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enricobuehler 1271fd5ea2 feat(host): game-mode integration + dedicated game sessions

Implements design/gamemode-and-dedicated-sessions.md (Parts A1-A5 + B0-B2):
reconciles the merged display-management registry with session-mobile
Bazzite/SteamOS hosts and adds a per-launch dedicated gamescope mode.

- A1 DisplayOwnership {Owned,External,SessionManaged} + poolable_now(): the
  registry pools only what it owns, so gamescope managed/attach outputs are no
  longer double-owned by the registry AND the gamescope restore worker (fixes
  the game-mode-reconnect stale-node wedge).
- A2 validated reuse: (backend,mode,launch,epoch) reuse key + kept_display_alive
  liveness probe + reused_gen/mark_failed on a reused-display first-frame failure.
- A3 policy-driven managed restore (keep_alive replaces the hardcoded 5s debounce;
  forever = held = gaming-rig truthful) + crash-restore persist + SIGKILL teardown
  (kill_unit, applied to our transient unit AND the autologin stop -- validated
  live on .181 to avoid the F44 GPU-context leak).
- A4 session epoch: observe_session_instance bumps the epoch + invalidate_backend
  on a desktop-compositor instance change; gamescope spawns are exempt.
- A5 per-spawn log + PID-scoped gamescope node discovery.
- B0 game_session {auto,dedicated} policy (top-level, preset-orthogonal) +
  pick_gamescope_mode dedicated_launch + steam -silent command shaping.
- B1 free the autologin Steam before a dedicated Steam spawn (single-instance).
- B2 game-exit -> APP_EXITED_CLOSE_CODE (0x52) clean session end.

Adversarially reviewed (11 findings fixed). Validated on glass (.181 Bazzite F44,
RTX 4090): dedicated spawn streams a real game smoothly; keep-alive reuse; the
SIGKILL fix avoids the F44 vkCreateDevice leak. Workspace green
(build / test --workspace / clippy -D warnings / fmt), OpenAPI + C header
regenerated, web console tsc + vite build green. clients/probe: bump the
no-video timeout 8s->45s for gamescope cold starts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-07-06 10:33:43 +00:00

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Session-aware host — known limitations & follow-ups

Status: Session detection SHIPPED — host auto-detects the live session (Gaming / KDE / GNOME / wlroots) per connect and routes video+input at it; opt-in mid-stream switch watcher (PUNKTFUNK_SESSION_WATCH=1). Code: crates/punktfunk-host/src/vdisplay.rs + vdisplay/linux/{gamescope,kwin,mutter}.rs. Items #2 + #3 resolved in code (3363576); this doc is trimmed to the still-open limitations + their design rationale.

The host auto-detects the live session per connect and routes both video and input at it — managed gamescope at the client's resolution in Steam Gaming Mode, a KWin/Mutter virtual output at the client's resolution on a Desktop. A watcher (opt-in: PUNKTFUNK_SESSION_WATCH=1) follows a Gaming↔Desktop switch mid-stream and rebuilds the backend in place without a reconnect.

Live-validated on the Bazzite F44 box (bazzite-deck-nvidia:testing, RTX 4090): Desktop KDE at 5120×1440 + input; Gaming managed at 5120×1440; warm-session reuse on quick reconnect; Feature B video-switch both directions.

(Resolved: #2 mid-stream-switch input — vdisplay::settle_desktop_portal(); #3 KWin/Mutter virtual output primary — apply_session_env defaults PUNKTFUNK_KWIN_VIRTUAL_PRIMARY / PUNKTFUNK_MUTTER_VIRTUAL_PRIMARY on for the auto desktop path. Both shipped in 3363576; details in git history.)

Update 2026-07-05: items #1 (SIGKILL teardown / keep-warm) and #7 (restore-guard / keep-warm interaction) are picked up by design/gamemode-and-dedicated-sessions.md Part A3 — the managed session's restore becomes registry-owned and policy-driven (keep_alive replaces the hardcoded 5 s debounce; "keep warm" = keep_alive: forever), with the SIGKILL-teardown experiment folded into that stage's validation. That doc also covers the display-management registry's game-mode conflicts (ownership classes, stale-node reuse) and dedicated per-launch gamescope game sessions.

Still parked

1. F44 gamescope teardown corrupts the GPU context

Every gamescope teardown on this box (stop the autologin on connect; stop the managed session on restore) risks leaking the NVIDIA GPU context — surfaces as CUDA_ERROR_ILLEGAL_STATE (401) in cuCtxCreate / vkCreateDevice VK_ERROR_INITIALIZATION_FAILED (-3), then a black screen that needs a reboot. The 5 s debounced restore + the desktop restore-guard cut the teardown count but don't eliminate it. Options, in order of preference:

SIGKILL the gamescope on teardown instead of systemctl stop (SIGTERM). Hypothesis: skipping gamescope's buggy SIGTERM teardown handler (the part that SIGSEGVs, exit 139) lets the process die hard and the driver reclaim its GPU resources cleanly via normal process exit — no half-torn-down context. Change stop_autologin_sessions + stop_session (vdisplay/linux/gamescope.rs, both still use systemctl --user stop = SIGTERM) to systemctl --user kill --signal=SIGKILL <unit> (+ a follow-up stop/reset-failed to clear unit state). Untested — this is the first thing to try; it would preserve "managed client-res gaming AND TV-shows-gaming-when-idle".
Keep the managed session warm (no per-disconnect restore): spawn once, reuse forever, never tear down → ~1 teardown per host lifetime. Tradeoff: the TV is blank/idle when no client is connected (the autologin is never restored; return to gaming manually).
Upstream gamescope/driver fix.

Lower priority / polish

4. Mid-stream-switch input loss window (~6 s)

During the libei portal setup on a switch, buffered input drops (libei: DROP — no resumed device, hundreds of events). Polish: pre-warm the portal, or hold events instead of dropping during the device-resume window.

5. NVENC `InitializeEncoder failed: invalid param` (recovered)

At 5120×1440@240 the first NVENC open fails with invalid param (8) and recovers via the 2-way split-encode path (the stream is live). Cosmetic but noisy — investigate the first-attempt failure / silence the log.

6. NVENC HEVC bitrate cap (~800 Mbps on the RTX 4090)

HEVC opens at the GPU's max (~800 Mbps) when a higher rate is requested (e.g. 1600). Not a bug; consider preferring AV1 when the client requests >~800 Mbps HEVC, and surface the cap in the speed-test / bitrate UI.

7. Restore-guard / keep-warm model interaction

do_restore_tv_session, when a desktop is active, still stops the idle managed gamescope (a teardown — leak risk per #1) and consumes STOPPED_AUTOLOGIN (so a later return-to-gaming won't auto-restore the TV session). Resolve together with the keep-warm decision in #1.

8. Feature B is opt-in

The mid-stream watcher is gated behind PUNKTFUNK_SESSION_WATCH=1 pending broader validation. Promote to default-on once #2 (mid-stream input) lands and it's exercised on more boxes.

Open items

F44 gamescope teardown corrupts the GPU context (#1) — try SIGKILL on teardown (stop_autologin_sessions / stop_session in vdisplay/linux/gamescope.rs), else keep the managed session warm, else upstream fix.
Mid-stream-switch input-loss window (~6 s) (#4) — pre-warm the portal or buffer/hold events instead of dropping during the device-resume window.
NVENC InitializeEncoder failed: invalid param noise at 5120×1440@240 (#5) — recovers via split-encode; investigate the first-attempt failure / silence the log.
NVENC HEVC ~800 Mbps cap on the RTX 4090 (#6) — consider preferring AV1 above it + surface the cap in the speed-test / bitrate UI.
Restore-guard / keep-warm interaction (#7) — couples to #1; resolve together.
Feature B (PUNKTFUNK_SESSION_WATCH) still opt-in (#8) — promote to default-on after #2 lands and it's exercised on more boxes.

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