Re: [Qemu-devel] [PATCH 1/3] qmp: Add query-host-cpu command

[Eric Blake <eblake@redhat.com>]

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On 06/20/2016 02:12 PM, Eduardo Habkost wrote:
> The command can be used to return host-specific CPU capabilities
> information.
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  include/sysemu/arch_init.h       |  1 +
>  qapi-schema.json                 | 36 ++++++++++++++++++++++++++++++++++++
>  qmp-commands.hx                  |  6 ++++++
>  qmp.c                            | 13 +++++++++++++
>  stubs/Makefile.objs              |  1 +
>  stubs/arch-query-host-cpu-info.c |  8 ++++++++
>  6 files changed, 65 insertions(+)
>  create mode 100644 stubs/arch-query-host-cpu-info.c
> 
> diff --git a/include/sysemu/arch_init.h b/include/sysemu/arch_init.h
> index d690dfa..54215ab 100644
> --- a/include/sysemu/arch_init.h
> +++ b/include/sysemu/arch_init.h
> @@ -35,5 +35,6 @@ int kvm_available(void);
>  int xen_available(void);
>  
>  CpuDefinitionInfoList *arch_query_cpu_definitions(Error **errp);
> +void arch_query_host_cpu_info(HostCPUInfo *r, bool migratable, Error **errp);
>  
>  #endif
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 19e3ef2..d2f4879 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -3047,6 +3047,42 @@
>  ##
>  { 'command': 'query-cpu-definitions', 'returns': ['CpuDefinitionInfo'] }
>  
> +
> +##
> +# @HostCPUInfo:
> +#
> +# Information on CPU capabilities supported by the current host.
> +#
> +# @qom-properties: #optional Values of CPU QOM properties corresponding
> +#                  to CPU capabilities supported by the host.
> +#
> +# Most properties returned in qom-properties are boolean properties
> +# indicating if a feature can be enabled in the current host. Other
> +# non-boolean properties may be returned, the semantics of each property
> +# depend on the architecture-specific code that handle them.
> +#
> +# Since: 2.7.0

Most places in .json files list just 'Since: x.y' rather than 'x.y.z',
but we aren't consistent enough to insist either way on including or
excluding a micro release number.

> +##
> +{ 'struct': 'HostCPUInfo',
> +  'data': { '*qom-properties': 'any' } }

This is a big hammer that makes the properties non-introspectible - a
client can tell that properties will be returned, but cannot tell which
properties to expect nor what format to expect for a given property
name.  I don't know that the interface could be made easily
introspectible or not (it would probably require some QAPI unions, and a
LOT more generated code).  So it would be nice if we could explore how
hard it would be to use a type-safe representation instead of 'any',
before declaring that this is the best we can do.  Or, it may be the
sign of a bigger issue that we have no good way to introspect what qom
properties to expect, in general (and that solving that would also solve
this).

> +
> +##
> +# @query-host-cpu:
> +#
> +# @migratable: #optional If false, unmigratable features will be
> +#              returned as well. If true, only migratable features
> +#              will be returned. Defaults to true.
> +#
> +# Return information about CPU capabilities in the current host.
> +# The returned data may depend on machine and accelerator configuration.
> +#
> +# Returns: A HostCPUInfo object.
> +#
> +# Since: 2.7.0
> +##
> +{ 'command': 'query-host-cpu', 'data': { '*migratable': 'bool' },
> +  'returns': 'HostCPUInfo' }
> +
>  # @AddfdInfo:

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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