Re: [PATCH 14/21] libs/guest: introduce helper to check cpu policy compatibility

[Jan Beulich <jbeulich@xxxxxxxx>]

On 23.03.2021 10:58, Roger Pau Monne wrote:
> --- a/tools/libs/guest/xg_cpuid_x86.c
> +++ b/tools/libs/guest/xg_cpuid_x86.c
> @@ -1098,3 +1098,20 @@ int xc_cpu_policy_update_msrs(xc_interface *xch, 
> xc_cpu_policy_t policy,
>      return rc;
>  
>  }
> +
> +bool xc_cpu_policy_is_compatible(xc_interface *xch, const xc_cpu_policy_t p1,
> +                                 const xc_cpu_policy_t p2)
> +{
> +    struct cpu_policy_errors err;

Don't you need an initializer here for ...

> +    int rc = x86_cpu_policies_are_compatible(p1, p2, &err);
> +
> +    if ( !rc )
> +        return true;
> +
> +    if ( err.leaf != -1 )
> +        ERROR("Leaf %#x subleaf %#x is not compatible", err.leaf, 
> err.subleaf);
> +    if ( err.msr != -1 )
> +        ERROR("MSR index %#x is not compatible", err.msr);

... these checks to have a chance of actually triggering? (I'm also
not certain -1 is a good indicator, but I guess we have been using it
elsewhere as well.)

Jan