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Resolve VIRTIO-143: balloon: allow transitional devices

Should the TC accept changes listed in the description to resolve issue VIRTIO-143, for inclusion in specification version(s) "virtio 1.0 cs03", and future versions of the specification?

Please vote Yes if you agree with all of the following.
If you disagree, please vote No.
If you don't have an opinion, please vote Abstain.

I move that:
The TC agrees to resolve the following specification issue:
VIRTIO-143: balloon: allow transitional devices
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Virtio 1.0 cs02 doesn't include a modern balloon device. At some
point we'll likely define an incompatible interface with a
different ID and different semantics. But for now, it's not a
big effort to support a transitional balloon device: this has the
advantage of supporting existing drivers, transparently, as well
as transports that don't allow mixing virtio 0 and virtio 1
devices. And balloon is an easy device to test, so it's also
useful for people to test virtio core handling of transitional
devices.

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The TC accepts the following proposed changes to the specification:
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mid.gmane.org/1430235439-3812-1-git-send-email-mst@redhat.com

[PATCH v3] balloon: transitional device support

Support a transitional balloon device: this has the advantage of supporting
existing drivers, transparently, as well as transports that don't allow mixing
virtio 0 and virtio 1 devices. And balloon is an easy device to test, so it's
also useful for people to test virtio core handling of transitional devices.

Three issues with legacy hypervisors have been identified:
1. Actual value is actually used, and is necessary for management
to work. Luckily 4 byte config space writes are now atomic.
When using old guests, hypervisors can detect access to the last byte.
When using old hypervisors, drivers can use atomic 4-byte accesses.
2. Hypervisors actually didn't ignore the stats from the first
buffer supplied. This means the values there would be
incorrect until hypervisor resends the request.
Add a note suggesting hypervisors ignore the 1st buffer.
3. QEMU simply over-writes stats from each buffer it gets.
Thus if driver supplies a different subset of stats
on each request, stale values will be there.
Require drivers to supply the same subset on each
request. This also gives us a simple way to figure out
which stats are supported.

Additionally, this fixes a typo:
- the driver SHOULD omit unsupported statistics.
should be:
+ devices omit unsupported statistics.

Note that we have a normative statement with this requirement
already, this is just general high-level description.

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The TC agrees to include the above change(s) in specification version(s) "virtio 1.0 cs03", and future versions of the
specification.

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Reminder: A Voting Member must be active in a TC to maintain voting rights. As
the Virtio TC has adopted a standing rule to conduct business only by
electronic ballot, without Meetings, a Voting Member who fails to cast a ballot
in two consecutive Work Product Ballots loses his or her voting rights at the
close of the second ballot missed.

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 [ ]  Yes
 [ ]  No
 [ ]  Abstain
Opening:   Monday, 11 May 2015 @ 12:45 am EDT
Closing:   Monday, 18 May 2015 @ 12:45 am EDT
Group:   OASIS Virtual I/O Device (VIRTIO) TC
Ballot has closed.

Referenced Items
Name Type Date Action
Document
2015-05-17

Voting Details

Voting Summary

Options with highest number of votes are bold

Option # Votes % of Total
Yes 6 100%
No 0 0%
Abstain 0
Eligible members who have voted: 6 of 8 75%
Eligible members who have abstained: 0 of 8 0%
Eligible members who have not voted: 2 of 8 25%

Voting Details

Voter Company VoteReference Document and/or Comment
Pawel Moll
ARM Limited
Yes
 
Rusty Russell
IBM
--
 
Cornelia Huck
IBM
Yes
Bryan Venteicher
NetApp
Yes
 
Daniel Kiper
Oracle
Yes
 
James Bottomley
Parallels IP Holdings GmbH
Yes
 
Amit Shah
Red Hat
--
 
Michael Tsirkin
Red Hat
Yes