Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934824Ab3CZPaA (ORCPT ); Tue, 26 Mar 2013 11:30:00 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54160 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965415Ab3CZPYC (ORCPT ); Tue, 26 Mar 2013 11:24:02 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Ben Hutchings , Luis Henriques Subject: [PATCH 137/150] sfc: Only use TX push if a single descriptor is to be written Date: Tue, 26 Mar 2013 15:20:36 +0000 Message-Id: <1364311249-14454-138-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1364311249-14454-1-git-send-email-luis.henriques@canonical.com> References: <1364311249-14454-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1723 Lines: 45 3.5.7.9 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Ben Hutchings commit fae8563b25f73dc584a07bcda7a82750ff4f7672 upstream. Using TX push when notifying the NIC of multiple new descriptors in the ring will very occasionally cause the TX DMA engine to re-use an old descriptor. This can result in a duplicated or partly duplicated packet (new headers with old data), or an IOMMU page fault. This does not happen when the pushed descriptor is the only one written. TX push also provides little latency benefit when a packet requires more than one descriptor. Signed-off-by: Ben Hutchings Signed-off-by: Luis Henriques --- drivers/net/ethernet/sfc/nic.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/sfc/nic.c b/drivers/net/ethernet/sfc/nic.c index 76f16b7..578e52a6 100644 --- a/drivers/net/ethernet/sfc/nic.c +++ b/drivers/net/ethernet/sfc/nic.c @@ -379,7 +379,8 @@ efx_may_push_tx_desc(struct efx_tx_queue *tx_queue, unsigned int write_count) return false; tx_queue->empty_read_count = 0; - return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0; + return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0 + && tx_queue->write_count - write_count == 1; } /* For each entry inserted into the software descriptor ring, create a -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/