> On 14 Aug 2026, at 7:08 PM, Eric Auger <[email protected]> wrote: > > !-------------------------------------------------------------------| > CAUTION: External Email > > |-------------------------------------------------------------------! > > Hi Khushit, > > On 8/5/26 8:47 AM, Khushit Shah wrote: >> >>> On 4 Aug 2026, at 12:15 PM, Markus Armbruster <[email protected]> wrote: >>> >>> !-------------------------------------------------------------------| >>> CAUTION: External Email >>> >>> |-------------------------------------------------------------------! >>> >>> 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. > > How does x86 handle this at the moment, they don't have the cmd either? > How do they currently introspect what are the valid values for a > specific host? Is it easier for them?
x86 is much simpler, all the cpu features properties are backed by cpuid bits and assumption is simple, if host value is “true”, “false" is supported, and if the host value is “false", “true" is not supported. Warm Regards, Khushit > > > Thanks > > Eric >> >> >> >
