From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752772AbaBMDCc (ORCPT ); Wed, 12 Feb 2014 22:02:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:6972 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752619AbaBMDC1 (ORCPT ); Wed, 12 Feb 2014 22:02:27 -0500 Message-ID: <52FC35B5.6000900@redhat.com> Date: Thu, 13 Feb 2014 11:02:13 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: rusty@rustcorp.com.au, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Sridhar Samudrala Subject: Re: [PATCH net] virtio-net: alloc big buffers also when guest can receive UFO References: <1392183808-16789-1-git-send-email-jasowang@redhat.com> <20140212115901.GC23006@redhat.com> In-Reply-To: <20140212115901.GC23006@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/12/2014 07:59 PM, Michael S. Tsirkin wrote: > On Wed, Feb 12, 2014 at 01:43:28PM +0800, Jason Wang wrote: >> > We should alloc big buffers also when guest can receive UFO >> > pakcets. Otherwise the big packets will be truncated when mergeable rx >> > buffer is disabled. > Not truncated, they will be dropped. > Why dropped? We enable the ufo on tap0 if VIRTIO_NET_F_GUEST_UFO is negotiated. So skb was queued on the receive queue. But since the receive buffer is small, it will be truncated during tun_put_user().