STRUCT PP_HEADER(9)

💖 struct pp_header(9) — the SST-PP header, explained 💖

okay so bestie, welcome to the Kernel API Manual entry for struct pp_header(9). this is genuinely the cutest little bitfield blob and i'm obsessed 🎀

It's the SST-PP (Perf profile) header — like, the little label on the front of the box that tells you what's inside. no cap ✨

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🌈 SYNOPSIS 🌈

here's the whole vibe, verbatim, do NOT touch:

struct pp_header {
    u64 feature_id :4;
    u64 feature_rev :8;
    u64 level_en_mask :8;
    u64 allowed_level_mask :8;
    u64 reserved0 :4;
    u64 ratio_unit :2;
    u64 block_size :8;
    u64 dynamic_switch :1;
    u64 memory_ratio_unit :2;
    u64 reserved1 :19;
 };

look at her. every field is a u64 with a lil colon number. she's packed, she's precise, she's main character energy 💅

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✨ Members ✨

• feature_id — 0=SST-CP, 1=SST-PP, 2=SST-BF, 3=SST-TF. it's giving "which feature am i" energy 🦋
• feature_rev — the Interface Version number for this SST feature. version check, periodt 🌸
• level_en_mask — the SST-PP level enable/disable fuse mask 🔥
• allowed_level_mask — the Allowed level mask used for dynamic config level switching 👑
• reserved0 — Reserved for future use. she's just holding space 💀
• ratio_unit — Frequency ratio unit. 00: 100MHz. All others are reserved. ngl this is the important one 🫶
• block_size — Size of PP block in Qword unit (8 bytes). lowkey a chunky girlie 😭
• dynamic_switch — If set (1), dynamic switching of SST PP is supported ⭐
• memory_ratio_unit — Memory Controller frequency ratio unit. 00: 100MHz, others reserved 💜
• reserved1 — Reserved for future use. another reserved icon, we stan 🙈

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🦋 Description 🦋

This structure is used store SST-PP header — and this is big — it's packed to the same format as defined in the specifications. so like, do not go rearranging her fields, bestie, the spec said what it said 💅

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💖 SEE ALSO 💖

• Kernel file
• ./drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c struct sst_header(9), struct cp_header(9), struct feature_offset(9), struct levels_offset(9), struct pp_control_offset(9), struct pp_status_offset(9), struct perf_level(9), struct tpmi_per_power_domain_info(9), struct tpmi_sst_struct(9), struct tpmi_sst_common_struct(9), map_cdies(9), map_partition_power_domain_id(9)

go read the whole squad, they're all in the same friend group fr fr 🧚

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okay that's the page!! this tea was served fresh from ./drivers/platform/x86/intel/s... 🍓 and it's dated October 2026 — yes, from the future, don't ask 💀 slay, go read your bitfields, ily, bye!! 🎀✨💜