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Mon, 25 Apr 2016 15:33:40 +0800
From: "Xie, Huawei" <huawei.xie@intel.com>
To: "Tan, Jianfeng" <jianfeng.tan@intel.com>, "dev@dpdk.org" <dev@dpdk.org>
CC: "yuanhan.liu@linux.intel.com" <yuanhan.liu@linux.intel.com>, "Stephen
Hemminger" <stephen@networkplumber.org>
Thread-Topic: [PATCH v2] virtio: fix segfault when transmit pkts
Thread-Index: AdGexMlnk4tr0GkvWUC33ZQUXpHbnw==
Date: Mon, 25 Apr 2016 07:33:40 +0000
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References: <1461242170-146337-1-git-send-email-jianfeng.tan@intel.com>
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Subject: Re: [dpdk-dev] [PATCH v2] virtio: fix segfault when transmit pkts
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On 4/25/2016 10:37 AM, Tan, Jianfeng wrote:=0A=
> Issue: when using virtio nic to transmit pkts, it causes segment fault.=
=0A=
>=0A=
> How to reproduce:=0A=
> Basically, we need to construct a case with vm send packets to vhost-user=
,=0A=
> and this issue does not happen when transmitting packets using indirect=
=0A=
> desc. Besides, make sure all descriptors are exhausted before vhost=0A=
> dequeues any packets.=0A=
>=0A=
> a. start testpmd with vhost.=0A=
> $ testpmd -c 0x3 -n 4 --socket-mem 1024,0 --no-pci \=0A=
> --vdev 'eth_vhost0,iface=3D/tmp/sock0,queues=3D1' -- -i --nb-cores=3D=
1=0A=
>=0A=
> b. start a qemu with a virtio nic connected with the vhost-user port, jus=
t=0A=
> make sure mrg_rxbuf is enabled.=0A=
>=0A=
> c. enable testpmd on the host.=0A=
> testpmd> set fwd io=0A=
> testpmd> start (better without start vhost-user)=0A=
>=0A=
> d. start testpmd in VM.=0A=
> $testpmd -c 0x3 -n 4 -m 1024 -- -i --disable-hw-vlan-filter --txqflags=
=3D0xf01=0A=
> testpmd> set fwd txonly=0A=
> testpmd> start=0A=
>=0A=
> How to fix: this bug is because inside virtqueue_enqueue_xmit(), the flag=
of=0A=
> desc has been updated inside the do {} while (), not necessary to update =
after=0A=
> the loop. (And if we do that after the loop, if all descs could have run =
out,=0A=
> idx is VQ_RING_DESC_CHAIN_END (32768), use this idx to reference the star=
t_dp=0A=
> array will lead to segment fault.)=0A=
>=0A=
> Fixes: dd856dfcb9e ("virtio: use any layout on Tx")=0A=
>=0A=
> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>=0A=
> ---=0A=
> v2: refine the commit message.=0A=
>=0A=
> drivers/net/virtio/virtio_rxtx.c | 2 --=0A=
> 1 file changed, 2 deletions(-)=0A=
>=0A=
> diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio=
_rxtx.c=0A=
> index ef21d8e..432aeab 100644=0A=
> --- a/drivers/net/virtio/virtio_rxtx.c=0A=
> +++ b/drivers/net/virtio/virtio_rxtx.c=0A=
> @@ -271,8 +271,6 @@ virtqueue_enqueue_xmit(struct virtqueue *txvq, struct=
rte_mbuf *cookie,=0A=
> idx =3D start_dp[idx].next;=0A=
> } while ((cookie =3D cookie->next) !=3D NULL);=0A=
> =0A=
> - start_dp[idx].flags &=3D ~VRING_DESC_F_NEXT;=0A=
> -=0A=
> if (use_indirect)=0A=
> idx =3D txvq->vq_ring.desc[head_idx].next;=0A=
> =0A=
=0A=
Ack the code.=0A=
=0A=
Acked-by: Huawei Xie <huawei.xie@intel.com>=0A=