Revert "devices: virtio: disable MSI-X for block and net"

Re-enable MSI-X for virtio-blk and virtio-net now that the underlying
issue causing hangs at startup has been fixed (CL:1917495).

BUG=chromium:1019986
TEST=Boot Termina on nami

This reverts commit 85858f580e.

Change-Id: I5a5e197243a16aee2b2aaf3145a1180749b097b2
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1918261
Reviewed-by: Zide Chen <zide.chen@intel.com>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>

devices/src/virtio/block.rs

@@ -29,6 +29,7 @@ use super::{
 
 const QUEUE_SIZE: u16 = 256;
 const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE];
+const NUM_MSIX_VECTORS: u16 = 2;
 const SECTOR_SHIFT: u8 = 9;
 const SECTOR_SIZE: u64 = 0x01 << SECTOR_SHIFT;
 const MAX_DISCARD_SECTORS: u32 = u32::MAX;
@@ -706,6 +707,10 @@ impl VirtioDevice for Block {
         TYPE_BLOCK
     }
 
+    fn msix_vectors(&self) -> u16 {
+        NUM_MSIX_VECTORS
+    }
+
     fn queue_max_sizes(&self) -> &[u16] {
         QUEUE_SIZES
     }

devices/src/virtio/net.rs

@@ -25,6 +25,7 @@ use super::{Interrupt, Queue, Reader, VirtioDevice, Writer, TYPE_NET};
 const QUEUE_SIZE: u16 = 256;
 const NUM_QUEUES: usize = 2;
 const QUEUE_SIZES: &[u16] = &[QUEUE_SIZE, QUEUE_SIZE];
+const NUM_MSIX_VECTORS: u16 = NUM_QUEUES as u16;
 
 #[derive(Debug)]
 pub enum NetError {
@@ -406,6 +407,10 @@ where
         TYPE_NET
     }
 
+    fn msix_vectors(&self) -> u16 {
+        NUM_MSIX_VECTORS
+    }
+
     fn queue_max_sizes(&self) -> &[u16] {
         QUEUE_SIZES
     }

devices/src/virtio/vhost/net.rs

@@ -150,6 +150,10 @@ where
         TYPE_NET
     }
 
+    fn msix_vectors(&self) -> u16 {
+        NUM_MSIX_VECTORS
+    }
+
     fn queue_max_sizes(&self) -> &[u16] {
         QUEUE_SIZES
     }

devices/src/virtio/vhost/vsock.rs

@@ -112,6 +112,10 @@ impl VirtioDevice for Vsock {
         TYPE_VSOCK
     }
 
+    fn msix_vectors(&self) -> u16 {
+        NUM_MSIX_VECTORS
+    }
+
     fn queue_max_sizes(&self) -> &[u16] {
         QUEUE_SIZES
     }