Re: [RFC PATCH v3 16/19] qmp: add query-cpu-props-info command

> On 4 Aug 2026, at 12:15 PM, Markus Armbruster <[email protected]> wrote:
> 
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> Khushit Shah <[email protected]> writes:
> 
>> Introduce the 'query-cpu-props-info' QMP command. For CPU model
>> properties it reports the type (boolean or number) and the set of values
>> supported under the active accelerator and host.
>> 
>> For numbers the supported values are expressed as a list of inclusive
>> {min, max} ranges; for booleans as the list of allowed true/false
>> values.
>> 
>> The command and its return types (CpuPropertyType, CpuPropertyInfo and
>> friends) are defined in qapi/machine.json rather than an Arm-specific
>> schema, since the concept applies to other targets (e.g. x86, riscv)
>> too. Target that do not implement it return an error.
>> 
>> The Arm/KVM implementation spins up a scratch "host" vCPU object,
>> walks its QOM properties: SYSREG_ ID-register fields become 'number'
>> properties whose ranges come from arm_field_get_supported_values(),
>> and the advertised feature toggles become 'boolean' properties.
>> 
>> Signed-off-by: Khushit Shah <[email protected]>
> 
> This explains what the command does and how it's implemented.  It's
> silent on the most important aspect: why do we want the command?  What
> is its intended purpose?

Will add something like:

This helps the management stack to discover which values are supported
for a given CPU property. This is especially important for non-boolean
properties, where knowing that the host has value 'x' does not inherently
reveal the full range of valid values supported on the host.