On Tue, Oct 08, 2013 at 11:39:10AM +0100, Pawel Moll wrote:
> On Fri, 2013-10-04 at 04:36 +0100, Rusty Russell wrote:
> > +• 0x018 | R | ConfigGeneration
> > + Configuration atomicity value.
> > + Changes every time the configuration noticeably changes. This means the
> > + device may only change the value after a configuration read operation,
> > + but it must change if there is any risk of a device seeing an inconsistent
> > + configuration state.
>
> How about moving it closer to the config space? Something like 0x0f0 or
> even 0x0fc?
>
> > +2.3.2.2.1. Legacy Interface: MMIO Device Layout
> > +--------------------------
> > +The ConfigGeneration field does not exist in legacy devices; fortunately
> > +it would return 0 if accessed.
>
> Not on "my" models, no. It would result in external abort (think
> SIGBUS).
>
> Not a big problem - the device version number will be bumped to 2 anyway
> (working on it right now).
>
> Paweł
>
Hmm do current guests check version number?
Transitional devices should support both old and
new guests.
For transitional I think the right thing to do is
to key off the VIRTIO_1 feature bit and/or FEATURES_OK.
--
MST
