Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751188AbdFAX4I (ORCPT ); Thu, 1 Jun 2017 19:56:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58276 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751105AbdFAX4G (ORCPT ); Thu, 1 Jun 2017 19:56:06 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com CE8743DE3D Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=mst@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com CE8743DE3D Date: Fri, 2 Jun 2017 02:56:04 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Mikulas Patocka , "J. Bruce Fields" , Jason Wang , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH] virtio_net: lower limit on buffer size Message-ID: <1496361148-4603-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mutt-Fcc: =sent X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 01 Jun 2017 23:56:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 46 commit d85b758f72b0 "virtio_net: fix support for small rings" was supposed to increase the buffer size for small rings but had an unintentional side effect of decreasing it for large rings. This seems to break some setups - it's not yet clear why, but increasing buffer size back to what it was before helps. Fixes: d85b758f72b0 "virtio_net: fix support for small rings" Reported-by: Mikulas Patocka Reported-by: "J. Bruce Fields" Signed-off-by: Michael S. Tsirkin --- Can reporters please confirm whether the following helps? If it does I think we should queue it even though I expect I'll need to investigate the exact reasons for the failure down the road - probably a hypervisor bug. drivers/net/virtio_net.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 87b5c20..60abb5d 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -842,7 +842,7 @@ static unsigned int get_mergeable_buf_len(struct receive_queue *rq, unsigned int len; len = hdr_len + clamp_t(unsigned int, ewma_pkt_len_read(avg_pkt_len), - rq->min_buf_len - hdr_len, PAGE_SIZE - hdr_len); + rq->min_buf_len, PAGE_SIZE - hdr_len); return ALIGN(len, L1_CACHE_BYTES); } @@ -2039,7 +2039,8 @@ static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct virtqu unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len; unsigned int min_buf_len = DIV_ROUND_UP(buf_len, rq_size); - return max(min_buf_len, hdr_len); + return max(max(min_buf_len, hdr_len) - hdr_len, + (unsigned int)GOOD_PACKET_LEN); } static int virtnet_find_vqs(struct virtnet_info *vi) -- MST