On Tue, Dec 02, 2014 at 07:39:30PM +0100, Cornelia Huck wrote:
> On Tue, 2 Dec 2014 13:44:06 +0200
> "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
>
> > balloon device is not part of virtio 1.0 spec. Still, it's easy enough
> > to make it handle endian-ness exactly as other virtio 1.0 devices: what
> > we gain from this, is that there's no need to special-case it in virtio
> > core.
>
> Well, the balloon is weird in a number of ways, including its always
> little-endian config space.
Hmm yes, I forgot about that.
> But I'm not quite sure the spec covers this?
The spec does not cover balloon. It merely includes a reference section
about legacy balloon device. What to do when that device sets VERSION_1
is really up to us.
Patchset v8 simply makes balloon tell core it's legacy_only.
This is I guess fine as far as it goes.
I was still looking for the best way that involves minimal noise
in core. This looked like the best way: change 4 lines,
and drop all special casing in core, but given the config space
endian-ness mess, I'm not sure anymore.
I guess we'll just stick to what v8 does for now.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > include/uapi/linux/virtio_balloon.h | 5 +++--
> > drivers/virtio/virtio_balloon.c | 4 ++--
> > 2 files changed, 5 insertions(+), 4 deletions(-)
> >
>
> > struct virtio_balloon_stat {
> > - __u16 tag;
> > - __u64 val;
> > + __virtio16 tag;
> > + __virtio64 val;
> > } __attribute__((packed));
>
> Would the respective fields in the spec need updating? While it is
> actually talking about legacy requirements, the fields are not
> specified as __virtio{16,64}.
>
> Also, is changing the stat fields enough? I've not looked into balloon
> operation, but does the payload need some endianess conversion as well?
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
