netdev - [PATCH net] net: mana: Add rmb after checking owner bits

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Message-Id: <1662928805-15861-1-git-send-email-haiyangz@microsoft.com>
Date:   Sun, 11 Sep 2022 13:40:05 -0700
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     linux-hyperv@...r.kernel.org, netdev@...r.kernel.org
Cc:     haiyangz@...rosoft.com, decui@...rosoft.com, kys@...rosoft.com,
        sthemmin@...rosoft.com, paulros@...rosoft.com,
        shacharr@...rosoft.com, olaf@...fle.de, vkuznets@...hat.com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: [PATCH net] net: mana: Add rmb after checking owner bits

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@...r.kernel.org
Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
Reported-by: Sinan Kaya <Sinan.Kaya@...rosoft.com>
Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.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 5f9240182351..e10b9f8f89e1 100644
--- a/drivers/net/ethernet/microsoft/mana/gdma_main.c
+++ b/drivers/net/ethernet/microsoft/mana/gdma_main.c
@@ -397,6 +397,11 @@ 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++;
@@ -1134,6 +1139,11 @@ static int mana_gd_read_cqe(struct gdma_queue *cq, struct gdma_comp *comp)
 	if (WARN_ON_ONCE(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);
-- 
2.25.1