From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 1B9082E8A for ; Tue, 26 Apr 2016 07:08:20 +0200 (CEST) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga101.jf.intel.com with ESMTP; 25 Apr 2016 22:08:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,535,1455004800"; d="scan'208";a="91936272" Received: from shwdeisgchi083.ccr.corp.intel.com (HELO [10.239.67.193]) ([10.239.67.193]) by fmsmga004.fm.intel.com with ESMTP; 25 Apr 2016 22:08:19 -0700 To: Stephen Hemminger References: <1461242170-146337-1-git-send-email-jianfeng.tan@intel.com> <20160425214842.25df5915@xeon-e3> Cc: dev@dpdk.org, huawei.xie@intel.com, yuanhan.liu@linux.intel.com From: "Tan, Jianfeng" Message-ID: <571EF7C2.7080502@intel.com> Date: Tue, 26 Apr 2016 13:08:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <20160425214842.25df5915@xeon-e3> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH] virtio: fix segfault when transmit pkts X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Apr 2016 05:08:21 -0000 Hi Stephen, On 4/26/2016 12:48 PM, Stephen Hemminger wrote: > On Thu, 21 Apr 2016 12:36:10 +0000 > Jianfeng Tan wrote: > >> Issue: when using virtio nic to transmit pkts, it causes segment fault. >> >> How to reproduce: >> a. start testpmd with vhost. >> $testpmd -c 0x3 -n 4 --socket-mem 1024,0 --no-pci \ >> --vdev 'eth_vhost0,iface=/tmp/sock0,queues=1' -- -i --nb-cores=1 >> b. start a qemu with a virtio nic connected with the vhost-user port. >> $qemu -smp cores=2,sockets=1 -cpu host -enable-kvm vm-0.img -vnc :5 -m 4G \ >> -object memory-backend-file,id=mem,size=4096M,mem-path=,share=on \ >> -numa node,memdev=mem -mem-prealloc \ >> -chardev socket,id=char1,path=$sock_vhost \ >> -netdev type=vhost-user,id=net1,chardev=char1 \ >> -device virtio-net-pci,netdev=net1,mac=00:01:02:03:04:05 >> c. enable testpmd on the host. >> testpmd> set fwd io >> testpmd> start >> d. start testpmd in VM. >> $testpmd -c 0x3 -n 4 -m 1024 -- -i --disable-hw-vlan-filter --txqflags=0xf01 >> testpmd> set fwd txonly >> testpmd> start >> >> How to fix: this bug is because inside virtqueue_enqueue_xmit(), the flag of >> desc has been updated inside the do {} while (); and after the loop, all descs >> could have run out, so idx is VQ_RING_DESC_CHAIN_END (32768), use this idx to >> reference the start_dp array will lead to segment fault. >> >> Signed-off-by: Jianfeng Tan >> --- >> drivers/net/virtio/virtio_rxtx.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c >> index ef21d8e..432aeab 100644 >> --- a/drivers/net/virtio/virtio_rxtx.c >> +++ b/drivers/net/virtio/virtio_rxtx.c >> @@ -271,8 +271,6 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq, struct rte_mbuf *cookie, >> idx = start_dp[idx].next; >> } while ((cookie = cookie->next) != NULL); >> >> - start_dp[idx].flags &= ~VRING_DESC_F_NEXT; >> - >> if (use_indirect) >> idx = txvq->vq_ring.desc[head_idx].next; >> > At this point in the code idx is the index past the current set of ring > descriptors. So yes this is a real bug. > > I think the description meta-data needs work to explain it better. > > Yes, please see v2. Yuanhan gives a hand to refine it already. Thanks, Jianfeng