Issue: when using virtio nic to transmit pkts, it causes segment fault.
How to reproduce:
Basically, we need to construct a case with vm send packets to vhost-user,
and this issue does not happen when transmitting packets using indirect
desc. Besides, make sure all descriptors are exhausted before vhost
dequeues any packets.
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, just
make sure mrg_rxbuf is enabled.
c. enable testpmd on the host.
testpmd> set fwd io
testpmd> start (better without start vhost-user)
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 (), not necessary to update after
the loop. (And if we do that after the loop, if all descs could have run out,
idx is VQ_RING_DESC_CHAIN_END (32768), use this idx to reference the start_dp
array will lead to segment fault.)
Fixes: dd856dfcb9e ("virtio: use any layout on Tx")
Signed-off-by: Jianfeng Tan <jianfeng.tan at intel.com>
---
v2: refine the commit message.
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;
--
2.1.4
