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, 22 deletions

diff --git a/devices/src/virtio/p9.rs b/devices/src/virtio/p9.rs
index 2237b0d..1984096 100644
--- a/devices/src/virtio/p9.rs
+++ b/devices/src/virtio/p9.rs
@@ -357,34 +357,17 @@ impl VirtioDevice for P9 {
         QUEUE_SIZES
     }
 
-    fn features(&self, page: u32) -> u32 {
-        match page {
-            0 => self.avail_features as u32,
-            1 => (self.avail_features >> 32) as u32,
-            _ => {
-                warn!("virtio_9p got request for features page: {}", page);
-                0u32
-            }
-        }
+    fn features(&self) -> u64 {
+        self.avail_features
     }
 
-    fn ack_features(&mut self, page: u32, value: u32) {
-        let mut v = match page {
-            0 => value as u64,
-            1 => (value as u64) << 32,
-            _ => {
-                warn!("virtio_9p device cannot ack unknown feature page: {}", page);
-                0u64
-            }
-        };
+    fn ack_features(&mut self, value: u64) {
+        let mut v = value;
 
         // Check if the guest is ACK'ing a feature that we didn't claim to have.
         let unrequested_features = v & !self.avail_features;
         if unrequested_features != 0 {
-            warn!(
-                "virtio_9p got unknown feature ack: {:x}, page = {}, value = {:x}",
-                v, page, value
-            );
+            warn!("virtio_9p got unknown feature ack: {:x}", v);
 
             // Don't count these features as acked.
             v &= !unrequested_features;