Re: [libvirt] [Qemu-devel] [PATCH 5/7] qapi: add query-cpudefs command

[Luiz Capitulino]

On Fri, 27 Jul 2012 08:37:17 -0500
Anthony Liguori  wrote:

> This command attempts to map to the behavior of -cpu ?.  Unfortunately, the
> output of this command differs wildly across targets.
> 
> To accomodate this, we use a weak symbol to implement a default version of the
> command that fails with a QERR_NOT_SUPPORTED error code.  Targets can then
> override and implement this command if it makes sense for them.
> 
> Signed-off-by: Anthony Liguori 
> ---
>  qapi-schema.json |   23 +++
>  qmp-commands.hx  |6 ++
>  qmp.c|6 ++
>  3 files changed, 35 insertions(+), 0 deletions(-)
> 
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 5b47026..768fb44 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -2228,3 +2228,26 @@
>  # Since: 1.2.0
>  ##
>  { 'command': 'query-machines', 'returns': ['MachineInfo'] }
> +
> +##
> +# @CpuDefInfo:
> +#
> +# Virtual CPU definition.
> +#
> +# @name: the name of the CPU definition
> +#
> +# Since: 1.2.0
> +##
> +{ 'type': 'CpuDefInfo',
> +  'data': { 'name': 'str' } }
> +
> +##
> +# @query-cpudefs:

I'd call this query-cpu-defs or even query-cpu-difinitions. The latter makes
it self-documenting.

> +#
> +# Return a list of supported virtual CPU definitions
> +#
> +# Returns: a list of CpuDefInfo
> +#
> +# Since: 1.2.0
> +##
> +{ 'command': 'query-cpudefs', 'returns': ['CpuDefInfo'] }
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index a6f82fc..73dfeab 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -2228,3 +2228,9 @@ EQMP
>  .mhandler.cmd_new = qmp_marshal_input_query_machines,
>  },
>  
> +{
> +.name   = "query-cpudefs",
> +.args_type  = "",
> +.mhandler.cmd_new = qmp_marshal_input_query_cpudefs,
> +},
> +
> diff --git a/qmp.c b/qmp.c
> index 254a32f..51b4f75 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -467,3 +467,9 @@ DevicePropertyInfoList *qmp_device_list_properties(const 
> char *typename,
>  
>  return prop_list;
>  }
> +
> +CpuDefInfoList GCC_WEAK *qmp_query_cpudefs(Error **errp)
> +{
> +error_set(errp, QERR_NOT_SUPPORTED);
> +return NULL;
> +}

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Re: [libvirt] [Qemu-devel] [PATCH 5/7] qapi: add query-cpudefs command

[Anthony Liguori]

Peter Maydell  writes:

> On 27 July 2012 14:37, Anthony Liguori  wrote:
>> This command attempts to map to the behavior of -cpu ?.  Unfortunately, the
>> output of this command differs wildly across targets.
>
> I've never really understood why so much of the cpu selection
> logic is deferred to target-*...

It will be fixed as part of the QOM conversion.

>> To accomodate this, we use a weak symbol to implement a default version of 
>> the
>> command that fails with a QERR_NOT_SUPPORTED error code.  Targets can then
>> override and implement this command if it makes sense for them.
>
> This is a bit of a weak reason (boom boom!) for requiring a platform
> specific thing like weak symbols, though, and it's not how we handle
> similar existing cases (eg see the configure/makefile logic for
> memory_mapping.c vs memory_mapping-stub.c).

I don't think we have a consistent approach today FWIW.  I think using
weak symbols is sufficiently compelling that it will become consistent.

>
> If having separate configure/make stuff for each of these things
> sounds a bit heavyweight, we could just have a target-stubs.c which
> #includes cpu.h and has a lot of
> #ifndef TARGET_QUERY_CPUDEFS
> [stub version]
> #endif
> #ifndef TARGET_GET_MEMORY_MAPPING
> [stub version]
> #endif

This is pretty hideous.

FWIW, weak symbols are supported on OS X as of 10.2.

Regards,

Anthony Liguori

>
> etc.
>
> -- PMM

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