devices: convert virtio features to a u64

The virtio specification only defines feature bits in the 0-63 range
currently, so we can represent the features as a u64.  The Linux kernel
makes the same simplifying assumption, and very few features have been
defined beyond the first 32 bits, so this is probably safe for a while.

This allows the device models to be simplified, since they no longer
need to deal with the features paging mechanism (it is handled by the
generic virtio transport code).

BUG=None
TEST=build_test; boot termina on kevin

Change-Id: I6fd86907b2bdf494466c205e85072ebfeb7f5b73
Signed-off-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1313012
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>

1 files changed, 5 insertions, 11 deletions

diff --git a/devices/src/virtio/balloon.rs b/devices/src/virtio/balloon.rs
index cc6a7e6..ffb7aab 100644
--- a/devices/src/virtio/balloon.rs
+++ b/devices/src/virtio/balloon.rs
@@ -220,7 +220,7 @@ impl Worker {
 pub struct Balloon {
     command_socket: Option<UnixDatagram>,
     config: Arc<BalloonConfig>,
-    features: u32,
+    features: u64,
     kill_evt: Option<EventFd>,
 }
 
@@ -295,18 +295,12 @@ impl VirtioDevice for Balloon {
             .store(new_actual as usize, Ordering::Relaxed);
     }
 
-    fn features(&self, page: u32) -> u32 {
-        match page {
-            0 => 1 << VIRTIO_BALLOON_F_MUST_TELL_HOST | 1 << VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
-            _ => 0u32,
-        }
+    fn features(&self) -> u64 {
+        1 << VIRTIO_BALLOON_F_MUST_TELL_HOST | 1 << VIRTIO_BALLOON_F_DEFLATE_ON_OOM
     }
 
-    fn ack_features(&mut self, page: u32, value: u32) {
-        match page {
-            0 => self.features = self.features & value,
-            _ => (),
-        };
+    fn ack_features(&mut self, value: u64) {
+        self.features = self.features & value;
     }
 
     fn activate(