Ping ? On Thu, 8 Mar 2018 10:38:56 +0530 "Nageswara R Sastry" <nasas...@in.ibm.com> wrote:
> Greg Kurz <gr...@kaod.org> wrote on 08/03/2018 12:27:37 AM: > > > From: Greg Kurz <gr...@kaod.org> > > To: qemu-devel@nongnu.org > > Cc: "Michael S. Tsirkin" <m...@redhat.com>, Jason Wang > > <jasow...@redhat.com>, R Nageswara Sastry <nasas...@in.ibm.com> > > Date: 08/03/2018 12:27 AM > > 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 without a net backend, > > doing a system reset when it is booted, and finally snapshotting it. > > > > 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 <nasas...@in.ibm.com> > > Tested-by: R. Nageswara Sastry <nasas...@in.ibm.com> > > > Buglink: https://urldefense.proofpoint.com/v2/url? > > > u=https-3A__github.com_open-2Dpower-2Dhost-2Dos_qemu_issues_37&d=DwICaQ&c=jf_iaSHvJObTbx- > > siA1ZOg&r=mxAxqGE8eb0FlPPFjDZkTNaoci-GdQbkJayE4r- > > > wzYY&m=hPoY6b601IXJbUV2uh22jBrnYuByNQpwi1d7gvN4yZs&s=Ic3NN3mM_Nv1gAJ7dY22- > > ebnJsG7c0yNkbThX8Tu6xg&e= > > Signed-off-by: Greg Kurz <gr...@kaod.org> > > --- > > hw/net/virtio-net.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > index 188744e17d57..eea3cdb2c700 100644 > > --- a/hw/net/virtio-net.c > > +++ b/hw/net/virtio-net.c > > @@ -422,6 +422,7 @@ 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; > > @@ -445,6 +446,16 @@ 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 (!qemu_net_queue_flush(nc->peer->incoming_queue)) { > > + qemu_net_queue_purge(nc->peer->incoming_queue, nc); > > + } > > + assert(!virtio_net_get_subqueue(nc)->async_tx.elem); > > + } > > } > > > > static void peer_test_vnet_hdr(VirtIONet *n) > > > > > With out patch: > (qemu) system_reset > (qemu) savevm 1 > Virtqueue size exceeded > (qemu) loadvm 1 > VQ 1 size 0x100 < last_avail_idx 0x0 - used_idx 0x1 > Failed to load virtio-net:virtio > error while loading state for instance 0x0 of device > 'pci@800000020000000:00.0/virtio-net' > Error -1 while loading VM state > > With patch: > (qemu) system_reset > (qemu) savevm 1 > (qemu) loadvm 1 > > > >
