See also https://issues.redhat.com/browse/RHEL-1303 On Mon, Jan 15, 2024 at 9:48 PM Andrew Melnychenko <andrew@xxxxxxxxxx> wrote: > > When the Qemu launched with vhost but without tap vnet_hdr, > vhost tries to copy vnet_hdr from socket iter with size 0 > to the page that may contain some trash. > That trash can be interpreted as unpredictable values for > vnet_hdr. > That leads to dropping some packets and in some cases to > stalling vhost routine when the vhost_net tries to process > packets and fails in a loop. > > Qemu options: > -netdev tap,vhost=on,vnet_hdr=off,... > > Signed-off-by: Andrew Melnychenko <andrew@xxxxxxxxxx> > --- > drivers/vhost/net.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c > index f2ed7167c848..57411ac2d08b 100644 > --- a/drivers/vhost/net.c > +++ b/drivers/vhost/net.c > @@ -735,6 +735,9 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq, > hdr = buf; > gso = &hdr->gso; > > + if (!sock_hlen) > + memset(buf, 0, pad); > + > if ((gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) && > vhost16_to_cpu(vq, gso->csum_start) + > vhost16_to_cpu(vq, gso->csum_offset) + 2 > > -- > 2.43.0 >
