[PATCH] vhost: Don't set vring call if guest notifier is disabled

[oenhan]

From: Huaitong Han <hanht2@chinatelecom.cn>

The vring call fd is set even when the guest does not use MSIX (e.g., virtio
PMD). This results in unnecessary CPU overhead for handling virtio interrupts.
The previous patch only optimized the condition when query_queue_notifier was
enabled and the vector was unset. However, if query_queue_notifier is disabled,
the vring call FD should also be unset to avoid this inefficiency.

Reported-by: Zhiyuan Yuan <yuanzhiyuan@chinatelecom.cn>
Signed-off-by: Huaitong Han <hanht2@chinatelecom.cn>
---
 hw/virtio/vhost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 6aa72fd434..d17e7cc6fe 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1342,8 +1342,8 @@ int vhost_virtqueue_start(struct vhost_dev *dev,
     }
 
     if (k->query_guest_notifiers &&
-        k->query_guest_notifiers(qbus->parent) &&
-        virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) {
+        (!k->query_guest_notifiers(qbus->parent) ||
+            virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR)) {
         file.fd = -1;
         r = dev->vhost_ops->vhost_set_vring_call(dev, &file);
         if (r) {
-- 
2.43.5