[PATCH for-rc 4/7] IB/hfi1: Use aborts to trigger RC throttling

[Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>]

From: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>

SDMA and pio flushes will cause a lot of packets to be transmitted
after a link has gone down, using a lot of CPU to retransmit
packets.

Fix for RC QPs by recognizing the flush status and:
- Forcing a timer start
- Putting the QP into a "send one" mode

Fixes: 7724105686e7 ("IB/hfi1: add driver files")
Reviewed-by: Kaike Wan <kaike.wan@xxxxxxxxx>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxx>
---
 drivers/infiniband/hw/hfi1/rc.c    |   30 ++++++++++++++++++++++++++++++
 drivers/infiniband/hw/hfi1/verbs.c |   10 ++++++----
 drivers/infiniband/hw/hfi1/verbs.h |    1 +
 3 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/rc.c b/drivers/infiniband/hw/hfi1/rc.c
index 2a7861f..4532d3c 100644
--- a/drivers/infiniband/hw/hfi1/rc.c
+++ b/drivers/infiniband/hw/hfi1/rc.c
@@ -1701,6 +1701,36 @@ static void reset_sending_psn(struct rvt_qp *qp, u32 psn)
 	}
 }
 
+/**
+ * hfi1_rc_verbs_aborted - handle abort status
+ * @qp: the QP
+ * @opah: the opa header
+ *
+ * This code modifies both ACK bit in BTH[2]
+ * and the s_flags to go into send one mode.
+ *
+ * This serves to throttle the send engine to only
+ * send a single packet in the likely case the
+ * a link has gone down.
+ */
+void hfi1_rc_verbs_aborted(struct rvt_qp *qp, struct hfi1_opa_header *opah)
+{
+	struct ib_other_headers *ohdr = hfi1_get_rc_ohdr(opah);
+	u8 opcode = ib_bth_get_opcode(ohdr);
+	u32 psn;
+
+	/* ignore responses */
+	if ((opcode >= OP(RDMA_READ_RESPONSE_FIRST) &&
+	     opcode <= OP(ATOMIC_ACKNOWLEDGE)) ||
+	    opcode == TID_OP(READ_RESP) ||
+	    opcode == TID_OP(WRITE_RESP))
+		return;
+
+	psn = ib_bth_get_psn(ohdr) | IB_BTH_REQ_ACK;
+	ohdr->bth[2] = cpu_to_be32(psn);
+	qp->s_flags |= RVT_S_SEND_ONE;
+}
+
 /*
  * This should be called with the QP s_lock held and interrupts disabled.
  */
diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
index 1eb4105..1241ea6 100644
--- a/drivers/infiniband/hw/hfi1/verbs.c
+++ b/drivers/infiniband/hw/hfi1/verbs.c
@@ -638,6 +638,8 @@ static void verbs_sdma_complete(
 		struct hfi1_opa_header *hdr;
 
 		hdr = &tx->phdr.hdr;
+		if (unlikely(status == SDMA_TXREQ_S_ABORTED))
+			hfi1_rc_verbs_aborted(qp, hdr);
 		hfi1_rc_send_complete(qp, hdr);
 	}
 	spin_unlock(&qp->s_lock);
@@ -1095,15 +1097,15 @@ int hfi1_verbs_send_pio(struct rvt_qp *qp, struct hfi1_pkt_state *ps,
 			       &ps->s_txreq->phdr.hdr, ib_is_sc5(sc5));
 
 pio_bail:
+	spin_lock_irqsave(&qp->s_lock, flags);
 	if (qp->s_wqe) {
-		spin_lock_irqsave(&qp->s_lock, flags);
 		rvt_send_complete(qp, qp->s_wqe, wc_status);
-		spin_unlock_irqrestore(&qp->s_lock, flags);
 	} else if (qp->ibqp.qp_type == IB_QPT_RC) {
-		spin_lock_irqsave(&qp->s_lock, flags);
+		if (unlikely(wc_status == IB_WC_GENERAL_ERR))
+			hfi1_rc_verbs_aborted(qp, &ps->s_txreq->phdr.hdr);
 		hfi1_rc_send_complete(qp, &ps->s_txreq->phdr.hdr);
-		spin_unlock_irqrestore(&qp->s_lock, flags);
 	}
+	spin_unlock_irqrestore(&qp->s_lock, flags);
 
 	ret = 0;
 
diff --git a/drivers/infiniband/hw/hfi1/verbs.h b/drivers/infiniband/hw/hfi1/verbs.h
index 7ecb8ed..ae9582d 100644
--- a/drivers/infiniband/hw/hfi1/verbs.h
+++ b/drivers/infiniband/hw/hfi1/verbs.h
@@ -416,6 +416,7 @@ void hfi1_rc_hdrerr(
 
 u8 ah_to_sc(struct ib_device *ibdev, struct rdma_ah_attr *ah_attr);
 
+void hfi1_rc_verbs_aborted(struct rvt_qp *qp, struct hfi1_opa_header *opah);
 void hfi1_rc_send_complete(struct rvt_qp *qp, struct hfi1_opa_header *opah);
 
 void hfi1_ud_rcv(struct hfi1_packet *packet);