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

["yanjun.zhu" <yanjun.zhu@linux.dev>]

On 2/11/26 5:10 AM, Tom Sela wrote:
> Add tracking of unique Address Handle usage to provide visibility into
> active AH resource consumption. The implementation uses a hash table to

It seems that xa is used instead of hash table in your commit?

Zhu Yanjun

> 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;
>   }