From 94b52958b77a2a040564cf7ed716d3a9545d94e5 Mon Sep 17 00:00:00 2001 From: Greg Kurz Date: Tue, 20 Mar 2018 11:44:56 +0100 Subject: [PATCH] virtio_net: flush uncompleted TX on reset 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 push async_tx.elem back to the guest anyway, and we end up with the inuse flag 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 backend that is not connected to a functional network, eg, -device virtio-net-pci,netdev=hub0 -netdev hubport,id=hub0,hubid=0 and no other -netdev hubport,hubid=0 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. CC: qemu-stable@nongnu.org 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 Signed-off-by: Jason Wang --- hw/net/virtio-net.c | 11 +++++++++++ include/net/net.h | 1 + net/net.c | 1 - 3 files changed, 12 insertions(+), 1 deletion(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 67ad38cfe4..90502fca7c 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -427,6 +427,7 @@ static RxFilterInfo *virtio_net_query_rxfilter(NetClientState *nc) static void virtio_net_reset(VirtIODevice *vdev) { VirtIONet *n = VIRTIO_NET(vdev); + int i; /* Reset back to compatibility mode */ n->promisc = 1; @@ -450,6 +451,16 @@ 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 = 0; i < n->max_queues; i++) { + NetClientState *nc = qemu_get_subqueue(n->nic, i); + + if (nc->peer) { + qemu_flush_or_purge_queued_packets(nc->peer, true); + assert(!virtio_net_get_subqueue(nc)->async_tx.elem); + } + } } static void peer_test_vnet_hdr(VirtIONet *n) diff --git a/include/net/net.h b/include/net/net.h index a943e968a3..1f7341e459 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 5222e45069..29f83983e5 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); } -static void qemu_flush_or_purge_queued_packets(NetClientState *nc, bool purge) { nc->receive_disabled = 0;