vhost: convert pre sorted vhost memory array to interval tree

Current pre-sorted memory region array has some limitations for future
device IOTLB conversion:

1) need extra work for adding and removing a single region, and it's
   expected to be slow because of sorting or memory re-allocation.
2) need extra work of removing a large range which may intersect
   several regions with different size.
3) need trick for a replacement policy like LRU

To overcome the above shortcomings, this patch convert it to interval
tree which can easily address the above issue with almost no extra
work.

The patch could be used for:

- Extend the current API and only let the userspace to send diffs of
  memory table.
- Simplify Device IOTLB implementation.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/net.c

@@ -1036,20 +1036,20 @@ static long vhost_net_reset_owner(struct vhost_net *n)
 	struct socket *tx_sock = NULL;
 	struct socket *rx_sock = NULL;
 	long err;
-	struct vhost_memory *memory;
+	struct vhost_umem *umem;
 
 	mutex_lock(&n->dev.mutex);
 	err = vhost_dev_check_owner(&n->dev);
 	if (err)
 		goto done;
-	memory = vhost_dev_reset_owner_prepare();
-	if (!memory) {
+	umem = vhost_dev_reset_owner_prepare();
+	if (!umem) {
 		err = -ENOMEM;
 		goto done;
 	}
 	vhost_net_stop(n, &tx_sock, &rx_sock);
 	vhost_net_flush(n);
-	vhost_dev_reset_owner(&n->dev, memory);
+	vhost_dev_reset_owner(&n->dev, umem);
 	vhost_net_vq_reset(n);
 done:
 	mutex_unlock(&n->dev.mutex);

drivers/vhost/vhost.h

@@ -55,6 +55,25 @@ struct vhost_log {
 	u64 len;
 };
 
+#define START(node) ((node)->start)
+#define LAST(node) ((node)->last)
+
+struct vhost_umem_node {
+	struct rb_node rb;
+	struct list_head link;
+	__u64 start;
+	__u64 last;
+	__u64 size;
+	__u64 userspace_addr;
+	__u64 flags_padding;
+	__u64 __subtree_last;
+};
+
+struct vhost_umem {
+	struct rb_root umem_tree;
+	struct list_head umem_list;
+};
+
 /* The virtqueue structure describes a queue attached to a device. */
 struct vhost_virtqueue {
 	struct vhost_dev *dev;
@@ -103,7 +122,7 @@ struct vhost_virtqueue {
 	struct iovec *indirect;
 	struct vring_used_elem *heads;
 	/* Protected by virtqueue mutex. */
-	struct vhost_memory *memory;
+	struct vhost_umem *umem;
 	void *private_data;
 	u64 acked_features;
 	/* Log write descriptors */
@@ -121,7 +140,6 @@ struct vhost_virtqueue {
 };
 
 struct vhost_dev {
-	struct vhost_memory *memory;
 	struct mm_struct *mm;
 	struct mutex mutex;
 	struct vhost_virtqueue **vqs;
@@ -130,14 +148,15 @@ struct vhost_dev {
 	struct eventfd_ctx *log_ctx;
 	struct llist_head work_list;
 	struct task_struct *worker;
+	struct vhost_umem *umem;
 };
 
 void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int nvqs);
 long vhost_dev_set_owner(struct vhost_dev *dev);
 bool vhost_dev_has_owner(struct vhost_dev *dev);
 long vhost_dev_check_owner(struct vhost_dev *);
-struct vhost_memory *vhost_dev_reset_owner_prepare(void);
-void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
+struct vhost_umem *vhost_dev_reset_owner_prepare(void);
+void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_umem *);
 void vhost_dev_cleanup(struct vhost_dev *, bool locked);
 void vhost_dev_stop(struct vhost_dev *);
 long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user *argp);