Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753492AbaJ1Nan (ORCPT ); Tue, 28 Oct 2014 09:30:43 -0400 Received: from mail.karo-electronics.de ([81.173.242.67]:64901 "EHLO mail.karo-electronics.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753342AbaJ1Nak convert rfc822-to-8bit (ORCPT ); Tue, 28 Oct 2014 09:30:40 -0400 Date: Tue, 28 Oct 2014 14:30:36 +0100 From: Lothar =?UTF-8?B?V2HDn21hbm4=?= To: David Laight Cc: "netdev@vger.kernel.org" , "David S. Miller" , Russell King , Frank Li , Fabio Estevam , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCHv2 6/6] net: fec: fix regression on i.MX28 introduced by rx_copybreak support Message-ID: <20141028143036.1eb417f3@ipc1.ka-ro> In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1C9E06B0@AcuExch.aculab.com> References: <1414494104-27943-1-git-send-email-LW@KARO-electronics.de> <1414494104-27943-7-git-send-email-LW@KARO-electronics.de> <063D6719AE5E284EB5DD2968C1650D6D1C9E04C0@AcuExch.aculab.com> <20141028133609.2bf6c745@ipc1.ka-ro> <063D6719AE5E284EB5DD2968C1650D6D1C9E06B0@AcuExch.aculab.com> Organization: Ka-Ro electronics GmbH X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, David Laight wrote: > From: Lothar Waßmann > > David Laight wrote: > > > From: Lothar Waßmann > > > > commit 1b7bde6d659d ("net: fec: implement rx_copybreak to improve rx performance") > > > > introduced a regression for i.MX28. The swap_buffer() function doing > > > > the endian conversion of the received data on i.MX28 may access memory > > > > beyond the actual packet size in the DMA buffer. fec_enet_copybreak() > > > > does not copy those bytes, so that the last bytes of a packet may be > > > > filled with invalid data after swapping. > > > > This will likely lead to checksum errors on received packets. > > > > E.g. when trying to mount an NFS rootfs: > > > > UDP: bad checksum. From 192.168.1.225:111 to 192.168.100.73:44662 ulen 36 > > > > > > > > Do the byte swapping and copying to the new skb in one go if > > > > necessary. > > > > > > > > Signed-off-by: Lothar Wamann > > > > --- > > > > drivers/net/ethernet/freescale/fec_main.c | 25 +++++++++++++++++++++---- > > > > 1 file changed, 21 insertions(+), 4 deletions(-) > > > > > > > > @@ -1455,7 +1472,7 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id) > > > > prefetch(skb->data - NET_IP_ALIGN); > > > > skb_put(skb, pkt_len - 4); > > > > data = skb->data; > > > > - if (fep->quirks & FEC_QUIRK_SWAP_FRAME) > > > > + if (!is_copybreak && need_swap) > > > > swap_buffer(data, pkt_len); > > > > > > It has to be better to set the 'copybreak' limit to be larger than the > > > maximum frame size and so always go through the 'copybreak' paths. > > > > > Since the copybreak support is all about performance optimistation, we > > should IMO buy the additional advantage for i.MX28 by not having to > > access the buffer twice (once for copying and once again for swapping). > > You definitely want to do the byteswap at the same time as the copy. > > The point I'm trying to make that if you need to do the byteswap you > probably might as well copy the data to an skb of the correct size at > the same time. > Certainly I'd expect the 'break even' length will be much higher. > I didn't implement the copybreak support. I'm only trying to fix a bug it introduced for i.MX28. So, I won't mess with the copybreak parameters. Lothar Waßmann -- ___________________________________________________________ Ka-Ro electronics GmbH | Pascalstraße 22 | D - 52076 Aachen Phone: +49 2408 1402-0 | Fax: +49 2408 1402-10 Geschäftsführer: Matthias Kaussen Handelsregistereintrag: Amtsgericht Aachen, HRB 4996 www.karo-electronics.de | info@karo-electronics.de ___________________________________________________________ -- 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/