fix(aarch64): make WHP backend operational

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: cshung <3410332+cshung@users.noreply.github.com>

Author: cshung

src/hyperlight_host/src/hypervisor/hyperlight_vm/aarch64.rs

@@ -236,7 +236,7 @@ impl HyperlightVm {
             self.vm_can_reset_vcpu,
             "No fallback path for vcpu reset on aarch64"
         );
-        self.vm.reset_vcpu()?;
+        self.interrupt_handle.reset_vcpu(self.vm.as_mut())?;
         self.apply_sregs(cr3, sregs)?;
         Ok(())
     }

src/hyperlight_host/src/hypervisor/mod.rs

@@ -46,6 +46,8 @@ use std::sync::atomic::{AtomicU8, Ordering};
 #[cfg(any(kvm, mshv3))]
 use std::time::Duration;
 
+use self::virtual_machine::{ResetVcpuError, VirtualMachine};
+
 /// A trait for platform-specific interrupt handle implementation details
 pub(crate) trait InterruptHandleImpl: InterruptHandle {
     /// Set the thread ID for the vcpu thread
@@ -67,6 +69,11 @@ pub(crate) trait InterruptHandleImpl: InterruptHandle {
     /// Clear the cancellation request flag
     fn clear_cancel(&self);
 
+    /// Reset the vCPU while honoring platform lifecycle synchronization.
+    fn reset_vcpu(&self, vm: &mut dyn VirtualMachine) -> Result<(), ResetVcpuError> {
+        vm.reset_vcpu()
+    }
+
     /// Check if debug interrupt was requested (always returns false when gdb feature is disabled)
     fn is_debug_interrupted(&self) -> bool;
 
@@ -347,6 +354,19 @@ impl InterruptHandleImpl for WindowsInterruptHandle {
         self.state.fetch_and(!Self::RUNNING_BIT, Ordering::Release);
     }
 
+    fn reset_vcpu(&self, vm: &mut dyn VirtualMachine) -> Result<(), ResetVcpuError> {
+        let guard = self
+            .partition_state
+            .write()
+            .map_err(|e| ResetVcpuError::Unknown(e.to_string()))?;
+        if guard.dropped {
+            return Err(ResetVcpuError::Unknown(
+                "cannot reset a dropped partition".to_string(),
+            ));
+        }
+        vm.reset_vcpu()
+    }
+
     fn is_debug_interrupted(&self) -> bool {
         #[cfg(gdb)]
         {

src/hyperlight_host/src/hypervisor/regs.rs

@@ -21,13 +21,13 @@ pub(crate) use x86_64::*;
 
 #[cfg(target_arch = "aarch64")]
 mod aarch64;
-#[cfg(target_os = "windows")]
+#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
 use std::collections::HashSet;
 
 #[cfg(target_arch = "aarch64")]
 pub(crate) use aarch64::*;
 
-#[cfg(target_os = "windows")]
+#[cfg(all(target_arch = "x86_64", target_os = "windows"))]
 #[derive(Debug, PartialEq)]
 pub(crate) enum FromWhpRegisterError {
     MissingRegister(HashSet<i32>),