Re: [RFC PATCH for-4.22 v2 1/3] x86/cpu-policy: Infrastructure for CPUID leaf 0x6

["Teddy Astie" <teddy.astie@xxxxxxxxxx>]

Le 30/10/2025 à 08:14, Jan Beulich a écrit :
> On 29.10.2025 16:59, Teddy Astie wrote:
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Signed-off-by: Teddy Astie <teddy.astie@xxxxxxxxxx>
>> ---
>> v2: introduced
>
> This being a change of mine, I'm not happy for the title to have changed, and
> for the (little bit of) description to have been dropped.
>
>> --- a/xen/include/xen/lib/x86/cpu-policy.h
>> +++ b/xen/include/xen/lib/x86/cpu-policy.h
>> @@ -121,7 +121,32 @@ struct cpu_policy
>>               uint64_t :64, :64; /* Leaf 0x3 - PSN. */
>>               uint64_t :64, :64; /* Leaf 0x4 - Structured Cache. */
>>               uint64_t :64, :64; /* Leaf 0x5 - MONITOR. */
>> -            uint64_t :64, :64; /* Leaf 0x6 - Therm/Perf. */
>> +
>> +            /* Leaf 0x6 - Therm/Perf. */
>> +            struct {
>> +                uint32_t /* a */
>> +                    dts:1,
>> +                    turbo:1,
>> +                    arat:1,
>> +                    :4,
>> +                    hwp:1,
>> +                    hwp_notification:1,
>> +                    hwp_activity_window:1,
>> +                    hwp_epp:1,
>> +                    hwp_plr:1,
>> +                    :1,
>> +                    hdc:1,
>> +                    :2,
>> +                    hwp_peci:1,
>> +                    :2,
>> +                    hw_feedback:1,
>> +                    :12;
>> +                uint32_t /* b */:32;
>> +                uint32_t /* c */ aperfmperf:1,
>> +                    :31;
>> +                uint32_t /* d */:32;
>> +            } pm;
>> +
>>               uint64_t :64, :64; /* Leaf 0x7 - Structured Features. */
>>               uint64_t :64, :64; /* Leaf 0x8 - rsvd */
>>               uint64_t :64, :64; /* Leaf 0x9 - DCA */
>
> As I had said, this (really: the use of these bits in the host policy) 
> actually
> requires an adjustment to cpu-policy.c as well, which I'm carrying as a 
> separate,
> prereq change (re-produced below). May I suggest that your work go on top of 
> mine
> (which I'll post once we have branched 4.21 off)?
>

I'm ok with it.

> Jan
>
> x86/cpu-policy: move invocation of recalculate_misc()
>
> The function is about guest exposure of features / leaves. There's no need
> for it to be applied on the host policy. In fact doing so gets in the way
> of using the host policy in certain places.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> --- a/xen/arch/x86/cpu-policy.c
> +++ b/xen/arch/x86/cpu-policy.c
> @@ -424,7 +424,6 @@ void __init calculate_host_policy(void)
>       x86_cpu_featureset_to_policy(boot_cpu_data.x86_capability, p);
>       recalculate_xstate(p);
>       recalculate_tile(p);
> -    recalculate_misc(p);
>
>       /* When vPMU is disabled, drop it from the host policy. */
>       if ( vpmu_mode == XENPMU_MODE_OFF )
> @@ -705,6 +704,7 @@ static void __init calculate_pv_max_poli
>       unsigned int i;
>
>       *p = host_cpu_policy;
> +    recalculate_misc(p);
>
>       guest_common_max_leaves(p);
>
> @@ -809,6 +809,7 @@ static void __init calculate_hvm_max_pol
>       const uint32_t *mask;
>
>       *p = host_cpu_policy;
> +    recalculate_misc(p);
>
>       guest_common_max_leaves(p);
>
>
>

Teddy


--
Teddy Astie | Vates XCP-ng Developer

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