Changeset 82176 in vbox for trunk/src

Timestamp:

Nov 25, 2019 1:41:20 PM (5 years ago)

Author:

vboxsync

Message:

PC/BIOS: The index of the avail queue is supposed to be free running and only clipped to the queue size internally, bugref:9440

File:

• trunk/src/VBox/Devices/PC/BIOS/virtio.c (modified) (2 diffs)

trunk/src/VBox/Devices/PC/BIOS/virtio.c

@@ -467 +467 @@
 
     /* Put it into the queue. */
-    virtio->Queue.AvailRing.au16Ring[virtio->Queue.AvailRing.idxNextFree] = 0;
+    virtio->Queue.AvailRing.au16Ring[virtio->Queue.AvailRing.idxNextFree % VIRTIO_SCSI_RING_ELEM] = 0;
     virtio->Queue.AvailRing.idxNextFree++;
-    virtio->Queue.AvailRing.idxNextFree %= VIRTIO_SCSI_RING_ELEM;
 
     /* Notify the device about the new command. */
@@ -523 +522 @@
     virtio->Queue.aDescTbl[2].idxNext       = 0;
 
-    /* Put it into the queue. */
-    virtio->Queue.AvailRing.au16Ring[virtio->Queue.AvailRing.idxNextFree] = 0;
+    /* Put it into the queue, the index is supposed to be free-running and clipped to the ring size
+     * internally. The free running index is what the driver sees. */
+    virtio->Queue.AvailRing.au16Ring[virtio->Queue.AvailRing.idxNextFree % VIRTIO_SCSI_RING_ELEM] = 0;
     virtio->Queue.AvailRing.idxNextFree++;
-    virtio->Queue.AvailRing.idxNextFree %= VIRTIO_SCSI_RING_ELEM;
 
     /* Notify the device about the new command. */