Re: [Qemu-devel] [Patch v1 25/29] qmp: add QMP interface "query-cpu-model-comparison"

[David Hildenbrand <dahi@linux.vnet.ibm.com>]

> +##
> +# @CpuModelCompareResult:
> +#
> +# An enumeration of CPU model comparation results.
> +#
> +# @incompatible: both model definition are incompatible
> +#
> +# @identical: model A == model B
> +#
> +# @superset: model A > model B
> +#
> +# @subset: model A < model B
> +#
> +# Since: 2.8.0
> +##

This comment is now:

##                                                                              
# @CpuModelCompareResult:                                                       
#                                                                               
# An enumeration of CPU model comparation results. The result is usually        
# calcualted using e.g. at CPU features or CPU generations.                     
#                                                                               
# @incompatible: If model A is incompatible to model B, model A is not          
#                guaranteed to run where model B runs and the other way around. 
#                                                                               
# @identical: If model A is identical to model B, model A is guaranteed to run  
#             where model B runs and the other way around.                      
#                                                                               
# @superset: If model A is a superset of model B, model B is guaranteed to run  
#            where model A runs. There are no guarantees about the other way.   
#                                                                               
# @subset: If model A is a subset of model B, model A is guaranteed to run      
#          where model B runs. There are no guarantees about the other way.     
#                                                                               
# Since: 2.8.0                                                                  
##

Think it's all about guarantees.

> +{ 'enum': 'CpuModelCompareResult',
> +  'data': [ 'incompatible', 'identical', 'superset', 'subset' ] }
> +
> +##
> +# @CpuModelCompareInfo
> +#
> +# The result of a CPU model comparison.
> +#
> +# @result: The result of the compare operation.
> +# @responsible-properties: List of properties that led to the comparison result
> +#                          not being identical.
> +#
> +# @responsible-properties is a list of QOM property names that led to
> +# both CPUs not being detected as identical. For identical models, this
> +# list is empty.
> +# If a QOM property is read-only, that means there's no known way to make the
> +# CPU models identical. If the special property name "type" is included, the
> +# models are by definition not identical and cannot be made identical.
> +#
> +# Since: 2.8.0
> +##
> +{ 'struct': 'CpuModelCompareInfo',
> +  'data': {'result': 'CpuModelCompareResult',
> +           'responsible-properties': ['str']
> +          }
> +}
> +
> +##
> +# @query-cpu-model-comparison:
> +#
> +# Compares two CPU models, returning how they compare under a specific QEMU
> +# machine.
> +#
> +# Note: This interface should not be used when global properties of CPU classes
> +#       are changed (e.g. via "-cpu ...").
> +#
> +# s390x supports comparing of all CPU models. Other architectures are not
> +# supported yet.
> +#
> +# Returns: a CpuModelBaselineInfo. Returns an error if comparing CPU models is
> +#          not supported, if a model cannot be used, if a model contains
> +#          an unknown cpu definition name, unknown properties or properties
> +#          with wrong types.
> +#
> +# Since: 2.8.0
> +##

This comment is now:

##                                                                              
# @query-cpu-model-comparison:                                                  
#                                                                               
# Compares two CPU models, returning how they compare in a specific             
# configuration. The results indicates how both models compare regarding        
# runnability. This result can be used by tooling to make decisions if a        
# certain CPU model will run in a certain configuration or if a compatible      
# CPU model has to be created by baselining.                                    
#                                                                               
# Usually, a CPU model is compared against the maximum possible CPU model       
# of a ceratin configuration (e.g. the "host" model for KVM). If that CPU       
# model is identical or a subset, it will run in that configuration.            
#                                                                               
# The result returned by this command may be affected by:                       
#                                                                               
# * QEMU version: CPU models may look different depending on the QEMU version.  
#   (Except for CPU models reported as "static" in query-cpu-definitions.)      
# * machine-type: CPU model  may look different depending on the machine-type.  
#   (Except for CPU models reported as "static" in query-cpu-definitions.)      
# * machine options (including accelerator): in some architectures, CPU models  
#   may look different depending on machine and accelerator options. (Except for
#   CPU models reported as "static" in query-cpu-definitions.)                  
# * "-cpu" arguments and global properties: arguments to the -cpu option and    
#   global properties may affect expansion of CPU models. Using                 
#   query-cpu-model-expansion while using these is not advised.                 
#                                                                               
# Some architectures may not support comparing CPU models. s390x supports       
# comparing CPU models.                                                         
#                                                                               
# Returns: a CpuModelBaselineInfo. Returns an error if comparing CPU models is  
#          not supported, if a model cannot be used, if a model contains        
#          an unknown cpu definition name, unknown properties or properties     
#          with wrong types.                                                    
#                                                                               
# Since: 2.8.0                                                                  
##  

(excluding the remark about s390x in this patch)

David