THE VF STATE MACHINE(9)

💅 The VF state machine

okay so welcome to The VF state machine(9) from the Kernel API Manual — yes bestie, we are doing state-machine lore today and it’s genuinely iconic 🎀

the simplified VF state machine can be drawn like this, no cap:

                           pause--------------------------o
                          /                               |
                         /                                v
                  (READY)<------------------resume-----(PAUSED)
                     ^                                /    /
                     |                               /    /
                     |     stop---->(STOPPED)<----stop    /
                     |                  /                /
                     |                 /                /
                     o--------<-----flr                /
                                                     /
                       o------<--------------------flr

where the cast is:

• READY — a state where the VF is fully operable. main character energy, everything works ✨
• PAUSED — a state where VF activity is temporarily suspended. it’s on a little break, not gone 💅
• STOPPED — a state where VF activity is definitely halted. like fully logged off, periodt.
• pause — a request to temporarily suspend VF activity.
• resume — a request to resume VF activity.
• stop — a request to definitely halt VF activity.
• flr — a request to perform VF FLR to restore VF activity. yes that’s the whole vibe 🦋

but bestie, each state transition is not just a little walk in the park — it requires extra steps that involve communication with GuC, and those steps might fail or be interrupted by other requests. so here’s the WIP diagram, and it’s giving very intricate:

                               .................................WIP....
                               :                                      :
                      pause--------------------->PAUSE_WIP----------------------------o
                     /         :                /                    :               |
                    /          :    o----<---stop          flr--o     :               |
                   /           :    |                    /     |     :               V
            (READY,RESUMED)<--------+------------RESUME_WIP<----+--<-----resume--(PAUSED)
              ^              :    |                           |     :          /   /
              |              :    |                           |     :         /   /
              |              :    |                           |     :        /   /
              |              :    o----<----------------------+--<-------stop   /
              |              :    |                           |     :          /
              |              :    V                           |     :         /
              |         stop----->STOP_WIP---------flr--->-----o     :        /
              |               :    |                           |     :       /
              |               :    |                           V     :      /
              |          flr--------+----->----------------->FLR_WIP<-----flr
              |                :    |                        /  ^     :
              |                :    |                       /   |     :
              o--------<-------:----+-----<----------------o    |     :
                               :    |                           |     :
                               :....|...........................|.....:
                                    |                           |
                                    V                           |
                                 (STOPPED)--------------------flr

for details about each internal WIP state machine, see:

• The VF PAUSE state machine_
• The VF RESUME state machine_
• The VF STOP state machine_
• The VF FLR state machine_

👀 SEE ALSO

Kernel file ./drivers/gpu/drm/xe/xe_gt_sriov_pf_control.c — yes, that’s the file, bestie 🫶

• The VF PAUSE state machine(9)
• xe_gt_sriov_pf_control_pause_vf(9)
• The VF RESUME state machine(9)
• xe_gt_sriov_pf_control_resume_vf(9)
• The VF SAVE state machine(9)
• xe_gt_sriov_pf_control_check_save_data_done(9)
• xe_gt_sriov_pf_control_check_save_failed(9)
• xe_gt_sriov_pf_control_process_save_data(9)
• xe_gt_sriov_pf_control_trigger_save_vf(9)
• xe_gt_sriov_pf_control_finish_save_vf(9)
• The VF RESTORE state machine(9)
• xe_gt_sriov_pf_control_check_restore_failed(9)
• xe_gt_sriov_pf_control_restore_data_done(9)
• xe_gt_sriov_pf_control_process_restore_data(9)
• xe_gt_sriov_pf_control_trigger_restore_vf(9)
• xe_gt_sriov_pf_control_finish_restore_vf(9)
• The VF STOP state machine(9)
• xe_gt_sriov_pf_control_stop_vf(9)
• The VF FLR state machine(9)
• xe_gt_sriov_pf_control_prepare_flr(9)
• xe_gt_sriov_pf_control_trigger_flr(9)
• xe_gt_sriov_pf_control_sync_flr(9)
• xe_gt_sriov_pf_control_wait_flr(9)
• The VF FLR Flow with GuC(9)
• xe_gt_sriov_pf_control_process_guc2pf(9)
• xe_gt_sriov_pf_control_init(9)
• xe_gt_sriov_pf_control_restart(9)

okay that’s the whole page, bestie 💖 final footer vibe: source/version ./drivers/gpu/drm/xe, date October 2026, and the page title is The VF state machine(9). periodt ✨