Re: [PATCH 07/16] virtio-net: support queue reset

[Kangjie Xu]

在 2022/7/27 14:59, Jason Wang 写道:
> On Wed, Jul 27, 2022 at 2:25 PM Kangjie Xu <kangjie.xu@linux.alibaba.com> wrote:
> > 在 2022/7/27 13:00, Jason Wang 写道:
> > > On Tue, Jul 26, 2022 at 3:02 PM Kangjie Xu <kangjie.xu@linux.alibaba.com> wrote:
> > > > 在 2022/7/26 11:43, Jason Wang 写道:
> > > > > 在 2022/7/18 19:17, Kangjie Xu 写道:
> > > > > > From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > > >
> > > > > > virtio-net implements queue reset. Queued packets in the corresponding
> > > > > > queue pair are flushed or purged.
> > > > > >
> > > > > > Queue reset is currently only implemented for non-vhosts.
> > > > > >
> > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > > > > > ---
> > > > > >     hw/net/virtio-net.c | 15 +++++++++++++++
> > > > > >     1 file changed, 15 insertions(+)
> > > > > >
> > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> > > > > > index 7ad948ee7c..8396e21a67 100644
> > > > > > --- a/hw/net/virtio-net.c
> > > > > > +++ b/hw/net/virtio-net.c
> > > > > > @@ -531,6 +531,19 @@ static RxFilterInfo
> > > > > > *virtio_net_query_rxfilter(NetClientState *nc)
> > > > > >         return info;
> > > > > >     }
> > > > > >     +static void virtio_net_queue_reset(VirtIODevice *vdev, uint32_t
> > > > > > queue_index)
> > > > > > +{
> > > > > > +    VirtIONet *n = VIRTIO_NET(vdev);
> > > > > > +    NetClientState *nc = qemu_get_subqueue(n->nic, vq2q(queue_index));
> > > > > > +
> > > > > > +    if (!nc->peer) {
> > > > > > +        return;
> > > > > > +    }
> > > > > > +
> > > > > > +    qemu_flush_or_purge_queued_packets(nc->peer, true);
> > > > > > +    assert(!virtio_net_get_subqueue(nc)->async_tx.elem);
> > > > > Let's try to reuse this function in virtio_net_reset().
> > > > Yeah, I'll fix it.
> > > >
> > > > Thanks.
> > > >
> > > > > > +}
> > > > > > +
> > > > > >     static void virtio_net_reset(VirtIODevice *vdev)
> > > > > >     {
> > > > > >         VirtIONet *n = VIRTIO_NET(vdev);
> > > > > > @@ -741,6 +754,7 @@ static uint64_t
> > > > > > virtio_net_get_features(VirtIODevice *vdev, uint64_t features,
> > > > > >         }
> > > > > >           if (!get_vhost_net(nc->peer)) {
> > > > > > +        virtio_add_feature(&features, VIRTIO_F_RING_RESET);
> > > > > This breaks migration compatibility.
> > > > >
> > > > > We probably need:
> > > > >
> > > > > 1) a new command line parameter
> > > > > 2) make it disabled for pre-7.2 machine
> > > > >
> > > > > Thanks
> > > > Sorry, I don't get what is the meaning of "pre-7.2 machine". Could you
> > > > please explain it?
> > > I meant for pre 7.2 machine type, we should make reset fault off by default.
> > >
> > > Otherwise we break migration compatibility.
> > >
> > > Thanks
> > Sorry, I did not express myself clearly. Is "7.2" the version of a
> > system or a module? If it is a system version, what is the system?
> It's the machine type to make sure the migration can work. (you can
> get the list of those types via qemu -machine ?)
>
> E.g you can start a 7.0 machine on Qemu 7.1 and it guarantees to be
> migrated to 7.0 machine on Qemu 7.0.
>
> > I did not have backgrond knowledge related to this part and will
> > investigate migration issues afterwards.
> Git grep hw_compat_7_0 may give you more hints.
>
> Thanks

Okay, I get it.

Thanks for your guidelines.


> > Thanks.
> >
> > > > Thanks
> > > >
> > > > > >             return features;
> > > > > >         }
> > > > > >     @@ -3766,6 +3780,7 @@ static void virtio_net_class_init(ObjectClass
> > > > > > *klass, void *data)
> > > > > >         vdc->set_features = virtio_net_set_features;
> > > > > >         vdc->bad_features = virtio_net_bad_features;
> > > > > >         vdc->reset = virtio_net_reset;
> > > > > > +    vdc->queue_reset = virtio_net_queue_reset;
> > > > > >         vdc->set_status = virtio_net_set_status;
> > > > > >         vdc->guest_notifier_mask = virtio_net_guest_notifier_mask;
> > > > > >         vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;