From patchwork Tue Mar 26 15:20:36 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Henriques X-Patchwork-Id: 231396 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 288A52C00D0 for ; Wed, 27 Mar 2013 02:24:53 +1100 (EST) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1UKVjx-00036a-EN; Tue, 26 Mar 2013 15:24:45 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1UKVjF-0001tk-7X for kernel-team@lists.ubuntu.com; Tue, 26 Mar 2013 15:24:01 +0000 Received: from bl20-143-66.dsl.telepac.pt ([2.81.143.66] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1UKVjF-0004rW-1o; Tue, 26 Mar 2013 15:24:01 +0000 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com 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 Cc: Ben Hutchings X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 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