Re: [PATCH RFC] virtio_pci: fix virtio spec compliance on restore

[Michael S. Tsirkin]

On Wed, Sep 24, 2014 at 02:27:27AM +0100, Ben Hutchings wrote:
> On Tue, 2014-09-23 at 13:32 +0300, Michael S. Tsirkin wrote:
> > On restore, virtio pci does the following:
> > + set features
> > + init vqs etc - device can be used at this point!
> > + set ACKNOWLEDGE,DRIVER and DRIVER_OK status bits
> > 
> > This is in violation of the virtio spec, which
> > requires the following order:
> > - ACKNOWLEDGE
> > - DRIVER
> > - init vqs
> > - DRIVER_OK
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Cc: Amit Shah <amit.shah@xxxxxxxxxx>
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> [...]
> 
> What concrete problem does this fix, such that it should be applied to
> stable branches?
> 
> Ben.

It will break with hypervisors that assume spec compliant behaviour.
I would like this applied to stable branches so hypervisors don't
need to support broken behaviour forever.

-- 
MST
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