Re: [Xen-devel] [PATCH] x86/cpuid: Move vendor/family/model information from arch_domain to cpuid_policy

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.01.17 at 13:32, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -78,12 +78,11 @@ static void update_domain_cpuid_info(struct domain *d,
>      switch ( ctl->input[0] )
>      {
>      case 0: {
> -        int old_vendor = d->arch.x86_vendor;
> +        int old_vendor = p->x86_vendor;
>  
> -        d->arch.x86_vendor = get_cpu_vendor(
> -            ctl->ebx, ctl->ecx, ctl->edx, gcv_guest);
> +        p->x86_vendor = get_cpu_vendor(ctl->ebx, ctl->ecx, ctl->edx, 
> gcv_guest);
>  
> -        if ( is_hvm_domain(d) && (d->arch.x86_vendor != old_vendor) )
> +        if ( is_hvm_domain(d) && (p->x86_vendor != old_vendor) )
>          {
>              struct vcpu *v;
>  
> @@ -95,7 +94,7 @@ static void update_domain_cpuid_info(struct domain *d,
>      }
>  
>      case 1:
> -        d->arch.x86 = get_cpu_family(ctl->eax, &d->arch.x86_model, NULL);
> +        p->x86_family = get_cpu_family(ctl->eax, &p->x86_model, NULL);
>  
>          if ( is_pv_domain(d) && ((levelling_caps & LCAP_1cd) == LCAP_1cd) )
>          {

Considering that the three fields can be calculated from other
CPUID data, is it really worthwhile to store these redundant pieces
of information, instead of having consumers simply call
get_cpu_{vendor,policy}()? All we "gain" by storing them is the risk
of them going out of sync.

Jan


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