Re: [PATCH v3 1/6] x86/cpu-policy: define bits of leaf 6

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

Le 14/01/2026 à 14:45, Jan Beulich a écrit :
> ... as far as we presently use them in the codebase.
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> Or should we make both parts proper featureset elements? At least
> APERFMPERF could likely be made visible to guests (in principle).
> ---
> v3: Use SDM-conforming names. (Sorry Jason, had to drop you R-b once
>      again.)
> v2: Use bool and unions.
>
> --- a/xen/include/xen/lib/x86/cpu-policy.h
> +++ b/xen/include/xen/lib/x86/cpu-policy.h
> @@ -121,7 +121,46 @@ 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. */
> +            union {
> +                uint32_t _6a;
> +                struct {
> +                    bool :1,
> +                        turbo_boost:1,
> +                        arat:1,
> +                        :1,
> +                        :1,
> +                        :1,
> +                        :1,
> +                        hwp:1,
> +                        hwp_interrupt:1,
> +                        hwp_activity_window:1,
> +                        hwp_epp:1,
> +                        hwp_request_pkg:1,
> +                        :1,
> +                        hdc:1,
> +                        :1,
> +                        :1,
> +                        hwp_peci_override:1,
> +                        :1,
> +                        :1,
> +                        hw_feedback:1;
> +                };
> +            };
> +            union {
> +                uint32_t _6b;
> +            };
> +            union {
> +                uint32_t _6c;
> +                struct {
> +                    bool hw_feedback_cap:1;
> +                };
> +            };
> +            union {
> +                uint32_t _6d;
> +            };
> +

While I'm ok for the a and c unions, I'm not convinced by the b and d
ones (union with just a single uint32_t in it) as it's quite verbose and
inconsistent with the rest of the cpu_policy structure.

>               uint64_t :64, :64; /* Leaf 0x7 - Structured Features. */
>               uint64_t :64, :64; /* Leaf 0x8 - rsvd */
>               uint64_t :64, :64; /* Leaf 0x9 - DCA */
>
>



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