RDMA/siw: Change CQ flags from 64->32 bits

This patch changes the driver/user shared (mmapped) CQ notification
flags field from unsigned 64-bits size to unsigned 32-bits size. This
enables building siw on 32-bit architectures.

This patch changes the siw-abi, but as siw was only just merged in
this merge window cycle, there are no released kernels with the prior
abi.  We are making no attempt to be binary compatible with siw user
space libraries prior to the merge of siw into the upstream kernel,
only moving forward with upstream kernels and upstream rdma-core
provided siw libraries are we guaranteeing compatibility.

Signed-off-by: Bernard Metzler <bmt@zurich.ibm.com>
Link: https://lore.kernel.org/r/20190809151816.13018-1-bmt@zurich.ibm.com
Signed-off-by: Doug Ledford <dledford@redhat.com>

4 files changed, 23 insertions, 11 deletions

diff --git a/drivers/infiniband/sw/siw/Kconfig b/drivers/infiniband/sw/siw/Kconfig
index dace276aea14..b622fc62f2cd 100644
--- a/drivers/infiniband/sw/siw/Kconfig
+++ b/drivers/infiniband/sw/siw/Kconfig
@@ -1,6 +1,6 @@
 config RDMA_SIW
 	tristate "Software RDMA over TCP/IP (iWARP) driver"
-	depends on INET && INFINIBAND && LIBCRC32C && 64BIT
+	depends on INET && INFINIBAND && LIBCRC32C
 	select DMA_VIRT_OPS
 	help
 	This driver implements the iWARP RDMA transport over
diff --git a/drivers/infiniband/sw/siw/siw.h b/drivers/infiniband/sw/siw/siw.h
index 03fd7b2f595f..77b1aabf6ff3 100644
--- a/drivers/infiniband/sw/siw/siw.h
+++ b/drivers/infiniband/sw/siw/siw.h
@@ -214,7 +214,7 @@ struct siw_wqe {
 struct siw_cq {
 	struct ib_cq base_cq;
 	spinlock_t lock;
-	u64 *notify;
+	struct siw_cq_ctrl *notify;
 	struct siw_cqe *queue;
 	u32 cq_put;
 	u32 cq_get;
diff --git a/drivers/infiniband/sw/siw/siw_qp.c b/drivers/infiniband/sw/siw/siw_qp.c
index e27bd5b35b96..0990307c5d2c 100644
--- a/drivers/infiniband/sw/siw/siw_qp.c
+++ b/drivers/infiniband/sw/siw/siw_qp.c
@@ -1013,18 +1013,24 @@ out:
  */
 static bool siw_cq_notify_now(struct siw_cq *cq, u32 flags)
 {
-	u64 cq_notify;
+	u32 cq_notify;
 
 	if (!cq->base_cq.comp_handler)
 		return false;
 
-	cq_notify = READ_ONCE(*cq->notify);
+	/* Read application shared notification state */
+	cq_notify = READ_ONCE(cq->notify->flags);
 
 	if ((cq_notify & SIW_NOTIFY_NEXT_COMPLETION) ||
 	    ((cq_notify & SIW_NOTIFY_SOLICITED) &&
 	     (flags & SIW_WQE_SOLICITED))) {
-		/* dis-arm CQ */
-		smp_store_mb(*cq->notify, SIW_NOTIFY_NOT);
+		/*
+		 * CQ notification is one-shot: Since the
+		 * current CQE causes user notification,
+		 * the CQ gets dis-aremd and must be re-aremd
+		 * by the user for a new notification.
+		 */
+		WRITE_ONCE(cq->notify->flags, SIW_NOTIFY_NOT);
 
 		return true;
 	}
diff --git a/drivers/infiniband/sw/siw/siw_verbs.c b/drivers/infiniband/sw/siw/siw_verbs.c
index 32dc79d0e898..e7f3a2379d9d 100644
--- a/drivers/infiniband/sw/siw/siw_verbs.c
+++ b/drivers/infiniband/sw/siw/siw_verbs.c
@@ -1049,7 +1049,7 @@ int siw_create_cq(struct ib_cq *base_cq, const struct ib_cq_init_attr *attr,
 
 	spin_lock_init(&cq->lock);
 
-	cq->notify = &((struct siw_cq_ctrl *)&cq->queue[size])->notify;
+	cq->notify = (struct siw_cq_ctrl *)&cq->queue[size];
 
 	if (udata) {
 		struct siw_uresp_create_cq uresp = {};
@@ -1141,11 +1141,17 @@ int siw_req_notify_cq(struct ib_cq *base_cq, enum ib_cq_notify_flags flags)
 	siw_dbg_cq(cq, "flags: 0x%02x\n", flags);
 
 	if ((flags & IB_CQ_SOLICITED_MASK) == IB_CQ_SOLICITED)
-		/* CQ event for next solicited completion */
-		smp_store_mb(*cq->notify, SIW_NOTIFY_SOLICITED);
+		/*
+		 * Enable CQ event for next solicited completion.
+		 * and make it visible to all associated producers.
+		 */
+		smp_store_mb(cq->notify->flags, SIW_NOTIFY_SOLICITED);
 	else
-		/* CQ event for any signalled completion */
-		smp_store_mb(*cq->notify, SIW_NOTIFY_ALL);
+		/*
+		 * Enable CQ event for any signalled completion.
+		 * and make it visible to all associated producers.
+		 */
+		smp_store_mb(cq->notify->flags, SIW_NOTIFY_ALL);
 
 	if (flags & IB_CQ_REPORT_MISSED_EVENTS)
 		return cq->cq_put - cq->cq_get;