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" [off-list ref] wrote:
quoted
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.
quoted
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
include/uapi/linux/virtio_balloon.h | 5 +++--
drivers/virtio/virtio_balloon.c | 4 ++--
2 files changed, 5 insertions(+), 4 deletions(-)
quoted
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?