Re: [PATCH] virtio_net: enable tx after resuming from suspend

[Jason Wang]

On 2018/10/15 äå6:08, ake wrote:
> On 2018å10æ12æ 18:18, ake wrote:
> > On 2018å10æ12æ 17:23, Jason Wang wrote:
> > > On 2018å10æ12æ 12:30, ake wrote:
> > > > On 2018å10æ11æ 22:06, Jason Wang wrote:
> > > > > On 2018å10æ11æ 18:22, ake wrote:
> > > > > > On 2018å10æ11æ 18:44, Jason Wang wrote:
> > > > > > > On 2018å10æ11æ 15:51, Ake Koomsin wrote:
> > > > > > > > commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
> > > > > > > > disabled the virtio tx before going to suspend to avoid a use after
> > > > > > > > free.
> > > > > > > > However, after resuming, it causes the virtio_net device to lose its
> > > > > > > > network connectivity.
> > > > > > > >
> > > > > > > > To solve the issue, we need to enable tx after resuming.
> > > > > > > >
> > > > > > > > Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during
> > > > > > > > reset")
> > > > > > > > Signed-off-by: Ake Koomsin <ake@xxxxxxxxxx>
> > > > > > > > ---
> > > > > > > >  ÂÂÂ drivers/net/virtio_net.c | 1 +
> > > > > > > >  ÂÂÂ 1 file changed, 1 insertion(+)
> > > > > > > >
> > > > > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > > > > > index dab504ec5e50..3453d80f5f81 100644
> > > > > > > > --- a/drivers/net/virtio_net.c
> > > > > > > > +++ b/drivers/net/virtio_net.c
> > > > > > > > @@ -2256,6 +2256,7 @@ static int virtnet_restore_up(struct
> > > > > > > > virtio_device *vdev)
> > > > > > > >  ÂÂÂÂÂÂÂ }
> > > > > > > >  ÂÂÂ ÂÂÂÂÂ netif_device_attach(vi->dev);
> > > > > > > > +ÂÂÂ netif_start_queue(vi->dev);
> > > > > > > I believe this is duplicated with netif_tx_wake_all_queues() in
> > > > > > > netif_device_attach() above?
> > > > > > Thank you for your review.
> > > > > >
> > > > > > If both netif_tx_wake_all_queues() and netif_start_queue() result in
> > > > > > clearing __QUEUE_STATE_DRV_XOFF, then is it possible that some
> > > > > > conditions in netif_device_attach() is not satisfied?
> > > > > Yes, maybe. One case I can see now is when the device is down, in this
> > > > > case netif_device_attach() won't try to wakeup the queue.
> > > > >
> > > > > >  ÂÂ Without
> > > > > > netif_start_queue(), the virtio_net device does not resume properly
> > > > > > after waking up.
> > > > > How do you trigger the issue? Just do suspend/resume?
> > > > Yes, simply suspend and resume.
> > > >
> > > > Here is how I trigger the issue:
> > > >
> > > > 1) Start the Virtual Machine Manager GUI program.
> > > > 2) Create a guest Linux OS. Make sure that the guest OS kernel is
> > > >  ÂÂÂ >= 4.12. Make sure that it uses virtio_net as its network device.
> > > >  ÂÂÂ In addition, make sure that the video adapter is VGA. Otherwise,
> > > >  ÂÂÂ waking up with the virtual power button does not work.
> > > > 3) After installing the guest OS, log in, and test the network
> > > >  ÂÂÂ connectivity by ping the host machine.
> > > > 4) Suspend. After this, the screen is blank.
> > > > 5) Resume by hitting the virtual power button. The login screen
> > > >  ÂÂÂ appears again.
> > > > 6) Log in again. The guest loses its network connection.
> > > >
> > > > In my test:
> > > > Guest: Ubuntu 16.04/18.04 with kernel 4.15.0-36-generic
> > > > Host: Ubuntu 16.04 with kernel 4.15.0-36-generic/4.4.0-137-generic
> > > I can not reproduce this issue if virtio-net interface is up in guest
> > > before the suspend. I'm using net-next.git and qemu master. But I do
> > > reproduce when virtio-net interface is down in guest before suspend,
> > > after resume, even if I make it up, the network is still lost.
> > >
> > > I think the interface is up in your case, but please confirm this.
> > If you mean the interface state before I hit the suspend button,
> > the answer is yes. The interface is up before I suspend the guest
> > machine.
> >
> > Note that my current QEMU version is QEMU emulator version 2.5.0
> > (Debian 1:2.5+dfsg-5ubuntu10.32).
> >
> > I will try with net-next.git and qemu master later and see if I can
> > reproduce the issue.
> Update. I tried with net-next and qemu master. Interestingly, the result
> is different from yours. The network is lost even if the virtio_net
> interface is up before suspending.
>
> Host: Ubuntu 16.04 with net-next kernel (default configuration)
> Guest: Ubuntu 18.04 with net-next kernel (default configuration)
> Qemu: master
> Qemu command:
> qemu-system-x86_64 -cpu host -m 2048 -enable-kvm \
> -bios /usr/share/OVMF/OVMF_CODE.fd \
> -drive file=/var/lib/libvirt/images/virtio_test.qcow2,if=virtio \
> -netdev user,id=hostnet0 \
> -device virtio-net-pci,netdev=hostnet0 \
> -device VGA,id=video0,vgamem_mb=16 \
> -global PIIX4_PM.disable_s3=1 \
> -global PIIX4_PM.disable_s4=1 -monitor stdio


Interesting, just notice you're using userspace network. To isolate the 
issue, can you retry with e.g tap or e1000 to make sure it's not a fault 
of slirp or virito-net?

Thanks