virtio-devices: Pass a list of tuples for virtqueues

Instead of passing separately a list of Queues and the equivalent list
of EventFds, we consolidate these two through a tuple along with the
queue index.

The queue index can be very useful if looking for the actual index
related to the queue, no matter if other queues have been enabled or
not.

It's also convenient to have the EventFd associated with the Queue so
that we don't have to carry two lists with the same amount of items.

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

virtio-devices/src/watchdog.rs

@@ -47,7 +47,7 @@ const WATCHDOG_TIMER_INTERVAL: i64 = 15;
 const WATCHDOG_TIMEOUT: u64 = WATCHDOG_TIMER_INTERVAL as u64 + 5;
 
 struct WatchdogEpollHandler {
-    queues: Vec<Queue<GuestMemoryAtomic<GuestMemoryMmap>>>,
+    queue: Queue<GuestMemoryAtomic<GuestMemoryMmap>>,
     interrupt_cb: Arc<dyn VirtioInterrupt>,
     queue_evt: EventFd,
     kill_evt: EventFd,
@@ -61,7 +61,7 @@ impl WatchdogEpollHandler {
     // The main queue is very simple - the driver "pings" the device by passing it a (write-only)
     // descriptor. In response the device writes a 1 into the descriptor and returns it to the driver
     fn process_queue(&mut self) -> bool {
-        let queue = &mut self.queues[0];
+        let queue = &mut self.queue;
         let mut used_desc_heads = [(0, 0); QUEUE_SIZE as usize];
         let mut used_count = 0;
         for mut desc_chain in queue.iter().unwrap() {
@@ -291,10 +291,9 @@ impl VirtioDevice for Watchdog {
         &mut self,
         _mem: GuestMemoryAtomic<GuestMemoryMmap>,
         interrupt_cb: Arc<dyn VirtioInterrupt>,
-        queues: Vec<Queue<GuestMemoryAtomic<GuestMemoryMmap>>>,
-        mut queue_evts: Vec<EventFd>,
+        mut queues: Vec<(usize, Queue<GuestMemoryAtomic<GuestMemoryMmap>>, EventFd)>,
     ) -> ActivateResult {
-        self.common.activate(&queues, &queue_evts, &interrupt_cb)?;
+        self.common.activate(&queues, &interrupt_cb)?;
         let (kill_evt, pause_evt) = self.common.dup_eventfds();
 
         let reset_evt = self.reset_evt.try_clone().map_err(|e| {
@@ -307,10 +306,12 @@ impl VirtioDevice for Watchdog {
             ActivateError::BadActivate
         })?;
 
+        let (_, queue, queue_evt) = queues.remove(0);
+
         let mut handler = WatchdogEpollHandler {
-            queues,
+            queue,
             interrupt_cb,
-            queue_evt: queue_evts.remove(0),
+            queue_evt,
             kill_evt,
             pause_evt,
             timer,