Re: [PATCH 0/6] virtio_balloon: virtio 1 support

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Mar 31, 2015 at 10:46:18AM +0200, Cornelia Huck wrote:
> On Mon, 30 Mar 2015 19:37:08 +0200
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > Virtio 1.0 doesn't include a modern balloon device.
> > At some point we'll likely define an incompatible interface with a different
> > ID.  But for now, it's not a big change to support a transitional balloon
> > device: this has the advantage of supporting existing drivers, transparently.
> 
> This is needed to support a ballooner on transports that don't support
> mixing legacy and 1.0, right?

That too. But it's also useful if you don't know whether your guest
supports virtio 1 or not - which is the point of using
a transitional device.

> > 
> > The only issue is with the stats buffer, which has misaligned fields.
> > Seems easy to fix by prepending a 6 byte reserved field.
> 
> I assume you also define the stats fields to be le for 1.0?

They were always le for the balloon.

> > 
> > I'll post spec patch and qemu patches shortly.
> 
> I'll defer review until then.
> 
> > 
> > Michael S. Tsirkin (6):
> >   virtio_balloon: transitional interface
> >   virtio: balloon might not be a legacy device
> >   virtio_ccw: support non-legacy balloon devices
> >   virtio_mmio: support non-legacy balloon devices
> >   virtio_pci: support non-legacy balloon devices
> >   virtio: drop virtio_device_is_legacy_only
> > 
> >  include/linux/virtio.h              |  2 --
> >  include/uapi/linux/virtio_balloon.h |  6 ++++++
> >  drivers/s390/kvm/virtio_ccw.c       | 10 +++-------
> >  drivers/virtio/virtio.c             |  6 ------
> >  drivers/virtio/virtio_balloon.c     |  8 ++++++--
> >  drivers/virtio/virtio_mmio.c        |  8 --------
> >  drivers/virtio/virtio_pci_modern.c  |  3 ---
> >  7 files changed, 15 insertions(+), 28 deletions(-)
> >