feat(windows-drivers): host-gone watchdog, SET_RENDER_ADAPTER, log gate, mode bounds

Audit §4.1: implement the host-gone watchdog — it was dead code (WATCHDOG_PINGS bumped but never sampled, no thread). Every IOCTL now bumps a liveness counter; a watchdog thread reap_orphaned()s monitors (created_at grace) if no IOCTL arrives within WATCHDOG_TIMEOUT_S, so a crashed/TerminateProcess'd host no longer leaves its virtual monitor + swap-chain worker + pooled D3D device wedged until the next CLEAR_ALL. Removes the false 'watchdog thread' comments.

Audit §4.2: implement SET_RENDER_ADAPTER (was STATUS_NOT_IMPLEMENTED) via IddCxAdapterSetRenderAdapter, so the host can pin the IDD render to the NVENC GPU on a hybrid iGPU+dGPU box (else the OS-picked iGPU makes the host ring textures un-openable -> DRV_STATUS_TEX_FAIL).

Audit §4.4: gate the world-writable C:\Users\Public\pfvd-driver.log behind debug builds / PFVD_DEBUG_LOG (a release build never writes it).

Audit §4.5: bounds-check the requested mode in IOCTL_ADD; compute display_info clock_rate in u64 + saturate (the old u32 refresh*(h+4)^2 overflowed/aborted the mode DDI for large modes).

Verified: driver workspace builds clean on the RTX box (WDK 26100 + LLVM 21.1.2, MSVC). On-glass functional validation of the watchdog/render-pin is a follow-up (needs a driver reinstall + session).

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

packaging/windows/drivers/pf-vdisplay/src/adapter.rs

@@ -142,3 +142,26 @@ pub fn set_adapter(adapter: iddcx::IDDCX_ADAPTER) {
 pub(crate) fn adapter() -> Option<iddcx::IDDCX_ADAPTER> {
     ADAPTER.get().map(|a| a.0)
 }
+
+/// Honor the host's `IOCTL_SET_RENDER_ADAPTER`: pin the GPU the IddCx swap-chain renders on. On a hybrid
+/// iGPU+dGPU box the OS may otherwise pick the iGPU to render the virtual monitor, so the host's shared
+/// ring textures (created on the NVENC dGPU) can't be opened → `DRV_STATUS_TEX_FAIL` → the host's 20 s
+/// black bail. Pinning the render adapter to the encode GPU fixes that. Unconditional — NOT the
+/// SudoVDA-parity default-off branch (`docs/windows-host-rewrite-audit.md` §4.2). Returns
+/// `STATUS_NOT_FOUND` if called before the adapter exists.
+pub fn set_render_adapter(luid_low: u32, luid_high: i32) -> NTSTATUS {
+    let Some(adapter) = adapter() else {
+        return crate::STATUS_NOT_FOUND;
+    };
+    // SAFETY: building a C POD — the all-zero bit pattern is a valid IDARG_IN_ADAPTERSETRENDERADAPTER;
+    // the one meaningful field is assigned below.
+    let mut in_args: iddcx::IDARG_IN_ADAPTERSETRENDERADAPTER = unsafe { core::mem::zeroed() };
+    in_args.PreferredRenderAdapter = wdk_sys::LUID {
+        LowPart: luid_low,
+        HighPart: luid_high,
+    };
+    dbglog!("[pf-vd] set_render_adapter -> {luid_high:08x}:{luid_low:08x}");
+    // SAFETY: `adapter` is the stashed IddCx adapter; `in_args` is valid local storage read synchronously.
+    unsafe { wdk_iddcx::IddCxAdapterSetRenderAdapter(adapter, &in_args) };
+    STATUS_SUCCESS
+}

packaging/windows/drivers/pf-vdisplay/src/callbacks.rs

@@ -33,6 +33,7 @@ pub unsafe extern "C" fn adapter_init_finished(
 ) -> NTSTATUS {
     dbglog!("[pf-vd] adapter_init_finished");
     crate::adapter::set_adapter(adapter);
+    crate::control::start_watchdog();
     STATUS_SUCCESS
 }
 

packaging/windows/drivers/pf-vdisplay/src/control.rs

@@ -3,25 +3,76 @@
 //! (watchdog keepalive), ADD/REMOVE/CLEAR_ALL (virtual monitors), and SET_RENDER_ADAPTER (next). Every
 //! path completes the `WDFREQUEST` exactly once (the `EVT_IDD_CX_DEVICE_IO_CONTROL` shape returns `()`).
 
-use core::sync::atomic::{AtomicU64, Ordering};
+use core::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+use std::time::{Duration, Instant};
 
 use pf_vdisplay_proto::control;
 use wdk_iddcx::nt_success;
 use wdk_sys::{NTSTATUS, WDFREQUEST, call_unsafe_wdf_function_binding};
 
-use crate::{STATUS_INVALID_PARAMETER, STATUS_NOT_FOUND, STATUS_NOT_IMPLEMENTED, STATUS_SUCCESS};
+use crate::{STATUS_INVALID_PARAMETER, STATUS_NOT_FOUND, STATUS_SUCCESS};
 
-/// The host must PING within this window or the watchdog reaps all monitors (STEP 4: the watchdog thread).
+/// The host must send an IOCTL within this window (it PINGs on a `timeout/3` timer) or the watchdog
+/// treats it as gone and reaps every monitor. Reported to the host via [`control::IOCTL_GET_INFO`].
 const WATCHDOG_TIMEOUT_S: u32 = 10;
 
-/// Keepalive counter — PING bumps it; STEP 4's watchdog thread samples it to detect a gone host.
+/// Host-liveness counter — EVERY inbound IOCTL bumps it; [`start_watchdog`]'s thread samples it.
 static WATCHDOG_PINGS: AtomicU64 = AtomicU64::new(0);
+/// Spawns the watchdog thread exactly once (idempotent across re-entrant adapter inits).
+static WATCHDOG_STARTED: AtomicBool = AtomicBool::new(false);
+
+/// Start the host-liveness watchdog (once, from `adapter_init_finished`).
+///
+/// Previously [`WATCHDOG_PINGS`] was bumped but NEVER sampled (no thread existed) — so a host that died
+/// without a cooperative REMOVE (crash / `TerminateProcess`) left its virtual monitor + swap-chain
+/// worker + pooled D3D device wedged in WUDFHost until the next host start's CLEAR_ALL, and a
+/// not-restarted host left the orphan monitor in the desktop topology indefinitely
+/// (`docs/windows-host-rewrite-audit.md` §4.1). This thread closes that: if no IOCTL arrives for
+/// `WATCHDOG_TIMEOUT_S` while monitors exist, it departs them all.
+///
+/// (A WDF `EvtFileClose` on the control handle would be more immediate — the plan's preferred §3.4
+/// option — but the polling watchdog matches the proven oracle and needs no IddCx file-object plumbing.)
+pub fn start_watchdog() {
+    if WATCHDOG_STARTED.swap(true, Ordering::SeqCst) {
+        return;
+    }
+    let tick = Duration::from_secs(u64::from((WATCHDOG_TIMEOUT_S / 3).max(1)));
+    let timeout = Duration::from_secs(u64::from(WATCHDOG_TIMEOUT_S));
+    std::thread::spawn(move || {
+        let mut last = WATCHDOG_PINGS.load(Ordering::Relaxed);
+        let mut last_change = Instant::now();
+        loop {
+            std::thread::sleep(tick);
+            let cur = WATCHDOG_PINGS.load(Ordering::Relaxed);
+            if cur != last {
+                last = cur;
+                last_change = Instant::now();
+                continue;
+            }
+            // No IOCTL since `last_change`. A live host PINGs every `timeout/3`, so this only trips once
+            // the host is truly gone; only reap when there's something to reap.
+            if last_change.elapsed() >= timeout && crate::monitor::has_monitors() {
+                let n = crate::monitor::reap_orphaned(Duration::from_secs(3));
+                if n > 0 {
+                    dbglog!(
+                        "[pf-vd] watchdog: no host IOCTL in {WATCHDOG_TIMEOUT_S}s — host gone, departed {n} monitor(s)"
+                    );
+                }
+                last_change = Instant::now(); // don't re-reap every tick
+            }
+        }
+    });
+}
 
 /// Dispatch one control IOCTL and complete the request.
 ///
 /// # Safety
 /// `request` is the framework-provided `WDFREQUEST` for an `EvtIddCxDeviceIoControl` call.
 pub unsafe fn dispatch(request: WDFREQUEST, ioctl_code: u32) {
+    // Every inbound IOCTL is host liveness (the host PINGs on a timer, plus ADD/REMOVE/GET_INFO/…) —
+    // bump the watchdog at the top so it only fires once the host has gone truly silent. See
+    // [`start_watchdog`].
+    WATCHDOG_PINGS.fetch_add(1, Ordering::Relaxed);
     match ioctl_code {
         control::IOCTL_GET_INFO => {
             let reply = control::InfoReply {
@@ -31,10 +82,7 @@ pub unsafe fn dispatch(request: WDFREQUEST, ioctl_code: u32) {
             // SAFETY: `request` is the framework WDFREQUEST.
             unsafe { write_output_complete(request, &reply) };
         }
-        control::IOCTL_PING => {
+        control::IOCTL_PING => complete(request, STATUS_SUCCESS),
-            WATCHDOG_PINGS.fetch_add(1, Ordering::Relaxed);
-            complete(request, STATUS_SUCCESS);
-        }
         // SAFETY: `request` is the framework WDFREQUEST.
         control::IOCTL_ADD => unsafe { add(request) },
         // SAFETY: `request` is the framework WDFREQUEST.
@@ -43,12 +91,34 @@ pub unsafe fn dispatch(request: WDFREQUEST, ioctl_code: u32) {
             crate::monitor::clear_all();
             complete(request, STATUS_SUCCESS);
         }
-        // SET_RENDER_ADAPTER (hybrid-GPU render pin): STEP 4 (next).
+        // SAFETY: `request` is the framework WDFREQUEST.
-        control::IOCTL_SET_RENDER_ADAPTER => complete(request, STATUS_NOT_IMPLEMENTED),
+        control::IOCTL_SET_RENDER_ADAPTER => unsafe { set_render_adapter(request) },
         _ => complete(request, STATUS_NOT_FOUND),
     }
 }
 
+/// Sanity bounds for a requested mode — generous (covers any real client) but rejects zero/absurd
+/// values that would otherwise feed the EDID/mode math unchecked.
+fn valid_mode(width: u32, height: u32, refresh_hz: u32) -> bool {
+    (1..=16384).contains(&width)
+        && (1..=16384).contains(&height)
+        && (1..=1000).contains(&refresh_hz)
+}
+
+/// `IOCTL_SET_RENDER_ADAPTER`: pin the IddCx render adapter (hybrid-GPU IDD-push).
+///
+/// # Safety
+/// `request` is the framework `WDFREQUEST`.
+unsafe fn set_render_adapter(request: WDFREQUEST) {
+    // SAFETY: `request` is the framework WDFREQUEST.
+    let Some(req) = (unsafe { read_input::<control::SetRenderAdapterRequest>(request) }) else {
+        complete(request, STATUS_INVALID_PARAMETER);
+        return;
+    };
+    let st = crate::adapter::set_render_adapter(req.luid_low, req.luid_high);
+    complete(request, st);
+}
+
 /// `IOCTL_ADD`: create a virtual monitor at the requested mode → reply with the OS target id + LUID.
 ///
 /// # Safety
@@ -59,6 +129,10 @@ unsafe fn add(request: WDFREQUEST) {
         complete(request, STATUS_INVALID_PARAMETER);
         return;
     };
+    if !valid_mode(req.width, req.height, req.refresh_hz) {
+        complete(request, STATUS_INVALID_PARAMETER);
+        return;
+    }
     let Some((target_id, luid_low, luid_high)) =
         crate::monitor::create_monitor(req.session_id, req.width, req.height, req.refresh_hz)
     else {

packaging/windows/drivers/pf-vdisplay/src/log.rs

@@ -1,16 +1,29 @@
-//! Minimal driver logger (matches the DualSense driver). DebugView can't capture the UMDF host across
+//! Minimal driver logger. `OutputDebugStringA` always (ETW/DebugView); the optional world-writable file
-//! session 0, so besides `OutputDebugStringA` we append to a world-writable file readable over SSH. Used
+//! (`C:\Users\Public\pfvd-driver.log`, readable over SSH) is now OPT-IN — debug builds, or the
-//! only for bring-up/diagnostics; cheap and best-effort (ignores all errors).
+//! `PFVD_DEBUG_LOG` env var, only — so a RELEASE build never writes it (audit §4.4: it was an
+//! info-leak/DoS surface). Best-effort; ignores all errors. Production driver-state visibility is the
+//! SharedHeader `driver_status` channel, not this file.
 
 unsafe extern "system" {
     fn OutputDebugStringA(s: *const u8);
 }
 
+/// Whether the world-writable bring-up file log is enabled (resolved once). Off in release builds unless
+/// `PFVD_DEBUG_LOG` is set.
+fn file_log_enabled() -> bool {
+    use std::sync::OnceLock;
+    static ON: OnceLock<bool> = OnceLock::new();
+    *ON.get_or_init(|| cfg!(debug_assertions) || std::env::var_os("PFVD_DEBUG_LOG").is_some())
+}
+
 pub fn log(s: &str) {
     if let Ok(c) = std::ffi::CString::new(s) {
         // SAFETY: `c` is a valid NUL-terminated string for the duration of the call.
         unsafe { OutputDebugStringA(c.as_ptr().cast()) };
     }
+    if !file_log_enabled() {
+        return;
+    }
     use std::io::Write;
     if let Ok(mut f) = std::fs::OpenOptions::new()
         .create(true)

packaging/windows/drivers/pf-vdisplay/src/monitor.rs

@@ -6,7 +6,7 @@
 
 use std::sync::Mutex;
 use std::sync::atomic::{AtomicU32, Ordering};
-use std::time::Instant;
+use std::time::{Duration, Instant};
 
 use wdk_sys::iddcx;
 
@@ -64,6 +64,50 @@ pub static MONITOR_MODES: Mutex<Vec<MonitorObject>> = Mutex::new(Vec::new());
 /// Monitor id / EDID-serial counter (unique per created monitor).
 static NEXT_ID: AtomicU32 = AtomicU32::new(1);
 
+/// True if any virtual monitor currently exists — the host-gone watchdog only reaps when there's
+/// something to reap (see [`crate::control::start_watchdog`]).
+pub fn has_monitors() -> bool {
+    MONITOR_MODES.lock().map(|l| !l.is_empty()).unwrap_or(false)
+}
+
+/// Depart every monitor that has existed at least `grace` — the host-gone watchdog reap
+/// ([`crate::control::start_watchdog`]). The grace skips a just-created monitor (the host adds it, then
+/// starts pinging) so a momentarily-stale ping timer can't nuke a brand-new monitor. Returns the count
+/// departed. Same lock discipline as [`remove_monitor`]: drop each worker (which RAII-joins its thread)
+/// OUTSIDE the `MONITOR_MODES` lock, then depart.
+pub fn reap_orphaned(grace: Duration) -> usize {
+    let mut drained: Vec<(
+        Option<iddcx::IDDCX_MONITOR>,
+        Option<crate::swap_chain_processor::SwapChainProcessor>,
+    )> = {
+        let Ok(mut lock) = MONITOR_MODES.lock() else {
+            return 0;
+        };
+        let mut taken = Vec::new();
+        let mut i = 0;
+        while i < lock.len() {
+            if lock[i].created_at.elapsed() >= grace {
+                let mut m = lock.remove(i);
+                taken.push((m.object, m.swap_chain_processor.take()));
+            } else {
+                i += 1;
+            }
+        }
+        taken
+    };
+    let n = drained.len();
+    for (_, processor) in &mut drained {
+        drop(processor.take());
+    }
+    for (object, _) in drained {
+        if let Some(m) = object {
+            // SAFETY: `m` is a live IddCx monitor handle; departure tears it down.
+            unsafe { wdk_iddcx::IddCxMonitorDeparture(m) };
+        }
+    }
+    n
+}
+
 /// Fallback modes appended after the requested mode, so a topology change still has options.
 fn default_modes() -> Vec<Mode> {
     vec![
@@ -86,17 +130,21 @@ pub fn display_info(
     height: u32,
     refresh_rate: u32,
 ) -> wdk_sys::DISPLAYCONFIG_VIDEO_SIGNAL_INFO {
-    let clock_rate = refresh_rate * (height + 4) * (height + 4) + 1000;
+    // Compute in u64 then saturate the u32 rational numerators: the old u32 `refresh*(h+4)^2` overflows
+    // for a large mode (e.g. 8K@240), which panics→aborts the extern-"C" mode DDI in a debug build.
+    // Identical for every real mode; only an absurd (also now bounds-rejected) mode saturates.
+    let clock_rate: u64 = u64::from(refresh_rate) * u64::from(height + 4) * u64::from(height + 4) + 1000;
+    let clock_rate_u32 = u32::try_from(clock_rate).unwrap_or(u32::MAX);
     // SAFETY: building a C POD — the all-zero bit pattern is a valid uninitialized
     // DISPLAYCONFIG_VIDEO_SIGNAL_INFO; every meaningful field is assigned below.
     let mut si: wdk_sys::DISPLAYCONFIG_VIDEO_SIGNAL_INFO = unsafe { core::mem::zeroed() };
-    si.pixelRate = u64::from(clock_rate);
+    si.pixelRate = clock_rate;
     si.hSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
-        Numerator: clock_rate,
+        Numerator: clock_rate_u32,
         Denominator: height + 4,
     };
     si.vSyncFreq = wdk_sys::DISPLAYCONFIG_RATIONAL {
-        Numerator: clock_rate,
+        Numerator: clock_rate_u32,
         Denominator: (height + 4) * (height + 4),
     };
     si.activeSize = wdk_sys::DISPLAYCONFIG_2DREGION {