[Qemu-devel] [PATCH v3 3/8] virtio: Add support for guest setting of queue size

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

The MMIO virtio transport spec allows the guest to tell the host how
large the queue size is. Add virtio_queue_set_num() function which
implements this in the QEMU common virtio support code.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 hw/virtio/virtio.c         |    8 ++++++++
 include/hw/virtio/virtio.h |    1 +
 2 files changed, 9 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 8176c14..01b05f3 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -667,6 +667,14 @@ hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
     return vdev->vq[n].pa;
 }
 
+void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
+{
+    if (num <= VIRTQUEUE_MAX_SIZE) {
+        vdev->vq[n].vring.num = num;
+        virtqueue_init(&vdev->vq[n]);
+    }
+}
+
 int virtio_queue_get_num(VirtIODevice *vdev, int n)
 {
     return vdev->vq[n].vring.num;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index a6c5c53..95c4772 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -198,6 +198,7 @@ void virtio_config_writew(VirtIODevice *vdev, uint32_t addr, uint32_t data);
 void virtio_config_writel(VirtIODevice *vdev, uint32_t addr, uint32_t data);
 void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr);
 hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n);
+void virtio_queue_set_num(VirtIODevice *vdev, int n, int num);
 int virtio_queue_get_num(VirtIODevice *vdev, int n);
 void virtio_queue_notify(VirtIODevice *vdev, int n);
 uint16_t virtio_queue_vector(VirtIODevice *vdev, int n);
-- 
1.7.9.5