From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966887AbeCAJXv (ORCPT ); Thu, 1 Mar 2018 04:23:51 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54768 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965026AbeCAJXq (ORCPT ); Thu, 1 Mar 2018 04:23:46 -0500 Subject: Re: [PATCH net-next 0/2] virtio-net: re enable XDP_REDIRECT for mergeable buffer To: Jesper Dangaard Brouer Cc: mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, john.fastabend@gmail.com References: <1519874345-10235-1-git-send-email-jasowang@redhat.com> <20180301101038.4253424d@redhat.com> From: Jason Wang Message-ID: Date: Thu, 1 Mar 2018 17:23:37 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180301101038.4253424d@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018年03月01日 17:10, Jesper Dangaard Brouer wrote: > On Thu, 1 Mar 2018 11:19:03 +0800 > Jason Wang wrote: > >> This series tries to re-enable XDP_REDIRECT for mergeable buffer which >> was removed since commit 7324f5399b06 ("virtio_net: disable >> XDP_REDIRECT in receive_mergeable() case"). Main concerns are: >> >> - not enough tailroom was reserved which breaks cpumap > To address this at a more fundamental level, I would suggest that we/you > instead extend XDP to know it's buffers "frame" size/end. (The > assumption use to be, xdp_buff->data_hard_start + PAGE_SIZE, but > ixgbe+virtio_net broke that assumption). > > It should actually be fairly easy to implement: > * Simply extend xdp_buff with a "data_hard_end" pointer. Right, and then cpumap can warn and drop packets with insufficient tailroom. But it should be a patch on top of this I think. Thanks > > Now cpumap is more safe... instead of crashing, it can now know/see when > it is safe to create an SKB using build_skb (could fallback to > dev_alloc_skb). >