diff --git a/src/arch/x86_shared/interrupt/mod.rs b/src/arch/x86_shared/interrupt/mod.rs
index 794d5354b6..ad1ba0367f 100644
--- a/src/arch/x86_shared/interrupt/mod.rs
+++ b/src/arch/x86_shared/interrupt/mod.rs
@@ -107,6 +107,19 @@ pub unsafe fn mwait_loop(eax_hint: u32, ecx_hint: u32) {
     );
     #[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
     let _ = (eax_hint, ecx_hint);
+
+    // MWAIT returns when an interrupt fires (ecx=0 means
+    // "break on any interrupt"). The interrupt dispatcher
+    // has already run and returned by the time we get here.
+    // If the CPU was in s2idle (S2IDLE_REQUESTED was set by
+    // the kstop handler), we now know an SCI or other wake
+    // event has occurred. Clear the s2idle flag and trigger
+    // the kstop handle's EVENT_READ so acpid's main loop
+    // wakes up and runs the _WAK AML sequence.
+    if crate::scheme::acpi::s2idle_requested() {
+        crate::scheme::acpi::s2idle_request_clear();
+        crate::scheme::acpi::s2idle_signal_wake();
+    }
 }
 
 /// Probe MWAIT support and enter the deepest available C-state
diff --git a/src/scheme/acpi.rs b/src/scheme/acpi.rs
index 4ca307e818..66cede11eb 100644
--- a/src/scheme/acpi.rs
+++ b/src/scheme/acpi.rs
@@ -73,6 +73,28 @@ pub fn s2idle_requested() -> bool {
     S2IDLE_REQUESTED.load(Ordering::Acquire)
 }
 
+/// Phase I: signal acpid that s2idle MWAIT was broken by an
+/// interrupt. Called from `mwait_loop` after MWAIT returns.
+/// Triggers the kstop handle's EVENT_READ so acpid's main loop
+/// wakes and runs the \_SST(2) → \_WAK(0) → \_SST(1) AML
+/// sequence on resume.
+///
+/// Mirrors Linux 7.1 `acpi_s2idle_wake` in
+/// `drivers/acpi/sleep.c:758` — the kernel clears
+/// s2idle_state and signals the userspace ACPI driver.
+pub fn s2idle_signal_wake() {
+    let mut token = CleanLockToken::new();
+    *KSTOP_FLAG.lock(token.token()) = true;
+    if EXISTS_KSTOP_HANDLE.load(Ordering::Relaxed) {
+        crate::event::trigger(
+            GlobalSchemes::Acpi.scheme_id(),
+            HandleBits::KSTOP_HANDLE.bits(),
+            EventFlags::EVENT_READ,
+            &mut token,
+        );
+    }
+}
+
 pub fn register_kstop(token: &mut CleanLockToken) -> bool {
     *KSTOP_FLAG.lock(token.token()) = true;