netdev - [PATCH AUTOSEL 5.5 43/58] ice: Don't allow same value for Rx tail to be written twice

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Message-Id: <20200223022119.707-43-sashal@kernel.org>
Date:   Sat, 22 Feb 2020 21:21:04 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Brett Creeley <brett.creeley@...el.com>,
        Andrew Bowers <andrewx.bowers@...el.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Sasha Levin <sashal@...nel.org>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 43/58] ice: Don't allow same value for Rx tail to be written twice

From: Brett Creeley <brett.creeley@...el.com>

[ Upstream commit 168983a8e19b89efd175661e53faa6246be363a0 ]

Currently we compare the value we are about to write to the Rx tail
register with the previous value of next_to_use. The problem with this
is we only write tail on 8 descriptor boundaries, but next_to_use is
updated whenever we clean Rx descriptors. Fix this by comparing the
value we are about to write to tail with the previously written tail
value. This will prevent duplicate Rx tail bumps.

Signed-off-by: Brett Creeley <brett.creeley@...el.com>
Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
index 35bbc4ff603cd..6da048a6ca7c1 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
@@ -10,7 +10,7 @@
  */
 void ice_release_rx_desc(struct ice_ring *rx_ring, u32 val)
 {
-	u16 prev_ntu = rx_ring->next_to_use;
+	u16 prev_ntu = rx_ring->next_to_use & ~0x7;
 
 	rx_ring->next_to_use = val;
 
-- 
2.20.1