Re: [virtio] [OASIS Issue Tracker] Created: (VIRTIO-28) Implement new balloon device (ID 13)

[Rusty Russell <rusty@au1.ibm.com>]

Amit Shah <amit.shah@redhat.com> writes:
> On (Wed) 11 Sep 2013 [04:51:39], OASIS Issues Tracker wrote:
>> Implement new balloon device (ID 13)
>> ------------------------------------
>> 
>>                  Key: VIRTIO-28
>>                  URL: http://tools.oasis-open.org/issues/browse/VIRTIO-28
>>              Project: OASIS Virtual I/O Device (VIRTIO) TC
>>           Issue Type: New Feature
>>             Reporter: Rusty Russell
>> 
>> 
>> The current virtio balloon device is bad enough that fixing it yields something completely incompatible:
>> 1) The page size is 4096, always, rather than some configurable page size.
>> 2) Page numbers are 32 bits.
>> 3) The deflate queue is not actually used by any device implementation (see issue virtio-25).
>> 4) The "actual" number is kind of useless, and (along with the deflate queue) requires the guest to track pages, rather than just faulting them in.
>> 5) The config is little-endian by mistake (may not matter).
>
> The current design is weird: the host tells the guest the offset by
> which to inflate or deflate the balloon.  Instead, the host should let
> the guest know how much in absolute terms the memory should be
> adjusted to, and the guest will take the decision on whether to
> inflate, or deflate, or not take any action at all.

I see your point.  I wonder how east it is define how much memory the
guest has (from a guest perspective).  Things like memory holes, device
memory maps and I'm sure there is other platform-specific weirdness I'm
sure I don't understand.

I could be wrong though?

Rusty.