[libvirt] [Qemu-devel] [PATCH v3 4/6] numa: introduce "numa-mem-supported" machine property

[Markus Armbruster]

Igor Mammedov <imammedo at redhat.com> writes:

> '-numa mem' option has a number of issues and mgmt often defaults
> to it. Unfortunately it's no possible to replace it with an alternative
> '-numa memdev' without breaking migration compatibility.

To be precise: -numa node,mem=... and -numa node,memdev=...  Correct?

>                                                          What's possible
> though is to deprecate it, keeping option working with old machine types.
> Once deprecation period expires, QEMU will disable '-numa mem' option,
> usage on new machine types and when the last machine type that supported
> it is removed we would be able to remove '-numa mem' with associated code.
>
> In order to help mgmt to find out if being deprecated CLI option
> '-numa mem=SZ' is still supported by particular machine type, expose
> this information via "numa-mem-supported" machine property.
>
> Users can use "qom-list-properties" QMP command to list machine type
> properties including initial proprety values (when probing for supported
> machine types with '-machine none') or at runtime at preconfig time
> before numa mapping is configured and decide if they should used legacy
> '-numa mem' or alternative '-numa memdev' option.

This sentence is impenetrable, I'm afraid :)

If we only want to convey whether a machine type supports -numa
node,mem=..., then adding a flag to query-machines suffices.  Since I'm
pretty sure you'd have figured that out yourself, I suspect I'm missing
something.  Can you give me some examples of intended usage?