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 041B8298F for ; Mon, 25 Apr 2016 03:58:26 +0200 (CEST) Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga101.jf.intel.com with ESMTP; 24 Apr 2016 18:58:25 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,530,1455004800"; d="scan'208";a="91173129" Received: from shwdeisgchi083.ccr.corp.intel.com (HELO [10.239.67.193]) ([10.239.67.193]) by fmsmga004.fm.intel.com with ESMTP; 24 Apr 2016 18:58:24 -0700 To: "Xie, Huawei" , Yuanhan Liu References: <1461242170-146337-1-git-send-email-jianfeng.tan@intel.com> <20160421224444.GC7603@yliu-dev.sh.intel.com> Cc: "dev@dpdk.org" , Stephen Hemminger From: "Tan, Jianfeng" Message-ID: <571D79BF.1090604@intel.com> Date: Mon, 25 Apr 2016 09:58:23 +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: 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: Mon, 25 Apr 2016 01:58:27 -0000 Hi Yuanhan & Huawei, On 4/22/2016 10:23 PM, Xie, Huawei wrote: > On 4/22/2016 6:43 AM, Yuanhan Liu wrote: >> On Thu, Apr 21, 2016 at 12:36:10PM +0000, Jianfeng Tan wrote: >>> Issue: when using virtio nic to transmit pkts, it causes segment fault. >> Jianfeng, >> >> It's good to describe the issues, steps to reproduce it and how to fix >> it. But you don't have to tell it like filling a form. Instead, you >> could try to describe in plain English. >> >>> 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 >> I personally would suggest to add some indentations (and some whitespace >> lines), like >> >> a. start testpmd with vhost. >> $ testpmd -c 0x3 -n 4 ... \ >> --vdev '...' ... >> >> b. something else ... >> some more explanations. >> >> And, do not quote a command line like "$testpmd ...", it's like a var >> in base in this way. Instead, add a space after "$ ", like what I did >> above. >> >>> b. start a qemu with a virtio nic connected with the vhost-user port. >> This should be enough. I didn't find any special options below, >> therefore, above words is enough. However, if it's some specific >> option introduces a bug, you could claim it aloud then. >> >>> $qemu -smp cores=2,sockets=1 -cpu host -enable-kvm vm-0.img -vnc :5 -m 4G \ >>> -object memory-backend-file,id=mem,size=4096M,mem-path=,share=on \ >>> -numa node,memdev=mem -mem-prealloc \ >>> -chardev socket,id=char1,path=$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 > With txqflags=0xf01, virtio PMD will use virtio_xmit_pkts_simple, in > which case the enqueue_xmit willn't called, so typo? Since mrg_rxbuf is by default enabled, so virtio PMD will not use virtio_xmit_pkts_simple. > >>> 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. >> You missed a fix line here. > Yes, please include the commit that introduces this bug. Thanks to both of you for all the advice above. I'll send a v2. > >>> 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; >> This looks a good fix to me. I'm just wondering why we never met it >> before, and on which specific case do we meet it? Talking about that, >> seems like "set fwd txonly" is with high suspicious. > You will not meet this if you have more free descriptors than needed, so > this depends on the relative speed of virtio xmit and vhost dequeue. > Also if indirect feature is negotiated, it willn't trigger. > However, without indirect, seems as long as we start testpmd with txonly > in guest `first`, we could definitely trigger this. Jianfeng, could you > confirm this and emphasize the order in the commit message? Yes, exactly. And will add the scenario description into commit message. Thanks, Jianfeng > >> --yliu >> >