[Qemu-devel] [PATCH 2/2] hw/virtio/virtio-mmio: Make QueueNumMax read 0 for unavailable queues

[Peter Maydell <peter.maydell@linaro.org>]

The virtio-mmio spec says that QueueNumMax must read zero for queues
which are unavailable; implement this, rather than always returning
VIRTQUEUE_MAX_SIZE.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/virtio/virtio-mmio.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 54d6679..aefb7e4 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -151,6 +151,9 @@ static uint64_t virtio_mmio_read(void *opaque, hwaddr offset, unsigned size)
         }
         return proxy->host_features;
     case VIRTIO_MMIO_QUEUENUMMAX:
+        if (virtio_queue_get_num(vdev, vdev->queue_sel) == 0) {
+            return 0;
+        }
         return VIRTQUEUE_MAX_SIZE;
     case VIRTIO_MMIO_QUEUEPFN:
         return virtio_queue_get_addr(vdev, vdev->queue_sel)
-- 
1.7.9.5