Re: [PATCH-for-6.2 v12] qapi: introduce 'query-x86-cpuid' QMP command.

[Philippe Mathieu-Daudé]

On 7/28/21 2:54 PM, Valeriy Vdovin wrote:
> Introducing new QMP command 'query-x86-cpuid'. This command can be used to
> get virtualized cpu model info generated by QEMU during VM initialization in
> the form of cpuid representation.
> 
> Diving into more details about virtual CPU generation: QEMU first parses 
> '-cpu'
> command line option. From there it takes the name of the model as the basis 
> for
> feature set of the new virtual CPU. After that it uses trailing '-cpu' 
> options,
> that state if additional cpu features should be present on the virtual CPU or
> excluded from it (tokens '+'/'-' or '=on'/'=off').
> After that QEMU checks if the host's cpu can actually support the derived
> feature set and applies host limitations to it.
> After this initialization procedure, virtual CPU has it's model and
> vendor names, and a working feature set and is ready for identification
> instructions such as CPUID.
> 
> To learn exactly how virtual CPU is presented to the guest machine via CPUID
> instruction, new QMP command can be used. By calling 'query-x86-cpuid'
> command, one can get a full listing of all CPUID leaves with subleaves which 
> are
> supported by the initialized virtual CPU.
> 
> Other than debug, the command is useful in cases when we would like to
> utilize QEMU's virtual CPU initialization routines and put the retrieved
> values into kernel CPUID overriding mechanics for more precise control
> over how various processes perceive its underlying hardware with
> container processes as a good example.
> 
> The command is specific to x86. It is currenly only implemented for KVM 
> acceleator.
> 
> Output format:
> The output is a plain list of leaf/subleaf argument combinations, that
> return 4 words in registers EAX, EBX, ECX, EDX.
> 
...

> +##
> +# @query-x86-cpuid:
> +#
> +# Returns raw data from the emulated CPUID table for the first VCPU.
> +# The emulated CPUID table defines the response to the CPUID
> +# instruction when executed by the guest operating system.
> +#
> +# Returns: a list of CpuidEntry
> +#
> +# Since: 6.1
> +##

Unfortunately too late for 6.1, so you'll have to update that to
"6.2" (also in @CpuidEntry).