[PATCH v3 rdma-next] RDMA/qedr: SRQ's bug fixes

[PATCH v3 rdma-next] RDMA/qedr: SRQ's bug fixes

[Yuval Basson]

QP's with the same SRQ, working on different CQs and running in parallel
on different CPUs could lead to a race when maintaining the SRQ consumer
count, and leads to FW running out of SRQs. Update the consumer atomically.
Make sure the wqe_prod is updated after the sge_prod due to FW
requirements.

Fixes: 3491c9e799fb9 ("RDMA/qedr: Add support for kernel mode SRQ's")
Signed-off-by: Michal Kalderon <mkalderon@marvell.com>
Signed-off-by: Yuval Basson <ybason@marvell.com>

---
Change in v3:
 *Replace changelog

Changes in v2:
* Change barrier() to dma_wmb()
* Remove redundant dma_wmb()

 drivers/infiniband/hw/qedr/qedr.h  |  4 ++--
 drivers/infiniband/hw/qedr/verbs.c | 23 +++++++++++------------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/drivers/infiniband/hw/qedr/qedr.h b/drivers/infiniband/hw/qedr/qedr.h
index fdf90ec..aa33202 100644
--- a/drivers/infiniband/hw/qedr/qedr.h
+++ b/drivers/infiniband/hw/qedr/qedr.h
@@ -344,10 +344,10 @@ struct qedr_srq_hwq_info {
 	u32 wqe_prod;
 	u32 sge_prod;
 	u32 wr_prod_cnt;
-	u32 wr_cons_cnt;
+	atomic_t wr_cons_cnt;
 	u32 num_elems;
 
-	u32 *virt_prod_pair_addr;
+	struct rdma_srq_producers *virt_prod_pair_addr;
 	dma_addr_t phy_prod_pair_addr;
 };
 
diff --git a/drivers/infiniband/hw/qedr/verbs.c b/drivers/infiniband/hw/qedr/verbs.c
index 9b9e802..444537b 100644
--- a/drivers/infiniband/hw/qedr/verbs.c
+++ b/drivers/infiniband/hw/qedr/verbs.c
@@ -1510,6 +1510,7 @@ int qedr_create_srq(struct ib_srq *ibsrq, struct ib_srq_init_attr *init_attr,
 	srq->dev = dev;
 	hw_srq = &srq->hw_srq;
 	spin_lock_init(&srq->lock);
+	atomic_set(&hw_srq->wr_cons_cnt, 0);
 
 	hw_srq->max_wr = init_attr->attr.max_wr;
 	hw_srq->max_sges = init_attr->attr.max_sge;
@@ -3686,7 +3687,7 @@ static u32 qedr_srq_elem_left(struct qedr_srq_hwq_info *hw_srq)
 	 * count and consumer count and subtract it from max
 	 * work request supported so that we get elements left.
 	 */
-	used = hw_srq->wr_prod_cnt - hw_srq->wr_cons_cnt;
+	used = hw_srq->wr_prod_cnt - (u32)atomic_read(&hw_srq->wr_cons_cnt);
 
 	return hw_srq->max_wr - used;
 }
@@ -3701,7 +3702,6 @@ int qedr_post_srq_recv(struct ib_srq *ibsrq, const struct ib_recv_wr *wr,
 	unsigned long flags;
 	int status = 0;
 	u32 num_sge;
-	u32 offset;
 
 	spin_lock_irqsave(&srq->lock, flags);
 
@@ -3714,7 +3714,8 @@ int qedr_post_srq_recv(struct ib_srq *ibsrq, const struct ib_recv_wr *wr,
 		if (!qedr_srq_elem_left(hw_srq) ||
 		    wr->num_sge > srq->hw_srq.max_sges) {
 			DP_ERR(dev, "Can't post WR  (%d,%d) || (%d > %d)\n",
-			       hw_srq->wr_prod_cnt, hw_srq->wr_cons_cnt,
+			       hw_srq->wr_prod_cnt,
+			       atomic_read(&hw_srq->wr_cons_cnt),
 			       wr->num_sge, srq->hw_srq.max_sges);
 			status = -ENOMEM;
 			*bad_wr = wr;
@@ -3748,22 +3749,20 @@ int qedr_post_srq_recv(struct ib_srq *ibsrq, const struct ib_recv_wr *wr,
 			hw_srq->sge_prod++;
 		}
 
-		/* Flush WQE and SGE information before
+		/* Update WQE and SGE information before
 		 * updating producer.
 		 */
-		wmb();
+		dma_wmb();
 
 		/* SRQ producer is 8 bytes. Need to update SGE producer index
 		 * in first 4 bytes and need to update WQE producer in
 		 * next 4 bytes.
 		 */
-		*srq->hw_srq.virt_prod_pair_addr = hw_srq->sge_prod;
-		offset = offsetof(struct rdma_srq_producers, wqe_prod);
-		*((u8 *)srq->hw_srq.virt_prod_pair_addr + offset) =
-			hw_srq->wqe_prod;
+		srq->hw_srq.virt_prod_pair_addr->sge_prod = hw_srq->sge_prod;
+		/* Make sure sge producer is updated first */
+		dma_wmb();
+		srq->hw_srq.virt_prod_pair_addr->wqe_prod = hw_srq->wqe_prod;
 
-		/* Flush producer after updating it. */
-		wmb();
 		wr = wr->next;
 	}
 
@@ -4182,7 +4181,7 @@ static int process_resp_one_srq(struct qedr_dev *dev, struct qedr_qp *qp,
 	} else {
 		__process_resp_one(dev, qp, cq, wc, resp, wr_id);
 	}
-	srq->hw_srq.wr_cons_cnt++;
+	atomic_inc(&srq->hw_srq.wr_cons_cnt);
 
 	return 1;
 }
-- 
1.8.3.1

Re: [PATCH v3 rdma-next] RDMA/qedr: SRQ's bug fixes

[Jason Gunthorpe]

On Wed, Jul 08, 2020 at 10:55:26PM +0300, Yuval Basson wrote:
> QP's with the same SRQ, working on different CQs and running in parallel
> on different CPUs could lead to a race when maintaining the SRQ consumer
> count, and leads to FW running out of SRQs. Update the consumer atomically.
> Make sure the wqe_prod is updated after the sge_prod due to FW
> requirements.
> 
> Fixes: 3491c9e799fb9 ("RDMA/qedr: Add support for kernel mode SRQ's")
> Signed-off-by: Michal Kalderon <mkalderon@marvell.com>
> Signed-off-by: Yuval Basson <ybason@marvell.com>
> ---
> Change in v3:
>  *Replace changelog
> 
> Changes in v2:
> * Change barrier() to dma_wmb()
> * Remove redundant dma_wmb()
> 
>  drivers/infiniband/hw/qedr/qedr.h  |  4 ++--
>  drivers/infiniband/hw/qedr/verbs.c | 23 +++++++++++------------
>  2 files changed, 13 insertions(+), 14 deletions(-)

Applied to for-next, thanks
  
> diff --git a/drivers/infiniband/hw/qedr/verbs.c b/drivers/infiniband/hw/qedr/verbs.c
> index 9b9e802..444537b 100644
> --- a/drivers/infiniband/hw/qedr/verbs.c
> +++ b/drivers/infiniband/hw/qedr/verbs.c
> @@ -1510,6 +1510,7 @@ int qedr_create_srq(struct ib_srq *ibsrq, struct ib_srq_init_attr *init_attr,
>  	srq->dev = dev;
>  	hw_srq = &srq->hw_srq;
>  	spin_lock_init(&srq->lock);
> +	atomic_set(&hw_srq->wr_cons_cnt, 0);

I deleted this though, it is redundant the memory is pre-zero'd by the
core code.

Jason