On 10/16/26 8:57 AM, Khushit Shah wrote:
>
>> On 15 Oct 2026, at 7:50 PM, Eric Auger <[email protected]> wrote:
>>
>> !-------------------------------------------------------------------|
>> CAUTION: External Email
>>
>> |-------------------------------------------------------------------!
>>
>>
>>
>> On 9/21/26 2:32 PM, Khushit Shah wrote:
>>> Introduce the 'query-cpu-props-info' QMP command. For each CPU model
>>> property, it reports the type (boolean or number) and the set of values
>>> supported under the active accelerator and host.
>>>
>>> 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.
>>> For example, an Arm host with CTR_EL0.L1Ip=3 (PIPT) also allows 2
>>> (VIPT) but a host with CTR_EL0.L1Ip=2 does not allow CTR_EL0.L1Ip=3
>>> for a guest.
>>>
>>> For numerical properties, the supported values are expressed as a list
>>> of inclusive {min, max} ranges. For boolean properties, they are
>>> represented as a list of 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, RISC-V)
>>> too. Targets that do not implement it return an error.
>>> (The following commit implements the command for Arm KVM.)
>>>
>>> Signed-off-by: Khushit Shah <[email protected]>
>>> ---
>>> qapi/machine.json | 82 ++++++++++++++++++++++++++++++++++++++
>>> stubs/meson.build | 1 +
>>> stubs/qmp-cpu-props-info.c | 12 ++++++
>>> tests/qtest/qmp-cmd-test.c | 1 +
>>> 4 files changed, 96 insertions(+)
>>> create mode 100644 stubs/qmp-cpu-props-info.c
>>>
>>> diff --git a/qapi/machine.json b/qapi/machine.json
>>> index 2d63c1bac3..6e65bdad86 100644
>>> --- a/qapi/machine.json
>>> +++ b/qapi/machine.json
>>> @@ -2291,3 +2291,85 @@
>>> # Since: 1.2
>>> ##
>>> { 'command': 'query-cpu-definitions', 'returns': ['CpuDefinitionInfo'] }
>>> +
>>> +##
>>> +# @CpuPropertyType:
>>> +#
>>> +# The type of a CPU model property.
>>> +#
>>> +# @boolean: the property is of type boolean.
>>> +#
>>> +# @number: the property is of type unsigned integer.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'enum': 'CpuPropertyType',
>>> + 'data': [ 'boolean', 'number' ] }
>> why do we still need the boolean type? Can't we simplify and stick to
>> uint64_t for all SYSREG props?
> Hi Eric,
>
> Bools to support existing properties (sve, pauth, etc…) are booleans.
>>> +
>>> +##
>>> +# @CpuPropertyValueRange:
>>> +#
>>> +# An inclusive range of numeric values supported for the property.
>>> +#
>>> +# @min: the lowest supported value.
>>> +#
>>> +# @max: the highest supported value.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'struct': 'CpuPropertyValueRange',
>>> + 'data': { 'min': 'uint64', 'max': 'uint64' } }
>>> +
>>> +##
>>> +# @CpuPropertyInfoBoolean:
>>> +#
>>> +# @supported-values: list of boolean values supported for the
>>> +# property.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'struct': 'CpuPropertyInfoBoolean',
>>> + 'data': { 'supported-values': ['bool'] } }
>> why can't you model that with a range too?
> I’m sorry I didn’t get you.
I meant I don't really understand why we need to bother about boolean
props and why we don't just model everything with list of uint64 ranges.
I was puzzled by "list of boolean values supported for the property" Eric
>
> Thanks,
> Khushit
>>> +
>>> +##
>>> +# @CpuPropertyInfoNumber:
>>> +#
>>> +# @supported-values: list of numeric value ranges supported
>>> +# for the property.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'struct': 'CpuPropertyInfoNumber',
>>> + 'data': { 'supported-values': ['CpuPropertyValueRange'] } }
>>> +
>>> +##
>>> +# @CpuPropertyInfo:
>>> +#
>>> +# Information about a single CPU model property, including the values
>>> +# the host/accelerator supports for it.
>>> +#
>>> +# @name: the name of the property.
>>> +#
>>> +# @type: the type of the property, which selects the layout of
>>> +# @supported-values.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'union': 'CpuPropertyInfo',
>>> + 'base': { 'name': 'str',
>>> + 'type': 'CpuPropertyType' },
>>> + 'discriminator': 'type',
>>> + 'data': { 'boolean': 'CpuPropertyInfoBoolean',
>>> + 'number': 'CpuPropertyInfoNumber' } }
>>> +
>>> +##
>>> +# @query-cpu-props-info:
>>> +#
>>> +# Return information about the CPU model properties. For each
>>> +# property it reports the values supported under the active
>>> +# accelerator and host.
>>> +#
>>> +# Since: 11.2
>>> +##
>>> +{ 'command': 'query-cpu-props-info',
>>> + 'returns': ['CpuPropertyInfo'] }
>>> diff --git a/stubs/meson.build b/stubs/meson.build
>>> index 3b2f2680b1..3bb4028bab 100644
>>> --- a/stubs/meson.build
>>> +++ b/stubs/meson.build
>>> @@ -83,6 +83,7 @@ if have_system
>>> stub_ss.add(files('qmp-i386-sgx.c'))
>>> stub_ss.add(files('qmp-i386-xen.c'))
>>> stub_ss.add(files('qmp-cpu.c'))
>>> + stub_ss.add(files('qmp-cpu-props-info.c'))
>>> stub_ss.add(files('qmp-cpu-s390x.c'))
>>> stub_ss.add(files('qmp-cpu-s390x-kvm.c'))
>>> stub_ss.add(files('hmp-cmd-info_mem.c'))
>>> diff --git a/stubs/qmp-cpu-props-info.c b/stubs/qmp-cpu-props-info.c
>>> new file mode 100644
>>> index 0000000000..36b0530b98
>>> --- /dev/null
>>> +++ b/stubs/qmp-cpu-props-info.c
>>> @@ -0,0 +1,12 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>>> +
>>> +#include "qemu/osdep.h"
>>> +#include "qapi/error.h"
>>> +#include "qapi/qapi-commands-machine.h"
>>> +
>>> +CpuPropertyInfoList *
>>> +qmp_query_cpu_props_info(Error **errp)
>>> +{
>>> + error_setg(errp, "query-cpu-props-info not supported on this target");
>>> + return NULL;
>>> +}
>>> diff --git a/tests/qtest/qmp-cmd-test.c b/tests/qtest/qmp-cmd-test.c
>>> index 279a8f5614..2c25dbd8cb 100644
>>> --- a/tests/qtest/qmp-cmd-test.c
>>> +++ b/tests/qtest/qmp-cmd-test.c
>>> @@ -100,6 +100,7 @@ static bool query_is_ignored(const char *cmd)
>>> "add-fd",
>>> /* Success depends on target arch: */
>>> "query-cpu-definitions", /* arm, i386, ppc, s390x */
>>> + "query-cpu-props-info", /* arm + kvm */
>>> "query-gic-capabilities", /* arm */
>>> "query-s390x-cpu-polarization", /* s390x */
>>> /* Success depends on target-specific build configuration: */
>> Thanks
>>
>> Eric
>
