From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40748) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ey76e-0001Nd-10 for qemu-devel@nongnu.org; Mon, 19 Mar 2018 22:34:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ey76a-0006yh-Qx for qemu-devel@nongnu.org; Mon, 19 Mar 2018 22:34:32 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50592 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ey76a-0006pr-Lt for qemu-devel@nongnu.org; Mon, 19 Mar 2018 22:34:28 -0400 References: <152120204902.1103.7114773412109402452.stgit@bahia.lan> From: Jason Wang Message-ID: <181e938f-76b7-84b2-96f1-1f8832236e23@redhat.com> Date: Tue, 20 Mar 2018 10:34:09 +0800 MIME-Version: 1.0 In-Reply-To: <152120204902.1103.7114773412109402452.stgit@bahia.lan> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] virtio_net: flush uncompleted TX on reset List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz , qemu-devel@nongnu.org Cc: R Nageswara Sastry , "Michael S. Tsirkin" On 2018=E5=B9=B403=E6=9C=8816=E6=97=A5 20:07, Greg Kurz wrote: > If the backend could not transmit a packet right away for some reason, > the packet is queued for asynchronous sending. The corresponding vq > element is tracked in the async_tx.elem field of the VirtIONetQueue, > for later freeing when the transmission is complete. > > If a reset happens before completion, virtio_net_tx_complete() will pus= h > async_tx.elem back to the guest anyway, and we end up with the inuse fl= ag > of the vq being equal to -1. The next call to virtqueue_pop() is then > likely to fail with "Virtqueue size exceeded". > > This can be reproduced easily by starting a guest with an hubport backe= nd > that is not connected to a functional network, eg, > > -device virtio-net-pci,netdev=3Dhub0 -netdev hubport,id=3Dhub0,hubid=3D= 0 > > and no other -netdev hubport,hubid=3D0 on the command line. > > The appropriate fix is to ensure that such an asynchronous transmission > cannot survive a device reset. So for all queues, we first try to send > the packet again, and eventually we purge it if the backend still could > not deliver it. > > Reported-by: R. Nageswara Sastry > Buglink: https://github.com/open-power-host-os/qemu/issues/37 > Signed-off-by: Greg Kurz > Tested-by: R. Nageswara Sastry > --- > v2: - make qemu_flush_or_purge_queued_packets() extern and use it > - reworded reproducer paragraph in changelog > --- > hw/net/virtio-net.c | 8 ++++++++ > include/net/net.h | 1 + > net/net.c | 1 - > 3 files changed, 9 insertions(+), 1 deletion(-) > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > index 188744e17d57..e5ed35489380 100644 > --- a/hw/net/virtio-net.c > +++ b/hw/net/virtio-net.c > @@ -422,6 +422,7 @@ static RxFilterInfo *virtio_net_query_rxfilter(NetC= lientState *nc) > static void virtio_net_reset(VirtIODevice *vdev) > { > VirtIONet *n =3D VIRTIO_NET(vdev); > + int i; > =20 > /* Reset back to compatibility mode */ > n->promisc =3D 1; > @@ -445,6 +446,13 @@ static void virtio_net_reset(VirtIODevice *vdev) > memcpy(&n->mac[0], &n->nic->conf->macaddr, sizeof(n->mac)); > qemu_format_nic_info_str(qemu_get_queue(n->nic), n->mac); > memset(n->vlans, 0, MAX_VLAN >> 3); > + > + /* Flush any async TX */ > + for (i =3D 0; i < n->max_queues; i++) { > + NetClientState *nc =3D qemu_get_subqueue(n->nic, i); > + qemu_flush_or_purge_queued_packets(nc->peer, true); > + assert(!virtio_net_get_subqueue(nc)->async_tx.elem); > + } > } > =20 > static void peer_test_vnet_hdr(VirtIONet *n) > diff --git a/include/net/net.h b/include/net/net.h > index a943e968a3dc..1f7341e4592b 100644 > --- a/include/net/net.h > +++ b/include/net/net.h > @@ -153,6 +153,7 @@ ssize_t qemu_send_packet_async(NetClientState *nc, = const uint8_t *buf, > int size, NetPacketSent *sent_cb); > void qemu_purge_queued_packets(NetClientState *nc); > void qemu_flush_queued_packets(NetClientState *nc); > +void qemu_flush_or_purge_queued_packets(NetClientState *nc, bool purge= ); > void qemu_format_nic_info_str(NetClientState *nc, uint8_t macaddr[6])= ; > bool qemu_has_ufo(NetClientState *nc); > bool qemu_has_vnet_hdr(NetClientState *nc); > diff --git a/net/net.c b/net/net.c > index 5222e450698c..29f83983e55d 100644 > --- a/net/net.c > +++ b/net/net.c > @@ -595,7 +595,6 @@ void qemu_purge_queued_packets(NetClientState *nc) > qemu_net_queue_purge(nc->peer->incoming_queue, nc); > } > =20 > -static > void qemu_flush_or_purge_queued_packets(NetClientState *nc, bool purg= e) > { > nc->receive_disabled =3D 0; > > Applied and queued for -stable. Thanks