Virtio: Add virtio block irq suppress

The flag in avail descriptor supplies irq suppress, it could reduce irq
injection from device, so many redundant interrupts could be removed
from guest, then improve guest performance.

BUG=None
TEST=run fio read and fio write in guest

Change-Id: I68789d8ca24d0e84d0b446db65057f4da2fac56f
Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2008339
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>

2 files changed, 20 insertions, 2 deletions

diff --git a/devices/src/virtio/block.rs b/devices/src/virtio/block.rs
index 65be6d5..1e9c63e 100644
--- a/devices/src/virtio/block.rs
+++ b/devices/src/virtio/block.rs
@@ -325,7 +325,7 @@ impl Worker {
             };
 
             queue.add_used(&self.mem, desc_index, len as u32);
-            self.interrupt.signal_used_queue(queue.vector);
+            queue.trigger_interrupt(&self.mem, &self.interrupt);
             queue.set_notify(&self.mem, true);
         }
     }
diff --git a/devices/src/virtio/queue.rs b/devices/src/virtio/queue.rs
index b3c738c..15dc3e1 100644
--- a/devices/src/virtio/queue.rs
+++ b/devices/src/virtio/queue.rs
@@ -8,7 +8,7 @@ use std::sync::atomic::{fence, Ordering};
 
 use sys_util::{error, GuestAddress, GuestMemory};
 
-use super::VIRTIO_MSI_NO_VECTOR;
+use super::{Interrupt, VIRTIO_MSI_NO_VECTOR};
 
 const VIRTQ_DESC_F_NEXT: u16 = 0x1;
 const VIRTQ_DESC_F_WRITE: u16 = 0x2;
@@ -16,6 +16,7 @@ const VIRTQ_DESC_F_WRITE: u16 = 0x2;
 const VIRTQ_DESC_F_INDIRECT: u16 = 0x4;
 
 const VIRTQ_USED_F_NO_NOTIFY: u16 = 0x1;
+const VIRTQ_AVAIL_F_NO_INTERRUPT: u16 = 0x1;
 
 /// An iterator over a single descriptor chain.  Not to be confused with AvailIter,
 /// which iterates over the descriptor chain heads in a queue.
@@ -395,4 +396,21 @@ impl Queue {
         }
         mem.write_obj_at_addr(used_flags, self.used_ring).unwrap();
     }
+
+    // Check Whether guest enable interrupt injection or not.
+    fn available_interrupt_enabled(&self, mem: &GuestMemory) -> bool {
+        let avail_flags: u16 = mem.read_obj_from_addr(self.avail_ring).unwrap();
+        if avail_flags & VIRTQ_AVAIL_F_NO_INTERRUPT == VIRTQ_AVAIL_F_NO_INTERRUPT {
+            false
+        } else {
+            true
+        }
+    }
+
+    /// inject interrupt into guest on this queue
+    pub fn trigger_interrupt(&self, mem: &GuestMemory, interrupt: &Interrupt) {
+        if self.available_interrupt_enabled(mem) {
+            interrupt.signal_used_queue(self.vector);
+        }
+    }
 }