STRUCT SVSM_VTPM_CMD_REQUEST(9)

🎀 struct svsm_vtpm_cmd_request(9) 🎀

okay so bestie, welcome to the Kernel API Manual — yes we're literally reading kernel docs together, this is our friendship era 💖 and today's main character is this struct, no cap.

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✨ NAME ✨

struct svsm_vtpm_cmd_request — the structure you use for a TPM_SEND_COMMAND request. that's it, that's the vibe 🫶

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🌸 SYNOPSIS 🌸

struct svsm_vtpm_cmd_request {
    u32 cmd;
    u8 locality;
    u32 buf_size;
    u8 buf[];
 };

like look at her. iconic layout. lowkey obsessed 💅

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💜 MEMBERS 💜

• cmd — the command you're sending, and heads up: it must be TPM_SEND_COMMAND. not optional, not vibes-based, just that one 🔥
• locality — the locality. that's the whole description bestie, she's mysterious like that 🧚
• buf_size — the size of the input buffer that follows ✨
• buf — a buffer of size buf_size. so like, exactly as big as you said it was 🙈

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🦋 DESCRIPTION 🦋

this whole thing is defined by the AMD SVSM spec [1], in the section "8.2 SVSM_VTPM_CMD Call" — Table 16: TPM_SEND_COMMAND Request Structure. and because tables are not the moment here, let me lay the bytes out for you, one icon at a time:

• Byte Offset 0x000 — Size (Bytes) 4 — Meaning: Platform command (8)
• Byte Offset 0x004 — Size (Bytes) 1 — Meaning: Locality (must-be-0)
• Byte Offset 0x005 — Size (Bytes) 4 — Meaning: TPM Command size (in bytes)
• Byte Offset 0x009 — Size (Bytes) Variable — Meaning: TPM Command

see? 0x000 → 0x004 → 0x005 → 0x009. the way the offsets just line up, it's giving organized queen 👑

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⭐ NOTE ⭐

real talk bestie, the TCG Simulator expects buf_size to be equal to the size of the specific TPM command. if you fudge it, you get a TPM_RC_COMMAND_SIZE error back. so like… don't do that 💀

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🌈 SEE ALSO 🌈

• Kernel file ./include/linux/tpm_svsm.h (the source of truth, go visit her)
• struct svsm_vtpm_request(9)
• struct svsm_vtpm_response(9)
• struct svsm_vtpm_cmd_response(9)
• svsm_vtpm_cmd_request_fill(9)
• svsm_vtpm_cmd_response_parse(9)

the whole friend group honestly, go read all of them 🍓

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and that's the page! sourced from ./include/linux, dated October 2026, filed under struct svsm_..._cmd_request(9) — mwah, love u, go write some TPM commands responsibly 💖✨🎀