Re: [PATCH v2 1/3] cpu-models: add "disable-deprecated-feats" option to cpu model expansion

[Daniel P . Berrangé]

On Tue, Apr 23, 2024 at 05:06:53PM -0400, Collin Walling wrote:
> This optional parameter for query-cpu-model-expansion enables CPU
> model features flagged as deprecated to appear in the resulting
> list of properties.
> 
> This commit does not add support beyond adding a new argument
> to the query. All queries with this option present will result
> in an error claiming this option is not supported.
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> ---
>  qapi/machine-target.json         | 7 ++++++-
>  target/arm/arm-qmp-cmds.c        | 7 +++++++
>  target/i386/cpu-sysemu.c         | 7 +++++++
>  target/s390x/cpu_models_sysemu.c | 7 +++++++
>  4 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/qapi/machine-target.json b/qapi/machine-target.json
> index 29e695aa06..b9da284d2d 100644
> --- a/qapi/machine-target.json
> +++ b/qapi/machine-target.json
> @@ -285,6 +285,10 @@
>  #
>  # @type: expansion type, specifying how to expand the CPU model
>  #
> +# @disable-deprecated-feats: include CPU model features that are
> +#     flagged as deprecated. If supported, these features will appear
> +#     in the properties list paired with false.
> +#
>  # Returns: a CpuModelExpansionInfo describing the expanded CPU model
>  #
>  # Errors:
> @@ -298,7 +302,8 @@
>  ##
>  { 'command': 'query-cpu-model-expansion',
>    'data': { 'type': 'CpuModelExpansionType',
> -            'model': 'CpuModelInfo' },
> +            'model': 'CpuModelInfo',
> +            '*disable-deprecated-feats': 'bool' },
>    'returns': 'CpuModelExpansionInfo',
>    'if': { 'any': [ 'TARGET_S390X',
>                     'TARGET_I386',

I think this is an odd design approach. Lets consider the
current output:

(QEMU) query-cpu-model-expansion type=static model={"name":"z14"}
{
    "return": {
        "model": {
            "name": "z14-base",
            "props": {
                "aefsi": true,
                "aen": true,
                ...snip...
                "vxpd": true,
                "zpci": true
            }
        }
    }
}


If we want to inform a mgmt app of some features being deprecated,
why not just unconditionally include that info in the reply thus:


(QEMU) query-cpu-model-expansion type=static model={"name":"z14"}
{
    "return": {
        "model": {
            "name": "z14-base",
            "props": {
                "aefsi": true,
                "aen": true,
                ...snip...
                "vxpd": true,
                "zpci": true
            }
            "deprecated-props": ["ppa15", "ri"]
        }
    }
}



With regards,
Daniel
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