enricobuehler
1271fd5ea2
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>
91 lines
5.7 KiB
Markdown
91 lines
5.7 KiB
Markdown
# Session-aware host — known limitations & follow-ups
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> **Status:** Session detection SHIPPED — host auto-detects the live session (Gaming / KDE / GNOME /
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> wlroots) **per connect** and routes video+input at it; opt-in mid-stream switch watcher
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> (`PUNKTFUNK_SESSION_WATCH=1`). Code: `crates/punktfunk-host/src/vdisplay.rs` +
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> `vdisplay/linux/{gamescope,kwin,mutter}.rs`. Items #2 + #3 resolved in code (`3363576`); this doc is
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> trimmed to the still-open limitations + their design rationale.
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The host auto-detects the live session per connect and routes both video and input at it — managed
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gamescope at the client's resolution in Steam Gaming Mode, a KWin/Mutter virtual output at the
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client's resolution on a Desktop. A watcher (opt-in: `PUNKTFUNK_SESSION_WATCH=1`) follows a
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Gaming↔Desktop switch **mid-stream** and rebuilds the backend in place without a reconnect.
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Live-validated on the Bazzite F44 box (`bazzite-deck-nvidia:testing`, RTX 4090): Desktop KDE at
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5120×1440 + input; Gaming managed at 5120×1440; warm-session reuse on quick reconnect; Feature B
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video-switch both directions.
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(Resolved: **#2 mid-stream-switch input** — `vdisplay::settle_desktop_portal()`; **#3 KWin/Mutter
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virtual output primary** — `apply_session_env` defaults `PUNKTFUNK_KWIN_VIRTUAL_PRIMARY` /
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`PUNKTFUNK_MUTTER_VIRTUAL_PRIMARY` on for the auto desktop path. Both shipped in `3363576`; details in
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git history.)
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> **Update 2026-07-05:** items **#1** (SIGKILL teardown / keep-warm) and **#7** (restore-guard /
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> keep-warm interaction) are picked up by `design/gamemode-and-dedicated-sessions.md` **Part A3**
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> — the managed session's restore becomes registry-owned and policy-driven (`keep_alive` replaces
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> the hardcoded 5 s debounce; "keep warm" = `keep_alive: forever`), with the SIGKILL-teardown
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> experiment folded into that stage's validation. That doc also covers the display-management
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> registry's game-mode conflicts (ownership classes, stale-node reuse) and dedicated per-launch
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> gamescope game sessions.
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## Still parked
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### 1. F44 gamescope teardown corrupts the GPU context
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Every gamescope teardown on this box (stop the autologin on connect; stop the managed session on
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restore) risks leaking the NVIDIA GPU context — surfaces as `CUDA_ERROR_ILLEGAL_STATE` (401) in
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`cuCtxCreate` / `vkCreateDevice` `VK_ERROR_INITIALIZATION_FAILED` (-3), then a black screen that
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**needs a reboot**. The 5 s debounced restore + the desktop restore-guard cut the teardown *count*
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but don't eliminate it. Options, in order of preference:
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- **SIGKILL the gamescope on teardown** instead of `systemctl stop` (SIGTERM). Hypothesis: skipping
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gamescope's buggy SIGTERM teardown handler (the part that SIGSEGVs, exit 139) lets the process die
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hard and the driver reclaim its GPU resources cleanly via normal process exit — no half-torn-down
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context. Change `stop_autologin_sessions` + `stop_session` (`vdisplay/linux/gamescope.rs`, both
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still use `systemctl --user stop` = SIGTERM) to `systemctl --user kill --signal=SIGKILL <unit>`
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(+ a follow-up `stop`/`reset-failed` to clear unit state). **Untested** — this is the first thing
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to try; it would preserve "managed client-res gaming AND TV-shows-gaming-when-idle".
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- **Keep the managed session warm** (no per-disconnect restore): spawn once, reuse forever, never
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tear down → ~1 teardown per host lifetime. Tradeoff: the TV is blank/idle when no client is
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connected (the autologin is never restored; return to gaming manually).
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- Upstream gamescope/driver fix.
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## Lower priority / polish
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### 4. Mid-stream-switch input loss window (~6 s)
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During the libei portal setup on a switch, buffered input drops (`libei: DROP — no resumed device`,
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hundreds of events). Polish: pre-warm the portal, or hold events instead of dropping during the
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device-resume window.
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### 5. NVENC `InitializeEncoder failed: invalid param` (recovered)
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At 5120×1440@240 the first NVENC open fails with `invalid param (8)` and **recovers** via the 2-way
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split-encode path (the stream is live). Cosmetic but noisy — investigate the first-attempt failure /
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silence the log.
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### 6. NVENC HEVC bitrate cap (~800 Mbps on the RTX 4090)
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HEVC opens at the GPU's max (~800 Mbps) when a higher rate is requested (e.g. 1600). Not a bug;
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consider preferring AV1 when the client requests >~800 Mbps HEVC, and surface the cap in the
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speed-test / bitrate UI.
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### 7. Restore-guard / keep-warm model interaction
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`do_restore_tv_session`, when a desktop is active, still stops the idle managed gamescope (a teardown
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— leak risk per #1) and consumes `STOPPED_AUTOLOGIN` (so a later return-to-gaming won't auto-restore
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the TV session). Resolve together with the keep-warm decision in #1.
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### 8. Feature B is opt-in
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The mid-stream watcher is gated behind `PUNKTFUNK_SESSION_WATCH=1` pending broader validation. Promote
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to default-on once #2 (mid-stream input) lands and it's exercised on more boxes.
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## Open items
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1. **F44 gamescope teardown corrupts the GPU context** (#1) — try SIGKILL on teardown
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(`stop_autologin_sessions` / `stop_session` in `vdisplay/linux/gamescope.rs`), else keep the
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managed session warm, else upstream fix.
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2. **Mid-stream-switch input-loss window (~6 s)** (#4) — pre-warm the portal or buffer/hold events
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instead of dropping during the device-resume window.
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3. **NVENC `InitializeEncoder failed: invalid param` noise at 5120×1440@240** (#5) — recovers via
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split-encode; investigate the first-attempt failure / silence the log.
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4. **NVENC HEVC ~800 Mbps cap on the RTX 4090** (#6) — consider preferring AV1 above it + surface the
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cap in the speed-test / bitrate UI.
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5. **Restore-guard / keep-warm interaction** (#7) — couples to #1; resolve together.
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6. **Feature B (`PUNKTFUNK_SESSION_WATCH`) still opt-in** (#8) — promote to default-on after #2 lands
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and it's exercised on more boxes.
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