virtio-devices: Enforce a minimum number of queues

Even though the driver can provide fewer queues than those advertised
for some device types their is a minimum number that is required for
operation.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

virtio-devices/src/balloon.rs

@@ -332,6 +332,7 @@ impl Balloon {
                 avail_features,
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 queue_sizes: QUEUE_SIZES.to_vec(),
+                min_queues: NUM_QUEUES as u16,
                 ..Default::default()
             },
             id,

virtio-devices/src/block.rs

@@ -337,6 +337,7 @@ impl<T: DiskFile> Block<T> {
                 avail_features,
                 paused_sync: Some(Arc::new(Barrier::new(num_queues + 1))),
                 queue_sizes: vec![queue_size; num_queues],
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/block_io_uring.rs

@@ -378,6 +378,7 @@ impl BlockIoUring {
                 avail_features,
                 paused_sync: Some(Arc::new(Barrier::new(num_queues + 1))),
                 queue_sizes: vec![queue_size; num_queues],
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/console.rs

@@ -348,6 +348,7 @@ impl Console {
                     queue_sizes: QUEUE_SIZES.to_vec(),
                     avail_features,
                     paused_sync: Some(Arc::new(Barrier::new(2))),
+                    min_queues: NUM_QUEUES as u16,
                     ..Default::default()
                 },
                 id,

virtio-devices/src/device.rs

@@ -224,6 +224,7 @@ pub struct VirtioCommon {
     pub epoll_threads: Option<Vec<thread::JoinHandle<()>>>,
     pub queue_sizes: Vec<u16>,
     pub device_type: u32,
+    pub min_queues: u16,
 }
 
 impl VirtioCommon {
@@ -259,6 +260,15 @@ impl VirtioCommon {
             return Err(ActivateError::BadActivate);
         }
 
+        if queues.len() < self.min_queues.into() {
+            error!(
+                "Number of enabled queues lower tham min: {} vs {}",
+                queues.len(),
+                self.min_queues
+            );
+            return Err(ActivateError::BadActivate);
+        }
+
         let kill_evt = EventFd::new(EFD_NONBLOCK).map_err(|e| {
             error!("failed creating kill EventFd: {}", e);
             ActivateError::BadActivate

virtio-devices/src/mem.rs

@@ -764,6 +764,7 @@ impl Mem {
                 avail_features,
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 queue_sizes: QUEUE_SIZES.to_vec(),
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/net.rs

@@ -256,6 +256,7 @@ impl Net {
                 avail_features,
                 queue_sizes: vec![queue_size; queue_num],
                 paused_sync: Some(Arc::new(Barrier::new((num_queues / 2) + 1))),
+                min_queues: 2,
                 ..Default::default()
             },
             id,

virtio-devices/src/pmem.rs

@@ -304,6 +304,7 @@ impl Pmem {
                 queue_sizes: QUEUE_SIZES.to_vec(),
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 avail_features,
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/rng.rs

@@ -158,6 +158,7 @@ impl Rng {
                 queue_sizes: QUEUE_SIZES.to_vec(),
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 avail_features,
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/vhost_user/blk.rs

@@ -135,6 +135,7 @@ impl Blk {
                 avail_features,
                 acked_features,
                 paused_sync: Some(Arc::new(Barrier::new(vu_cfg.num_queues + 1))),
+                min_queues: 1,
                 ..Default::default()
             },
             id,

virtio-devices/src/vhost_user/fs.rs

@@ -352,6 +352,7 @@ impl Fs {
                 acked_features,
                 queue_sizes: vec![queue_size; num_queues],
                 paused_sync: Some(Arc::new(Barrier::new(2))),
+                min_queues: NUM_QUEUE_OFFSET as u16,
                 ..Default::default()
             },
             id,

virtio-devices/src/vhost_user/net.rs

@@ -144,6 +144,7 @@ impl Net {
                 avail_features,
                 acked_features,
                 paused_sync: Some(Arc::new(Barrier::new((vu_cfg.num_queues / 2) + 1))),
+                min_queues: 2,
                 ..Default::default()
             },
             vhost_user_net,

virtio-devices/src/vsock/device.rs

@@ -337,6 +337,7 @@ where
                 avail_features,
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 queue_sizes: QUEUE_SIZES.to_vec(),
+                min_queues: NUM_QUEUES as u16,
                 ..Default::default()
             },
             id,

virtio-devices/src/watchdog.rs

@@ -193,6 +193,7 @@ impl Watchdog {
                 queue_sizes: QUEUE_SIZES.to_vec(),
                 paused_sync: Some(Arc::new(Barrier::new(2))),
                 avail_features,
+                min_queues: 1,
                 ..Default::default()
             },
             id,