[PATCH] qemu:virtio: Allow guest to defer VIRTIO_F_NOTIFY_ON_EMPTY

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



There may be cases where the guest does not want the avail queue
interrupt, even when it's empty.  For the virtio-net case, the
guest may use a different buffering scheme or decide polling for
used buffers is more efficient.  This can be accomplished by simply
checking for whether the guest has acknowledged the existing notify
on empty flag.

Signed-off-by: Alex Williamson <alex.williamson@xxxxxx>
---

 hw/virtio.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/virtio.c b/hw/virtio.c
index b94ab0f..08ea16d 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -726,9 +726,10 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
 
 void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
 {
-    /* Always notify when queue is empty */
-    if ((vq->inuse || vring_avail_idx(vq) != vq->last_avail_idx) &&
-        (vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT))
+    /* Always notify when queue is empty (when feature acknowledge) */
+    if ((vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT) &&
+        (!(vdev->features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) ||
+         (vq->inuse || vring_avail_idx(vq) != vq->last_avail_idx)))
         return;
 
     vdev->isr |= 0x01;

--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux