Subject: Re: [PATCH v3 5/8] RDMA/bng_re: Add infrastructure for enabling Firmware channel

From: Simon Horman <[email-masked]>
Date: Mon, 24 Nov 2025 16:44:21 +0000

On Mon, Nov 17, 2025 at 05:11:23PM +0000, Siva Reddy Kallam wrote:

...

> diff --git a/drivers/infiniband/hw/bng_re/bng_dev.c b/drivers/infiniband/hw/bng_re/bng_dev.c

...

> @@ -105,6 +105,69 @@ static void bng_re_fill_fw_msg(struct bnge_fw_msg *fw_msg, void *msg,
>  	fw_msg->timeout = timeout;
>  }
>  
> +static int bng_re_net_ring_free(struct bng_re_dev *rdev,
> +				u16 fw_ring_id, int type)
> +{
> +	struct bnge_auxr_dev *aux_dev = rdev->aux_dev;

Hi Siva,

rdev is dereferenced unconditionally here...

> +	struct hwrm_ring_free_input req = {};
> +	struct hwrm_ring_free_output resp;
> +	struct bnge_fw_msg fw_msg = {};
> +	int rc = -EINVAL;
> +
> +	if (!rdev)
> +		return rc;

... but it is assumed that rdev may be NULL here.

This does not seem consistent.

IMHO a good approach would be to drop this check, and the one below,
and only call bng_re_net_ring_free() in contexts where  rdev
and aux_dev are not NULL.

But I didn't look carefully to see if that idea matches the rest
of the code.

Flagged by Smatch.

> +
> +	if (!aux_dev)
> +		return rc;
> +
> +	bng_re_init_hwrm_hdr((void *)&req, HWRM_RING_FREE);
> +	req.ring_type = type;
> +	req.ring_id = cpu_to_le16(fw_ring_id);
> +	bng_re_fill_fw_msg(&fw_msg, (void *)&req, sizeof(req), (void *)&resp,
> +			    sizeof(resp), BNGE_DFLT_HWRM_CMD_TIMEOUT);
> +	rc = bnge_send_msg(aux_dev, &fw_msg);
> +	if (rc)
> +		ibdev_err(&rdev->ibdev, "Failed to free HW ring:%d :%#x",
> +			  req.ring_id, rc);
> +	return rc;
> +}

...

> diff --git a/drivers/infiniband/hw/bng_re/bng_fw.c b/drivers/infiniband/hw/bng_re/bng_fw.c

...

> +static int bng_re_process_qp_event(struct bng_re_rcfw *rcfw,
> +				   struct creq_qp_event *qp_event,
> +				   u32 *num_wait)
> +{
> +	struct bng_re_hwq *hwq = &rcfw->cmdq.hwq;
> +	struct bng_re_crsqe *crsqe;
> +	u32 req_size;
> +	u16 cookie;
> +	bool is_waiter_alive;
> +	struct pci_dev *pdev;
> +	u32 wait_cmds = 0;
> +	int rc = 0;

rc is always 0, so it may be slightly nicer to remove this variable and
simply return 0.

Flagged by Coccinelle.

> +
> +	pdev = rcfw->pdev;
> +	switch (qp_event->event) {
> +	case CREQ_QP_EVENT_EVENT_QP_ERROR_NOTIFICATION:
> +		dev_err(&pdev->dev, "Received QP error notification\n");
> +		break;
> +	default:
> +		/*
> +		 * Command Response
> +		 * cmdq->lock needs to be acquired to synchronie
> +		 * the command send and completion reaping. This function
> +		 * is always called with creq->lock held. Using
> +		 * the nested variant of spin_lock.
> +		 *
> +		 */
> +
> +		spin_lock_nested(&hwq->lock, SINGLE_DEPTH_NESTING);
> +		cookie = le16_to_cpu(qp_event->cookie);
> +		cookie &= BNG_FW_MAX_COOKIE_VALUE;
> +		crsqe = &rcfw->crsqe_tbl[cookie];
> +
> +		if (WARN_ONCE(test_bit(FIRMWARE_STALL_DETECTED,
> +				       &rcfw->cmdq.flags),
> +		    "Unreponsive rcfw channel detected.!!")) {
> +			dev_info(&pdev->dev,
> +				 "rcfw timedout: cookie = %#x, free_slots = %d",
> +				 cookie, crsqe->free_slots);
> +			spin_unlock(&hwq->lock);
> +			return rc;
> +		}
> +
> +		if (crsqe->is_waiter_alive) {
> +			if (crsqe->resp) {
> +				memcpy(crsqe->resp, qp_event, sizeof(*qp_event));
> +				/* Insert write memory barrier to ensure that
> +				 * response data is copied before clearing the
> +				 * flags
> +				 */
> +				smp_wmb();
> +			}
> +		}
> +
> +		wait_cmds++;
> +
> +		req_size = crsqe->req_size;
> +		is_waiter_alive = crsqe->is_waiter_alive;
> +
> +		crsqe->req_size = 0;
> +		if (!is_waiter_alive)
> +			crsqe->resp = NULL;
> +
> +		crsqe->is_in_used = false;
> +
> +		hwq->cons += req_size;
> +
> +		spin_unlock(&hwq->lock);
> +	}
> +	*num_wait += wait_cmds;
> +	return rc;
> +}

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