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).