From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tom Lendacky Subject: [PATCH net-next v1 1/8] amd-xgbe: Add a read memory barrier to Tx/Rx path Date: Thu, 20 Nov 2014 11:03:26 -0600 Message-ID: <20141120170326.15397.96332.stgit@tlendack-t1.amdoffice.net> References: <20141120170320.15397.10583.stgit@tlendack-t1.amdoffice.net> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: David Miller To: Return-path: Received: from mail-bn1on0132.outbound.protection.outlook.com ([157.56.110.132]:8096 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756934AbaKTRDd (ORCPT ); Thu, 20 Nov 2014 12:03:33 -0500 In-Reply-To: <20141120170320.15397.10583.stgit@tlendack-t1.amdoffice.net> Sender: netdev-owner@vger.kernel.org List-ID: Add a read memory barrier to the Tx and Rx paths where the ownership bit is checked to be sure that all descriptor fields are read after having read the ownership bit for the descriptor. This has not been an issue to date, but it's a good safe-guard to have. Signed-off-by: Tom Lendacky --- drivers/net/ethernet/amd/xgbe/xgbe-dev.c | 3 +++ drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 4 ++++ 2 files changed, 7 insertions(+) diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c index f6014d3..9b1d9fa 100644 --- a/drivers/net/ethernet/amd/xgbe/xgbe-dev.c +++ b/drivers/net/ethernet/amd/xgbe/xgbe-dev.c @@ -1558,6 +1558,9 @@ static int xgbe_dev_read(struct xgbe_channel *channel) if (XGMAC_GET_BITS_LE(rdesc->desc3, RX_NORMAL_DESC3, OWN)) return 1; + /* Make sure descriptor fields are read after reading the OWN bit */ + rmb(); + #ifdef XGMAC_ENABLE_RX_DESC_DUMP xgbe_dump_rx_desc(ring, rdesc, ring->cur); #endif diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c index 0544931..eebb787 100644 --- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c +++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c @@ -1791,6 +1791,10 @@ static int xgbe_tx_poll(struct xgbe_channel *channel) if (!hw_if->tx_complete(rdesc)) break; + /* Make sure descriptor fields are read after reading the OWN + * bit */ + rmb(); + #ifdef XGMAC_ENABLE_TX_DESC_DUMP xgbe_dump_tx_desc(ring, ring->dirty, 1, 0); #endif