RE: [PATCH net] net: mana: Fix race of mana_hwc_post_rx_wqe and new hwc response

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> Subject: [PATCH net] net: mana: Fix race of mana_hwc_post_rx_wqe and new
> hwc response
> 
> The mana_hwc_rx_event_handler() / mana_hwc_handle_resp() calls
> complete(&ctx->comp_event) before posting the wqe back. It's possible that
> other callers, like mana_create_txq(), start the next round of
> mana_hwc_send_request() before the posting of wqe.
> And if the HW is fast enough to respond, it can hit no_wqe error on the HW
> channel, then the response message is lost. The mana driver may fail to create
> queues and open, because of waiting for the HW response and timed out.
> Sample dmesg:
> [  528.610840] mana 39d4:00:02.0: HWC: Request timed out!
> [  528.614452] mana 39d4:00:02.0: Failed to send mana message: -110, 0x0
> [  528.618326] mana 39d4:00:02.0 enP14804s2: Failed to create WQ object: -110
> 
> To fix it, move posting of rx wqe before complete(&ctx->comp_event).
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network
> Adapter (MANA)")
> Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>

Reviewed-by: Long Li <longli@xxxxxxxxxxxxx>

> ---
>  .../net/ethernet/microsoft/mana/hw_channel.c  | 62 ++++++++++---------
>  1 file changed, 34 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> index cafded2f9382..a00f915c5188 100644
> --- a/drivers/net/ethernet/microsoft/mana/hw_channel.c
> +++ b/drivers/net/ethernet/microsoft/mana/hw_channel.c
> @@ -52,9 +52,33 @@ static int mana_hwc_verify_resp_msg(const struct
> hwc_caller_ctx *caller_ctx,
>  	return 0;
>  }
> 
> +static int mana_hwc_post_rx_wqe(const struct hwc_wq *hwc_rxq,
> +				struct hwc_work_request *req)
> +{
> +	struct device *dev = hwc_rxq->hwc->dev;
> +	struct gdma_sge *sge;
> +	int err;
> +
> +	sge = &req->sge;
> +	sge->address = (u64)req->buf_sge_addr;
> +	sge->mem_key = hwc_rxq->msg_buf->gpa_mkey;
> +	sge->size = req->buf_len;
> +
> +	memset(&req->wqe_req, 0, sizeof(struct gdma_wqe_request));
> +	req->wqe_req.sgl = sge;
> +	req->wqe_req.num_sge = 1;
> +	req->wqe_req.client_data_unit = 0;
> +
> +	err = mana_gd_post_and_ring(hwc_rxq->gdma_wq, &req->wqe_req,
> NULL);
> +	if (err)
> +		dev_err(dev, "Failed to post WQE on HWC RQ: %d\n", err);
> +	return err;
> +}
> +
>  static void mana_hwc_handle_resp(struct hw_channel_context *hwc, u32
> resp_len,
> -				 const struct gdma_resp_hdr *resp_msg)
> +				 struct hwc_work_request *rx_req)
>  {
> +	const struct gdma_resp_hdr *resp_msg = rx_req->buf_va;
>  	struct hwc_caller_ctx *ctx;
>  	int err;
> 
> @@ -62,6 +86,7 @@ static void mana_hwc_handle_resp(struct
> hw_channel_context *hwc, u32 resp_len,
>  		      hwc->inflight_msg_res.map)) {
>  		dev_err(hwc->dev, "hwc_rx: invalid msg_id = %u\n",
>  			resp_msg->response.hwc_msg_id);
> +		mana_hwc_post_rx_wqe(hwc->rxq, rx_req);
>  		return;
>  	}
> 
> @@ -75,30 +100,13 @@ static void mana_hwc_handle_resp(struct
> hw_channel_context *hwc, u32 resp_len,
>  	memcpy(ctx->output_buf, resp_msg, resp_len);
>  out:
>  	ctx->error = err;
> -	complete(&ctx->comp_event);
> -}
> -
> -static int mana_hwc_post_rx_wqe(const struct hwc_wq *hwc_rxq,
> -				struct hwc_work_request *req)
> -{
> -	struct device *dev = hwc_rxq->hwc->dev;
> -	struct gdma_sge *sge;
> -	int err;
> -
> -	sge = &req->sge;
> -	sge->address = (u64)req->buf_sge_addr;
> -	sge->mem_key = hwc_rxq->msg_buf->gpa_mkey;
> -	sge->size = req->buf_len;
> 
> -	memset(&req->wqe_req, 0, sizeof(struct gdma_wqe_request));
> -	req->wqe_req.sgl = sge;
> -	req->wqe_req.num_sge = 1;
> -	req->wqe_req.client_data_unit = 0;
> +	/* Must post rx wqe before complete(), otherwise the next rx may
> +	 * hit no_wqe error.
> +	 */
> +	mana_hwc_post_rx_wqe(hwc->rxq, rx_req);
> 
> -	err = mana_gd_post_and_ring(hwc_rxq->gdma_wq, &req->wqe_req,
> NULL);
> -	if (err)
> -		dev_err(dev, "Failed to post WQE on HWC RQ: %d\n", err);
> -	return err;
> +	complete(&ctx->comp_event);
>  }
> 
>  static void mana_hwc_init_event_handler(void *ctx, struct gdma_queue *q_self,
> @@ -235,14 +243,12 @@ static void mana_hwc_rx_event_handler(void *ctx,
> u32 gdma_rxq_id,
>  		return;
>  	}
> 
> -	mana_hwc_handle_resp(hwc, rx_oob->tx_oob_data_size, resp);
> +	mana_hwc_handle_resp(hwc, rx_oob->tx_oob_data_size, rx_req);
> 
> -	/* Do no longer use 'resp', because the buffer is posted to the HW
> -	 * in the below mana_hwc_post_rx_wqe().
> +	/* Can no longer use 'resp', because the buffer is posted to the HW
> +	 * in mana_hwc_handle_resp() above.
>  	 */
>  	resp = NULL;
> -
> -	mana_hwc_post_rx_wqe(hwc_rxq, rx_req);
>  }
> 
>  static void mana_hwc_tx_event_handler(void *ctx, u32 gdma_txq_id,
> --
> 2.34.1






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