Re: [PATCH v2 1/6] virtio_balloon: transitional interface

On Wed, Apr 01, 2015 at 12:22:44PM +0200, Cornelia Huck wrote:

On Wed, 1 Apr 2015 11:43:46 +0200
"Michael S. Tsirkin" [off-list ref] wrote:

quoted

On Wed, Apr 01, 2015 at 07:53:14PM +1030, Rusty Russell wrote:

quoted

"Michael S. Tsirkin" [off-list ref] writes:

quoted

On Wed, Apr 01, 2015 at 02:17:23PM +1030, Rusty Russell wrote:

quoted

I would leave the device *exactly* as is, ugly structure packing and
all.

But why?  It's going to be used for years, might as well make it clean?

Because the only spec which currently exists says to do that.

OK but the only spec which currently exists also says it's a legacy only
device, so driver must not set VERSION_1.  So surely, we can make minor
changes when VERSION_1 is set, like we did for other devices.

But we don't plan to replace the other devices, so it makes sense to do
some changes for 1.0.

I'm not sure what the above says. Do you agree with
making minor changes in device behaviour?
Also to be clear, I think this is 1.1 material.

quoted

Let me post the latest patches I'm working on,
see what you think then.

quoted

 We do
need a new virtio memballoon spec, but it'll look nothing like this
anyway.

Cheers,
Rusty.

I think it's going to have significantly different semantics, too,
so not much value in making that one work with current
drivers, right?

So why not just keep virtio-balloon as-is and just specify endianness
etc. for 1.0? Keeps the old drivers going without hacks,
and we can
start with a fresh driver for the new virtio-balloon.

Well it doesn't really, we need cpu_to_virtio in a bunch of
places anyway.

So I kind of prefer making it clean, even just to avoid setting a bad
example for other devices.

Let me post the new patch where it's all fixed in a cleaner way, and
everyone can discuss whether it's too much work.

-- 
MST