Re: [PATCH 3/5] i386/kvm: Support event with select & umask format in KVM PMU filter

[Zhao Liu <zhao1.liu@intel.com>]

> > What I'm a bit hesitant about is that, if different arches add similar
> > "conditional" enumerations later, it could cause the enumeration values
> > to change under different compilation conditions (correct? :-)). Although
> > it might not break anything, since we don't rely on the specific numeric
> > values.
> 
> Every binary we create contains target-specific code for at most one
> target.  Therefore, different numerical encodings for different targets
> are fine.
> 
> Same argument for struct members, by the way.  Consider
> 
>     { 'struct': 'CpuModelExpansionInfo',
>       'data': { 'model': 'CpuModelInfo',
>                 'deprecated-props' : { 'type': ['str'],
>                                        'if': 'TARGET_S390X' } },
>       'if': { 'any': [ 'TARGET_S390X',
>                        'TARGET_I386',
>                        'TARGET_ARM',
>                        'TARGET_LOONGARCH64',
>                        'TARGET_RISCV' ] } }
> 
> This generates
> 
>     #if defined(TARGET_S390X) || defined(TARGET_I386) || defined(TARGET_ARM) || defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV)
>     struct CpuModelExpansionInfo {
>         CpuModelInfo *model;
>     #if defined(TARGET_S390X)
>         strList *deprecated_props;
>     #endif /* defined(TARGET_S390X) */
>     };
>     #endif /* defined(TARGET_S390X) || defined(TARGET_I386) || defined(TARGET_ARM) || defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV) */
> 
> The struct's size depends on the target.  If we ever add members after
> @deprecated_props, their offset depends on the target, too.

Thank your for further explanation!

Regards,
Zhao