Re: [PATCH 1/2] qmp: Support fd-based KVM stats query

[Paolo Bonzini]

On 19/10/21 22:29, Mark Kanda wrote:
> +#
> +# @filter: KVM stat name (optional)

Nitpicking on the name, "filter" makes me think that some kind of 
globbing is supported.  So I would just call it "name".

Also nitpicking on the name, let's drop "kvm" from everything.  In the 
future other subsystems could expose statistics, both in the kernel and 
in QEMU (e.g. vhost or TAP; even query-blockstats could be integrated).

Finally, I think we should decouple the description of the stats and the 
description of the sources of said stats.  For example:

   name                 type
   ----                 ----
   vm                   kvm-vm
   vcpu_0               kvm-vcpu
   ...

This way the caller knows that the "vcpu_*" stats follow the same 
schema. That would be:

# e.g. name: 'vm', 'type: 'kvm-vm'
# or name: 'vcpu_0', 'type: 'kvm-vcpu'
{ 'struct': 'StatsInstance',
  'data': {'name': 'str', 'type': 'str'}}

{ 'struct': 'StatsSchema',
  'data': {'type': 'str', 'stats': [ 'KvmStatSchema' ] } }

{ 'struct': 'StatsValues',
  'data': {'name': 'str', type': 'str', 'values': [ 'int64' ] } }

{ 'command': 'query-stats-instances',
  'returns': [ 'StatsInstances' ] }

{ 'command': 'query-stats-schemas',
  'data': { '*type': 'str' },
  'returns': [ 'StatsSchema' ] }

{ 'command': 'query-stats',
  'data': { '*name': 'str', '*type': 'str' },
  'returns': [ 'StatsValues' ] }

This should be enough to make the API more future proof.

Paolo