[RFC 4/8] virtio-mmio: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA

[Jonah Palmer <jonah.palmer@oracle.com>]

Prevent ioeventfd from being enabled/disabled when a virtio-mmio device
has negotiated the VIRTIO_F_NOTIFICATION_DATA transport feature.

Due to ioeventfd not being able to carry the extra data associated with
this feature, the ioeventfd should be left in a disabled state for
emulated virtio-mmio devices using this feature.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
---
 hw/virtio/virtio-mmio.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 2bac77460e..fc780a03b2 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -424,7 +424,8 @@ static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
         virtio_update_irq(vdev);
         break;
     case VIRTIO_MMIO_STATUS:
-        if (!(value & VIRTIO_CONFIG_S_DRIVER_OK)) {
+        if (!(value & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            !virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
             virtio_mmio_stop_ioeventfd(proxy);
         }
 
@@ -436,7 +437,8 @@ static void virtio_mmio_write(void *opaque, hwaddr offset, uint64_t value,
 
         virtio_set_status(vdev, value & 0xff);
 
-        if (value & VIRTIO_CONFIG_S_DRIVER_OK) {
+        if ((value & VIRTIO_CONFIG_S_DRIVER_OK) &&
+            !virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
             virtio_mmio_start_ioeventfd(proxy);
         }
 
-- 
2.39.3