Virtio: Add blk VIRTIO_RING_F_EVENT_IDX feature

Previous interrupt suppress patch only supply crude interrupt suppress,
VIRTIO_RING_F_EVENT_IDX feature supply a more performant alternative:
1) where the driver specifies how far the device can progress before a
notification is required
2) where the device specifies how far the driver can progress before a
interrrupt is required.

This patch add this feature into blk.
For gpu and network, this could be added also, but gpu and network
performance don't get better.

BUG=None
TEST=run benchmark for blk in guest

Change-Id: I73fe3f8b72a9e88fd6073890bc6ab2bee891d51d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2008341
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Xiong  Zhang <xiong.y.zhang@intel.corp-partner.google.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/devices/src/virtio/block.rs b/devices/src/virtio/block.rs
index 094586f..c9dda55 100644
--- a/devices/src/virtio/block.rs
+++ b/devices/src/virtio/block.rs
@@ -20,6 +20,7 @@ use sync::Mutex;
 use sys_util::Error as SysError;
 use sys_util::Result as SysResult;
 use sys_util::{error, info, iov_max, warn, EventFd, GuestMemory, PollContext, PollToken, TimerFd};
+use virtio_sys::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
 use vm_control::{DiskControlCommand, DiskControlResponseSocket, DiskControlResult};
 
 use super::{
@@ -510,6 +511,7 @@ impl Block {
         }
 
         let mut avail_features: u64 = 1 << VIRTIO_BLK_F_FLUSH;
+        avail_features |= 1 << VIRTIO_RING_F_EVENT_IDX;
         if read_only {
             avail_features |= 1 << VIRTIO_BLK_F_RO;
         } else {
@@ -871,8 +873,8 @@ mod tests {
             let b = Block::new(Box::new(f), false, true, 512, None).unwrap();
             // writable device should set VIRTIO_BLK_F_FLUSH + VIRTIO_BLK_F_DISCARD
             // + VIRTIO_BLK_F_WRITE_ZEROES + VIRTIO_F_VERSION_1 + VIRTIO_BLK_F_BLK_SIZE
-            // + VIRTIO_BLK_F_SEG_MAX
-            assert_eq!(0x100006244, b.features());
+            // + VIRTIO_BLK_F_SEG_MAX + VIRTIO_RING_F_EVENT_IDX
+            assert_eq!(0x120006244, b.features());
         }
 
         // read-write block device, non-sparse
@@ -881,8 +883,8 @@ mod tests {
             let b = Block::new(Box::new(f), false, false, 512, None).unwrap();
             // writable device should set VIRTIO_BLK_F_FLUSH
             // + VIRTIO_BLK_F_WRITE_ZEROES + VIRTIO_F_VERSION_1 + VIRTIO_BLK_F_BLK_SIZE
-            // + VIRTIO_BLK_F_SEG_MAX
-            assert_eq!(0x100004244, b.features());
+            // + VIRTIO_BLK_F_SEG_MAX + VIRTIO_RING_F_EVENT_IDX
+            assert_eq!(0x120004244, b.features());
         }
 
         // read-only block device
@@ -891,7 +893,8 @@ mod tests {
             let b = Block::new(Box::new(f), true, true, 512, None).unwrap();
             // read-only device should set VIRTIO_BLK_F_FLUSH and VIRTIO_BLK_F_RO
             // + VIRTIO_F_VERSION_1 + VIRTIO_BLK_F_BLK_SIZE + VIRTIO_BLK_F_SEG_MAX
-            assert_eq!(0x100000264, b.features());
+            // + VIRTIO_RING_F_EVENT_IDX
+            assert_eq!(0x120000264, b.features());
         }
     }