enricobuehler
9775794ba5
Capture the deliberately-parked items after live-validating the session-aware backend selector on the Bazzite F44 box (Desktop KDE + Gaming both at the client's resolution, warm reuse, Feature B mid-stream switch both directions). Top follow-ups: (1) F44 gamescope teardown corrupts the GPU context (try SIGKILL teardown, else keep the managed session warm); (2) mid-stream-switch input is flaky until a reconnect (portal opens before the systemd/D-Bus activation env settles — fix: import-environment on switch); (3) the KWin virtual output isn't set primary. Plus polish: input-loss window on switch, the recovered NVENC invalid-param log, the 4090 HEVC ~800Mbps cap, restore-guard/keep-warm interaction, and promoting Feature B from opt-in to default. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
5.2 KiB
Session-aware host — known limitations & follow-ups
Status: 2026-06-14. The host auto-detects the live session (Gaming / KDE / GNOME / wlroots) 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. The items below are deliberately parked — they have workarounds
and/or are F44-specific.
High priority
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. Changestop_autologin_sessions+stop_session(vdisplay/gamescope.rs) tosystemctl --user kill --signal=SIGKILL <unit>(+ a follow-upstop/reset-failedto 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.
2. Mid-stream-switch input (Gaming→Desktop) is flaky until a reconnect
After a mid-stream switch to a desktop, pointer/keyboard often don't land until a disconnect+reconnect.
Root cause: on the switch the host opens the KDE RemoteDesktop portal immediately, but the
portal is a D-Bus-activated service that reads the systemd --user activation environment, which
hasn't settled to the new session yet — so the portal session is created against a half-stale env. It
accepts events (no error, so the injector's reopen-on-failure never fires) but they don't reach
KDE. The host log even shows libei: portal granted devices + device RESUMED, yet input is dead.
Workaround: reconnect once after switching (re-opens the portal against the settled env → works).
Fix: on a session switch, push the new session env into the systemd/D-Bus activation environment
before reopening input — systemctl --user import-environment WAYLAND_DISPLAY XDG_CURRENT_DESKTOP DBUS_SESSION_BUS_ADDRESS + dbus-update-activation-environment (exactly what a fresh KDE login does;
see scripts/headless/run-headless-kde.sh:118-119) — and/or delay/retry the input reopen until the
portal is settled.
3. KWin virtual output is not set as primary
The KWin virtual output isn't marked the primary display, so KDE panels / primary-screen content can
stay on the (now-absent) original output instead of the streamed virtual screen. Follow-up: set the
virtual output primary on create — vdisplay/kwin.rs already reads PUNKTFUNK_KWIN_VIRTUAL_PRIMARY;
make it default-on (or always promote the new output to primary via the KWin/kscreen API) so the
streamed screen is the primary desktop.
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.