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fix(whp-gui): WLR_LIBINPUT_NO_DEVICES=1 — root-cause the intermittent WHP GUI boot race #122

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Merged
TimLai666 merged 1 commit into from
Jul 10, 2026
Merged

fix(whp-gui): WLR_LIBINPUT_NO_DEVICES=1 — root-cause the intermittent WHP GUI boot race #122

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59 changes: 51 additions & 8 deletions crates/guest-agent/src/gui.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,22 @@ use anyhow::{Context, Result, bail};
use chefer_bundle::Manifest;
use nix::mount::{MsFlags, mount};

/// 記一行 GUI 診斷。同時走 stderr（原生 Linux / 有接 console 的後端可見）與 **`/dev/kmsg`**
/// ——WHP 的序列 console 在 `quiet` 下不顯示 guest-agent 自己的 stderr，但高優先序 kmsg 會
/// 出現在 console（同 appliance init 的 `report()`），故 WHP GUI 的啟動診斷才看得到。best-effort。
fn note(msg: &str) {
eprintln!("[guest-agent] gui: {msg}");
if let Ok(mut f) = std::fs::OpenOptions::new().write(true).open("/dev/kmsg") {
use std::io::Write as _;
// **一次 write() = 一筆 kmsg 記錄**：必須先組好整行再單次寫入。`writeln!`（write_fmt）
// 會拆成多次 write，只有第一筆帶 `<2>` 前綴、其餘（含訊息本體）落回預設 level 而被
// `quiet` 擋掉。`quiet` 把 console_loglevel 壓到 4（只印 level < 4），故用 <2>=KERN_CRIT
//（appliance init 的 report() 用 <0> 亦同理）。
let line = format!("<2>[guest-agent] gui: {msg}\n");
let _ = f.write_all(line.as_bytes());
}
}

/// cage 建立 Wayland socket 的 runtime 目錄（guest 內，appliance tmpfs 上）。
const GUI_RUNTIME_DIR: &str = "/run/chefer-gui";
/// 等 compositor socket 出現的上限。llvmpipe 首次啟動慢，放寬一點。
Expand Down Expand Up @@ -82,11 +98,13 @@ pub fn maybe_start(bundle_dir: &Path, manifest: &Manifest) -> Result<Option<GuiS
);
}

eprintln!("[guest-agent] gui: mounting the GUI overlay (cage/Xwayland/Mesa squashfs) …");
note("mounting the GUI overlay (cage/Xwayland/Mesa squashfs) …");
mount_overlay(&overlay).context("failed to mount the GUI overlay")?;

note("starting udev + seatd");
let udevd = start_udev();
let seatd = start_seatd();
note("starting cage");
let cage = start_cage().context("failed to start the in-VM compositor (cage)")?;
let mut session = GuiSession {
cage,
Expand Down Expand Up @@ -115,7 +133,7 @@ pub fn maybe_start(bundle_dir: &Path, manifest: &Manifest) -> Result<Option<GuiS
"[guest-agent] gui: Xwayland socket not present; X11-only apps will not find a DISPLAY (Wayland apps are unaffected)"
);
}
eprintln!("[guest-agent] gui: compositor ready (WAYLAND_DISPLAY=wayland-0)");
note("compositor ready (WAYLAND_DISPLAY=wayland-0)");
// compositor 就緒後起剪貼簿同步（env 已設好，wl-clipboard 可接 cage）。無 cmdline
// token（host 未啟用剪貼簿）或 wl-clipboard 缺失時回 None，不致命。
session.clipboard = crate::clipboard::maybe_start();
Expand Down Expand Up @@ -328,9 +346,16 @@ fn start_cage() -> Result<Child> {
.env("XDG_RUNTIME_DIR", GUI_RUNTIME_DIR)
.env("WLR_RENDERER", "pixman") // VM 無 GPU：強制軟算繪，避免 GLES 探測失敗
.env("LIBSEAT_BACKEND", "seatd") // Alpine libseat 無 builtin backend → 走 seatd
// 實機根因（WHP GUI 約 1/3 間歇失敗）：virtio-input 節點（/dev/input/event*）由 udev
// 非同步建立，cage 若早於 udev 啟動，wlroots 的 libinput backend 見「no input devices」
// 直接 abort → cage 秒退。wlroots 的錯誤訊息本身建議設此旗標容忍 0 輸入裝置啟動
//（裝置隨後由 udev 熱插拔補上），消除此競態。
.env("WLR_LIBINPUT_NO_DEVICES", "1")
.stdin(Stdio::null())
// cage/wlroots 的啟動失敗原因（缺 DRM、keymap…）只會出現在 stderr——
// 沿用 guest-agent stderr（VM console/診斷通道），別吞掉。
// cage/wlroots 的啟動失敗原因（缺 DRM、keymap、seatd…）只會出現在 stderr——**捕獲**
// 起來，cage 若啟動失敗（wait_for_socket 偵測）就轉發到 /dev/kmsg（WHP console 可見；
// 否則在 `quiet` 下這段錯誤完全看不到，見 note()）。
.stderr(Stdio::piped())
.spawn()?;
Ok(child)
}
Expand All @@ -343,11 +368,29 @@ fn wait_for_socket(sock: &Path, session: &mut GuiSession) -> Result<()> {
return Ok(());
}
if let Some(status) = session.cage.try_wait()? {
// cage 啟動失敗——把它捕獲的 stderr 轉到 kmsg（WHP console 可見），這正是
// 「Found 0 GPUs」/ seatd / keymap 之類真正原因的所在，否則在 quiet 下看不到。
let mut cage_err = String::new();
if let Some(mut err) = session.cage.stderr.take() {
use std::io::Read as _;
let _ = err.read_to_string(&mut cage_err);
}
let cage_err = cage_err.trim();
if !cage_err.is_empty() {
for line in cage_err.lines() {
note(&format!("cage: {line}"));
}
}
bail!(
"the in-VM compositor (cage) exited during startup ({status}); \
GUI cannot be shown. Check the guest log for wlroots errors \
(missing /dev/dri usually means the appliance kernel lacks virtio-gpu, \
or the VM host did not attach a virtio-gpu device)."
"the in-VM compositor (cage) exited during startup ({status}); GUI cannot be shown. \
cage stderr: {}. \
(missing /dev/dri usually means the appliance kernel lacks virtio-gpu, or the VM \
host did not attach a virtio-gpu device.)",
if cage_err.is_empty() {
"(none captured)"
} else {
cage_err
}
);
}
if start.elapsed() > SOCKET_WAIT {
Expand Down
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