VF2PF_HANDSHAKE(9)

💅 VF2PF_HANDSHAKE(9) ✨

okay bestie, buckle up — this is VF2PF_HANDSHAKE, straight out of the Kernel API Manual. it's a Relay Message, and it's giving ✨handshake protocol✨. it's how the VF and the PF figure out which ABI version they're gonna speak to each other. like matching outfits before you go out. iconic behavior honestly 🫶

---

🌸 the actual vibe 🌸

so, before the VF driver and the PF driver exchange literally any other messages, they must negotiate the VF/PF ABI version that'll be used in all their communication. no small talk first. negotiation first. periodt 💅

the VF driver uses the MAJOR and MINOR fields to pass along the ABI version it's requesting. and here's the cute part — the VF driver may use the special version 0.0 (that's both MAJOR and MINOR set to 0) to ask for the latest ABI version supported by the PF driver. or like, any version the PF supports. flexible queen energy 👑

🎀 important, no cap: this message definition shall be supported by all future ABI versions. and it shall not be changed by future ABI versions. locked in forever, iykyk.

---

📨 the REQUEST (VF → PF) 💌

Dword 0 — the header bits:

• 31 — ORIGIN = GUC_HXG_ORIGIN_HOST_
• 30:28 — TYPE = GUC_HXG_TYPE_REQUEST_
• 27:16 — DATA0 = MBZ
• 15:0 — ACTION = GUC_RELAY_ACTION_VF2PF_HANDSHAKE = 0x0001

Dword 1 — the version ask:

• 31:16 — MAJOR — requested major version of the VFPF interface (use MAJOR_ANY to request latest version supported by PF)
• 15:0 — MINOR — requested minor version of the VFPF interface (use MINOR_ANY to request latest version supported by PF)

---

📬 the RESPONSE (PF → VF) 🦋

Dword 0 — the header bits:

• 31 — ORIGIN = GUC_HXG_ORIGIN_HOST_
• 30:28 — TYPE = GUC_HXG_TYPE_RESPONSE_SUCCESS_
• 27:0 — DATA0 = MBZ

Dword 1 — the version they agreed on:

• 31:16 — MAJOR — agreed major version of the VFPF interface
• 15:0 — MINOR — agreed minor version of the VFPF interface

---

✨ SEE ALSO ✨

• kernel file ./drivers/gpu/drm/xe/abi/guc_relay_actions_abi.h
• GuC Relay VF/PF ABI Version(9)
• GuC Relay Actions(9)
• VF2PF_QUERY_RUNTIME(9)
• GuC Relay Debug Actions(9)
• VFXPF_TESTLOOP(9)

---

okay that's the whole thing, bestie — go forth and negotiate 🧚💜

mwah 💋 this came to you from ./drivers/gpu/drm/xe/abi, dated October 2026, filed under VF2PF_HANDSHAKE(9). bookmark it, screenshot it, tattoo it on your forearm, whatever 🌈⭐