On Mon, Feb 18, 2019 at 6:39 PM Michael S. Tsirkin <m...@redhat.com> wrote: > > On Mon, Feb 18, 2019 at 11:58:51AM +0200, Yuri Benditovich wrote: > > On Mon, Feb 18, 2019 at 5:49 AM Jason Wang <jasow...@redhat.com> wrote: > > > > > > > > > On 2019/2/13 下午10:51, Yuri Benditovich wrote: > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1608226 > > > > On startup/link-up in multiqueue configuration the virtio-net > > > > tries to starts all the queues, including those that the guest > > > > will not enable by VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET. > > > > If the guest driver does not allocate queues that it will not > > > > use (for example, Windows driver does not) and number of actually > > > > used queues is less that maximal number supported by the device, > > > > > > > > > Is this a requirement of e.g NDIS? If not, could we simply allocate all > > > queues in this case. This is usually what normal Linux driver did. > > > > > > > > > > this causes vhost_net_start to fail and actually disables vhost > > > > for all the queues, reducing the performance. > > > > Current commit fixes this: initially only first queue is started, > > > > upon VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET started all the queues > > > > requested by the guest. > > > > > > > > Signed-off-by: Yuri Benditovich <yuri.benditov...@daynix.com> > > > > --- > > > > hw/net/virtio-net.c | 7 +++++-- > > > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > > > index 3f319ef723..d3b1ac6d3a 100644 > > > > --- a/hw/net/virtio-net.c > > > > +++ b/hw/net/virtio-net.c > > > > @@ -174,7 +174,7 @@ static void virtio_net_vhost_status(VirtIONet *n, > > > > uint8_t status) > > > > { > > > > VirtIODevice *vdev = VIRTIO_DEVICE(n); > > > > NetClientState *nc = qemu_get_queue(n->nic); > > > > - int queues = n->multiqueue ? n->max_queues : 1; > > > > + int queues = n->multiqueue ? n->curr_queues : 1; > > > > > > > > if (!get_vhost_net(nc->peer)) { > > > > return; > > > > @@ -1016,9 +1016,12 @@ static int virtio_net_handle_mq(VirtIONet *n, > > > > uint8_t cmd, > > > > return VIRTIO_NET_ERR; > > > > } > > > > > > > > - n->curr_queues = queues; > > > > /* stop the backend before changing the number of queues to avoid > > > > handling a > > > > * disabled queue */ > > > > + virtio_net_set_status(vdev, 0); > > > > > > > > > Any reason for doing this? > > > > I think there are 2 reasons: > > 1. The spec does not require guest SW to allocate unused queues. > > 2. We spend guest's physical memory to just make vhost happy when it > > touches queues that it should not use. > > > > Thanks, > > Yuri Benditovich > > The spec also says: > queue_enable The driver uses this to selectively prevent the device > from executing requests from this > virtqueue. 1 - enabled; 0 - disabled. > > While this is not a conformance clause this strongly implies that > queues which are not enabled are never accessed by device. > > Yuri I am guessing you are not enabling these unused queues right?
Of course, we (Windows driver) do not. The code of virtio-net passes max_queues to vhost and this causes vhost to try accessing all the queues, fail on unused ones and finally leave vhost disabled at all. > > > > > > > > > Thanks > > > > > > > > > > + > > > > + n->curr_queues = queues; > > > > + > > > > virtio_net_set_status(vdev, vdev->status); > > > > virtio_net_set_queues(n); > > > >
