virtio: Add improved queue allocation API

This leaves vring_new_virtqueue alone for compatbility, but it
adds two new improved APIs:

vring_create_virtqueue: Creates a virtqueue backed by automatically
allocated coherent memory.  (Some day it this could be extended to
support non-coherent memory, too, if there ends up being a platform
on which it's worthwhile.)

__vring_new_virtqueue: Creates a virtqueue with a manually-specified
layout.  This should allow mic_virtio to work much more cleanly.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index a156e2b6ccfe..e8d36938f09a 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -59,6 +59,35 @@ static inline void virtio_store_mb(bool weak_barriers,
 struct virtio_device;
 struct virtqueue;
 
+/*
+ * Creates a virtqueue and allocates the descriptor ring.  If
+ * may_reduce_num is set, then this may allocate a smaller ring than
+ * expected.  The caller should query virtqueue_get_ring_size to learn
+ * the actual size of the ring.
+ */
+struct virtqueue *vring_create_virtqueue(unsigned int index,
+                                         unsigned int num,
+                                         unsigned int vring_align,
+                                         struct virtio_device *vdev,
+                                         bool weak_barriers,
+                                         bool may_reduce_num,
+                                         bool (*notify)(struct virtqueue *vq),
+                                         void (*callback)(struct virtqueue *vq),
+                                         const char *name);
+
+/* Creates a virtqueue with a custom layout. */
+struct virtqueue *__vring_new_virtqueue(unsigned int index,
+                                        struct vring vring,
+                                        struct virtio_device *vdev,
+                                        bool weak_barriers,
+                                        bool (*notify)(struct virtqueue *),
+                                        void (*callback)(struct virtqueue *),
+                                        const char *name);
+
+/*
+ * Creates a virtqueue with a standard layout but a caller-allocated
+ * ring.
+ */
 struct virtqueue *vring_new_virtqueue(unsigned int index,
                                       unsigned int num,
                                       unsigned int vring_align,
@@ -68,7 +97,13 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
                                       bool (*notify)(struct virtqueue *vq),
                                       void (*callback)(struct virtqueue *vq),
                                       const char *name);
+
+/*
+ * Destroys a virtqueue.  If created with vring_create_virtqueue, this
+ * also frees the ring.
+ */
 void vring_del_virtqueue(struct virtqueue *vq);
+
 /* Filter out transport-specific feature bits. */
 void vring_transport_features(struct virtio_device *vdev);