[PATCH][focal:linux-azure] net: mana: Add rmb after checking owner bits

[Tim Gardner]

From: Haiyang Zhang <haiyangz at microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/1994987

commit 6fd2c68da55c552f86e401ebe40c4a619025ef69 upstream.

Per GDMA spec, rmb is necessary after checking owner_bits, before
reading EQ or CQ entries.

Add rmb in these two places to comply with the specs.

Cc: stable at vger.kernel.org
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Reported-by: Sinan Kaya <Sinan.Kaya at microsoft.com>
Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
Reviewed-by: Dexuan Cui <decui at microsoft.com>
Link: https://lore.kernel.org/r/1662928805-15861-1-git-send-email-haiyangz@microsoft.com
Signed-off-by: Jakub Kicinski <kuba at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit 71075d7d463281fd43cebf3a10170503a1c72995 linux-5.15.y)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 drivers/net/ethernet/microsoft/mana/gdma_main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/microsoft/mana/gdma_main.c b/drivers/net/ethernet/microsoft/mana/gdma_main.c
index 2f87bf90f8ec..6308ed90b60d 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -365,6 +365,11 @@ static void mana_gd_process_eq_events(void *arg)
 			break;
 		}
 
+		/* Per GDMA spec, rmb is necessary after checking owner_bits, before
+		 * reading eqe.
+		 */
+		rmb();
+
 		mana_gd_process_eqe(eq);
 
 		eq->head++;
@@ -1131,6 +1136,11 @@ static int mana_gd_read_cqe(struct gdma_queue *cq, struct gdma_comp *comp)
 	if (owner_bits != new_bits)
 		return -1;
 
+	/* Per GDMA spec, rmb is necessary after checking owner_bits, before
+	 * reading completion info
+	 */
+	rmb();
+
 	comp->wq_num = cqe->cqe_info.wq_num;
 	comp->is_sq = cqe->cqe_info.is_sq;
 	memcpy(comp->cqe_data, cqe->cqe_data, GDMA_COMP_DATA_SIZE);
-- 
2.34.1