vmm: interrupts: clearly separate MsiInterruptGroup and InterruptRoute

MsiInterruptGroup doesn't need to know the internal field names of
InterruptRoute. Introduce two helper functions to eliminate references
to irq_fd. This is done similarly to the enable and disable helper
functions.

Also drop the pub keyword from InterruptRoute fields. It is not needed
anymore.

No functional change.

Signed-off-by: Wei Liu <liuwe@microsoft.com>

vmm/src/interrupt.rs

@@ -19,8 +19,8 @@ use vmm_sys_util::eventfd::EventFd;
 pub type Result<T> = std::io::Result<T>;
 
 struct InterruptRoute {
-    pub gsi: u32,
-    pub irq_fd: EventFd,
+    gsi: u32,
+    irq_fd: EventFd,
     registered: AtomicBool,
 }
 
@@ -69,6 +69,14 @@ impl InterruptRoute {
 
         Ok(())
     }
+
+    pub fn trigger(&self) -> Result<()> {
+        self.irq_fd.write(1)
+    }
+
+    pub fn notifier(&self) -> Option<&EventFd> {
+        Some(&self.irq_fd)
+    }
 }
 
 pub struct RoutingEntry<E> {
@@ -132,7 +140,7 @@ where
 
     fn trigger(&self, index: InterruptIndex) -> Result<()> {
         if let Some(route) = self.irq_routes.get(&index) {
-            return route.irq_fd.write(1);
+            return route.trigger();
         }
 
         Err(io::Error::new(
@@ -143,7 +151,7 @@ where
 
     fn notifier(&self, index: InterruptIndex) -> Option<&EventFd> {
         if let Some(route) = self.irq_routes.get(&index) {
-            return Some(&route.irq_fd);
+            return route.notifier();
         }
 
         None