On 02/24/2016 07:31 AM, Michael S. Tsirkin wrote:
>> One of the benefits is forward compatibility, so that counters that have
>> graduated into supported ones and have got their own number and name,
>> can be made to work with qemu that doesn't yet recognize them.
> 
> Then management does start relying on the x- prefixed things,
> and once it's used to that it's a slippery slope.

Any management tool that relies on an x- prefix name is broken.  We've
explicitly documented that the x- prefix is unstable and liable to go
away with a future release. Any management app that wants to use a
feature beginning with x- should FIRST push hard to get the x- removed
and stabilize the interface (and libvirt, at least, does just that).

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org