Re: [PATCH] virtio-net: Fix save/load

[Alex Williamson <alex.williamson@hp.com>]

Hi Mark,

On Thu, 2009-01-15 at 18:21 +0000, Mark McLoughlin wrote:
> Actually, we really need to handle VLANClientState:link_down for all
> vlan clients, not just virtio-net and then update status on load
> according to link_down.
> 
> It's not critically important, though - if we neglect to save/load this
> the only side effect is that "set link down" would have to be called
> again. Does need to be fixed, though.

The link status may be able to get away w/o a save/load, but what else
is going to get added to there later.  Seems like we might as well add
it now.

> > +/*
> > + * Anything added here should cause a bump in VIRTIO_NET_VM_VERSION
> > + * and appropriate conditionalized load with sane defaults for older
> > + * images should be added to virtio_net_load().
> > + */
> 
> This is true for all savevm() code, so I don't think we need the comment
> here.

Doesn't hurt and it's obviously easy to forget ;)

> >  static int virtio_net_load(QEMUFile *f, void *opaque, int
> version_id)
> >  {
> >      VirtIONet *n = opaque;
> >  
> > -    if (version_id != 2)
> > +    if (version_id < 3 || version_id > VIRTIO_NET_VM_VERSION)
> 
> This bit isn't right - how can this code load e.g. version 4?

It can't.  There's no way to load a save image for a version_id greater
than VIRTIO_NET_VM_VERSION, because we don't know how much data to pop
off or what state we'd be missing.  We can only load older save images
on equal or newer versions of qemu.  As far as know...  Thanks,

Alex

-- 
Alex Williamson                             HP Open Source & Linux Org.