Re: [Xen-devel] [PATCH 04/27] x86/cpuid: Move featuresets into struct cpuid_policy

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.01.17 at 13:39, <andrew.cooper3@xxxxxxxxxx> wrote:
> +static void __init calculate_host_policy(void)
>  {
> -    unsigned int max, tmp;
> -
> -    max = cpuid_eax(0);
> -
> -    if ( max >= 1 )
> -        cpuid(0x1, &tmp, &tmp,
> -              &raw_featureset[FEATURESET_1c],
> -              &raw_featureset[FEATURESET_1d]);
> -    if ( max >= 7 )
> -        cpuid_count(0x7, 0, &tmp,
> -                    &raw_featureset[FEATURESET_7b0],
> -                    &raw_featureset[FEATURESET_7c0],
> -                    &raw_featureset[FEATURESET_7d0]);
> -    if ( max >= 0xd )
> -        cpuid_count(0xd, 1,
> -                    &raw_featureset[FEATURESET_Da1],
> -                    &tmp, &tmp, &tmp);
> -
> -    max = cpuid_eax(0x80000000);
> -    if ( (max >> 16) != 0x8000 )
> -        return;
> +    struct cpuid_policy *p = &host_policy;
>  
> -    if ( max >= 0x80000001 )
> -        cpuid(0x80000001, &tmp, &tmp,
> -              &raw_featureset[FEATURESET_e1c],
> -              &raw_featureset[FEATURESET_e1d]);
> -    if ( max >= 0x80000007 )
> -        cpuid(0x80000007, &tmp, &tmp, &tmp,
> -              &raw_featureset[FEATURESET_e7d]);
> -    if ( max >= 0x80000008 )
> -        cpuid(0x80000008, &tmp,
> -              &raw_featureset[FEATURESET_e8b],
> -              &tmp, &tmp);
> +    memcpy(p->fs, boot_cpu_data.x86_capability, sizeof(p->fs));

What are the plans for keeping this up-to-date wrt later
adjustments to boot_cpu_data.x86_capability? Wouldn't it be
better for the field to be a pointer, and the above to be a simple
assignment of &boot_cpu_data.x86_capability?

> +static void __init calculate_pv_max_policy(void)
>  {
> +    struct cpuid_policy *p = &pv_max_policy;

I assume later patches will add further uses of this variable?
Otherwise ...

> @@ -185,10 +159,12 @@ static void __init calculate_pv_featureset(void)
>      __set_bit(X86_FEATURE_CMP_LEGACY, pv_featureset);
>  
>      sanitise_featureset(pv_featureset);
> +    cpuid_featureset_to_policy(pv_featureset, p);

... using &pv_max_policy directly here would seem more friendly
to readers.

Jan


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