Re: [PATCH v2 2/2] x86/cpuid: support LFENCE always serializing CPUID bit

[Jan Beulich <jbeulich@suse.com>]

On 20.04.2021 12:47, Roger Pau Monné wrote:
> On Tue, Apr 20, 2021 at 12:35:54PM +0200, Jan Beulich wrote:
>> I'd like to give Andrew a day or two more to respond there in case he
>> continues to see an issue, before I commit that with your R-b and this
>> one here. I'll assume you'll subsequently take care of that missing
>> piece then - if not, i.e. if e.g. I should, please let me know.
> 
> I think it should be something like the above,

Right (assuming you meant "below).

> in fact I think it
> would be perfectly fine to merge that chunk into your patch?

I'd rather not, so that this change can have its own reasoning in its
description.

Jan

> diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
> index 050cd5713e2..daf501779fe 100644
> --- a/xen/arch/x86/cpuid.c
> +++ b/xen/arch/x86/cpuid.c
> @@ -314,12 +314,9 @@ static void __init calculate_host_policy(void)
>  
>      *p = raw_cpuid_policy;
>  
> -    p->basic.max_leaf =
> -        min_t(uint32_t, p->basic.max_leaf,   ARRAY_SIZE(p->basic.raw) - 1);
> -    p->feat.max_subleaf =
> -        min_t(uint32_t, p->feat.max_subleaf, ARRAY_SIZE(p->feat.raw) - 1);
> -    p->extd.max_leaf = 0x80000000 | min_t(uint32_t, p->extd.max_leaf & 0xffff,
> -                                          ARRAY_SIZE(p->extd.raw) - 1);
> +    p->basic.max_leaf = ARRAY_SIZE(p->basic.raw) - 1;
> +    p->feat.max_subleaf = ARRAY_SIZE(p->feat.raw) - 1;
> +    p->extd.max_leaf = 0x80000000 | ARRAY_SIZE(p->extd.raw) - 1;
>  
>      cpuid_featureset_to_policy(boot_cpu_data.x86_capability, p);
>      recalculate_xstate(p);
>