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?
> +
> +##
> +# @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?
> +
> +##
> +# @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
