vmm: Fully implement LegacyUserspaceInterruptGroup

Relying on the previous commits, the legacy interrupt implementation can
be completed. The IOAPIC handler is used to deliver the interrupt that
will be triggered through the trigger() method.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/interrupt.rs

@@ -242,17 +242,29 @@ impl InterruptSourceGroup for MsiInterruptGroup {
     }
 }
 
-pub struct LegacyUserspaceInterruptGroup {}
+pub struct LegacyUserspaceInterruptGroup {
+    ioapic: Arc<Mutex<ioapic::Ioapic>>,
+    irq: u32,
+}
 
 impl LegacyUserspaceInterruptGroup {
-    fn new() -> Self {
-        LegacyUserspaceInterruptGroup {}
+    fn new(ioapic: Arc<Mutex<ioapic::Ioapic>>, irq: u32) -> Self {
+        LegacyUserspaceInterruptGroup { ioapic, irq }
     }
 }
 
 impl InterruptSourceGroup for LegacyUserspaceInterruptGroup {
     fn trigger(&self, _index: InterruptIndex) -> Result<()> {
-        Ok(())
+        self.ioapic
+            .lock()
+            .unwrap()
+            .service_irq(self.irq as usize)
+            .map_err(|e| {
+                io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("failed to inject IRQ #{}: {:?}", self.irq, e),
+                )
+            })
     }
 
     fn update(&self, _index: InterruptIndex, _config: InterruptSourceConfig) -> Result<()> {
@@ -264,7 +276,7 @@ pub struct KvmInterruptManager {
     allocator: Arc<Mutex<SystemAllocator>>,
     vm_fd: Arc<VmFd>,
     gsi_msi_routes: Arc<Mutex<HashMap<u32, KvmRoutingEntry>>>,
-    _ioapic: Arc<Mutex<ioapic::Ioapic>>,
+    ioapic: Arc<Mutex<ioapic::Ioapic>>,
 }
 
 impl KvmInterruptManager {
@@ -278,7 +290,7 @@ impl KvmInterruptManager {
             allocator,
             vm_fd,
             gsi_msi_routes,
-            _ioapic: ioapic,
+            ioapic,
         }
     }
 }
@@ -291,7 +303,19 @@ impl InterruptManager for KvmInterruptManager {
         count: InterruptIndex,
     ) -> Result<Arc<Box<dyn InterruptSourceGroup>>> {
         let interrupt_source_group: Arc<Box<dyn InterruptSourceGroup>> = match interrupt_type {
-            PIN_IRQ => Arc::new(Box::new(LegacyUserspaceInterruptGroup::new())),
+            PIN_IRQ => {
+                if count > 1 {
+                    return Err(io::Error::new(
+                        io::ErrorKind::Other,
+                        "Legacy cannot support more than one interrupt",
+                    ));
+                }
+
+                Arc::new(Box::new(LegacyUserspaceInterruptGroup::new(
+                    self.ioapic.clone(),
+                    base as u32,
+                )))
+            }
             PCI_MSI_IRQ => {
                 let mut allocator = self.allocator.lock().unwrap();
                 let mut irq_routes: HashMap<InterruptIndex, InterruptRoute> =