[PATCH] e1000e: Disable TSO for buffer overrun workaround

Commit b10effb92e27 ("e1000e: fix buffer overrun while the I219 is
processing DMA transactions") imposes roughly 30% performance penalty.

The commit log states that "Disabling TSO eliminates performance loss
for TCP traffic without a noticeable impact on CPU performance", so
let's disable TSO by default to regain the loss.

Fixes: b10effb92e27 ("e1000e: fix buffer overrun while the I219 is processing DMA transactions")
BugLink: https://bugs.launchpad.net/bugs/1802691
Signed-off-by: Kai-Heng Feng <redacted>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 177c6da80c57..9b5509149578 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c

@@ -5294,6 +5294,10 @@ static void e1000_watchdog_task(struct work_struct *work)
 					/* oops */
 					break;
 				}
+				if (hw->mac.type == e1000_pch_spt) {
+					netdev->features &= ~NETIF_F_TSO;
+					netdev->features &= ~NETIF_F_TSO6;
+				}
 			}
 
 			/* enable transmits in the hardware, need to do this

-- 
2.17.1

From: netdev-owner@vger.kernel.org <redacted> On
Behalf Of Kai-Heng Feng
Sent: Thursday, May 7, 2020 7:21 AM
To: Kirsher, Jeffrey T <redacted>
Cc: Kai-Heng Feng <redacted>; David S. Miller
[off-list ref]; Neftin, Sasha [off-list ref]; Dima
Ruinskiy [off-list ref]; Avargil, Raanan
[off-list ref]; moderated list:INTEL ETHERNET DRIVERS <intel-
wired-lan@lists.osuosl.org>; open list:NETWORKING DRIVERS
[off-list ref]; open list [off-list ref]
Subject: [PATCH] e1000e: Disable TSO for buffer overrun workaround

Commit b10effb92e27 ("e1000e: fix buffer overrun while the I219 is
processing DMA transactions") imposes roughly 30% performance penalty.

The commit log states that "Disabling TSO eliminates performance loss
for TCP traffic without a noticeable impact on CPU performance", so
let's disable TSO by default to regain the loss.

Fixes: b10effb92e27 ("e1000e: fix buffer overrun while the I219 is processing
DMA transactions")
BugLink: https://bugs.launchpad.net/bugs/1802691
Signed-off-by: Kai-Heng Feng <redacted>
---
 drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++++
 1 file changed, 4 insertions(+)

Tested-by: Aaron Brown <redacted>