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Subject: Re: [Qemu-devel] [PATCH 1/5] virtio-net: Make tx_timer timeout
	configurable
From: Alex Williamson <alex.williamson@redhat.com>
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Date: Tue, 31 Aug 2010 12:07:16 -0600
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To: Chris Wright <chrisw@sous-sol.org>
Cc: jes.sorensen@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org

On Tue, 2010-08-31 at 11:00 -0700, Chris Wright wrote:
> * Alex Williamson (alex.williamson@redhat.com) wrote:
> > diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> > index 075f72d..9ef29f0 100644
> > --- a/hw/virtio-net.c
> > +++ b/hw/virtio-net.c
> > @@ -36,6 +36,7 @@ typedef struct VirtIONet
> >      VirtQueue *ctrl_vq;
> >      NICState *nic;
> >      QEMUTimer *tx_timer;
> > +    uint32_t tx_timeout;
> >      int tx_timer_active;
> >      uint32_t has_vnet_hdr;
> >      uint8_t has_ufo;
> > @@ -702,7 +703,7 @@ static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
> >          virtio_net_flush_tx(n, vq);
> >      } else {
> >          qemu_mod_timer(n->tx_timer,
> > -                       qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
> > +                       qemu_get_clock(vm_clock) + n->tx_timeout);
> >          n->tx_timer_active = 1;
> >          virtio_queue_set_notification(vq, 0);
> >      }
> > @@ -842,7 +843,7 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
> >  
> >      if (n->tx_timer_active) {
> >          qemu_mod_timer(n->tx_timer,
> > -                       qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
> > +                       qemu_get_clock(vm_clock) + n->tx_timeout);
> 
> I think I'm missing where this is stored?  Looks like migration
> would revert a changed tx_timeout back to 150us.

It's not stored, it can be instantiated on the migration target any way
you please and we can migrate between different values or even different
TX mitigation strategies.  If a non-default value is used on the source
and you want to maintain the same behavior, the target needs to be
started the same way.

Alex