_reason);
 	efa_com_admin_destroy(edev);
 	efa_free_irq(dev, &dev->admin_irq);
@@ -653,6 +663,7 @@ static void efa_remove_device(struct pci_dev *pdev,
 	devm_iounmap(&pdev->dev, edev->reg_bar);
 	efa_release_bars(dev, EFA_BASE_BAR_MASK);
 	xa_destroy(&dev->cqs_xa);
+	xa_destroy(&dev->ahs_xa);
 	ib_dealloc_device(&dev->ibdev);
 	pci_disable_device(pdev);
 }
diff --git a/drivers/infiniband/hw/efa/efa_sysfs.c b/drivers/infiniband/hw/efa/efa_sysfs.c
new file mode 100644
index 000000000000..79602cf77424
--- /dev/null
+++ b/drivers/infiniband/hw/efa/efa_sysfs.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
+/*
+ * Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/sysfs.h>
+
+#include "efa_sysfs.h"
+
+static ssize_t ah_count_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct efa_dev *efa_dev = pci_get_drvdata(to_pci_dev(dev));
+
+	return sysfs_emit(buf, "%lld\n", atomic64_read(&efa_dev->ah_count));
+}
+
+static DEVICE_ATTR_RO(ah_count);
+
+int efa_sysfs_init(struct efa_dev *dev)
+{
+	struct device *device = &dev->pdev->dev;
+
+	if (device_create_file(device, &dev_attr_ah_count))
+		dev_err(device, "Failed to create AH count sysfs file\n");
+
+	return 0;
+}
+
+void efa_sysfs_destroy(struct efa_dev *dev)
+{
+	device_remove_file(&dev->pdev->dev, &dev_attr_ah_count);
+}
diff --git a/drivers/infiniband/hw/efa/efa_sysfs.h b/drivers/infiniband/hw/efa/efa_sysfs.h
new file mode 100644
index 000000000000..fda3a885c150
--- /dev/null
+++ b/drivers/infiniband/hw/efa/efa_sysfs.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause */
+/*
+ * Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
+ */
+
+#ifndef _EFA_SYSFS_H_
+#define _EFA_SYSFS_H_
+
+#include "efa.h"
+
+int efa_sysfs_init(struct efa_dev *dev);
+
+void efa_sysfs_destroy(struct efa_dev *dev);
+
+#endif /* _EFA_SYSFS_H_ */
diff --git a/drivers/infiniband/hw/efa/efa_verbs.c b/drivers/infiniband/hw/efa/efa_verbs.c
index 22d3e25c3b9d..1d8cb4a7f946 100644
--- a/drivers/infiniband/hw/efa/efa_verbs.c
+++ b/drivers/infiniband/hw/efa/efa_verbs.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
 /*
- * Copyright 2018-2024 Amazon.com, Inc. or its affiliates. All rights reserved.
+ * Copyright 2018-2026 Amazon.com, Inc. or its affiliates. All rights reserved.
  */
 
 #include <linux/dma-buf.h>
@@ -2104,6 +2104,51 @@ int efa_mmap(struct ib_ucontext *ibucontext,
 	return __efa_mmap(dev, ucontext, vma);
 }
 
+static int efa_add_ah(struct efa_dev *dev, u16 ah)
+{
+	unsigned long refcount;
+	void *entry;
+	int err;
+
+	xa_lock(&dev->ahs_xa);
+	entry = xa_load(&dev->ahs_xa, ah);
+	refcount = entry ? xa_to_value(entry) : 0;
+	if (refcount == 0)
+		atomic64_inc(&dev->ah_count);
+
+	err = xa_err(__xa_store(&dev->ahs_xa, ah, xa_mk_value(refcount + 1), GFP_ATOMIC));
+	xa_unlock(&dev->ahs_xa);
+
+	return err;
+}
+
+static int efa_remove_ah(struct efa_dev *dev, u16 ah)
+{
+	unsigned long refcount;
+	void *entry;
+	int err;
+
+	xa_lock(&dev->ahs_xa);
+	entry = xa_load(&dev->ahs_xa, ah);
+	refcount = entry ? xa_to_value(entry) : 0;
+	if (refcount == 0) {
+		/* AH already removed or never existed - unexpected but handle gracefully */
+		xa_unlock(&dev->ahs_xa);
+		return 0;
+	}
+
+	refcount--;
+
+	if (refcount == 0) {
+		err = xa_err(__xa_erase(&dev->ahs_xa, ah));
+		atomic64_dec(&dev->ah_count);
+	} else {
+		err = xa_err(__xa_store(&dev->ahs_xa, ah, xa_mk_value(refcount), GFP_ATOMIC));
+	}
+	xa_unlock(&dev->ahs_xa);
+	return err;
+}
+
 static int efa_ah_destroy(struct efa_dev *dev, struct efa_ah *ah)
 {
 	struct efa_com_destroy_ah_params params = {
@@ -2150,6 +2195,10 @@ int efa_create_ah(struct ib_ah *ibah,
 	memcpy(ah->id, ah_attr->grh.dgid.raw, sizeof(ah->id));
 	ah->ah = result.ah;
 
+	err = efa_add_ah(dev, ah->ah);
+	if (err)
+		goto err_destroy_ah;
+
 	resp.efa_address_handle = result.ah;
 
 	if (udata->outlen) {
@@ -2158,13 +2207,15 @@ int efa_create_ah(struct ib_ah *ibah,
 		if (err) {
 			ibdev_dbg(&dev->ibdev,
 				  "Failed to copy udata for create_ah response\n");
-			goto err_destroy_ah;
+			goto err_remove_ah;
 		}
 	}
 	ibdev_dbg(&dev->ibdev, "Created ah[%d]\n", ah->ah);
 
 	return 0;
 
+err_remove_ah:
+	efa_remove_ah(dev, ah->ah);
 err_destroy_ah:
 	efa_ah_destroy(dev, ah);
 err_out:
@@ -2185,6 +2236,7 @@ int efa_destroy_ah(struct ib_ah *ibah, u32 flags)
 		return -EOPNOTSUPP;
 	}
 
+	efa_remove_ah(dev, ah->ah);
 	efa_ah_destroy(dev, ah);
 	return 0;
 }
-- 
2.47.3