vringh: IOTLB support

This patch implements the third memory accessor for vringh besides
current kernel and userspace accessors. This idea is to allow vringh
to do the address translation through an IOTLB which is implemented
via vhost_map interval tree. Users should setup and IOVA to PA mapping
in this IOTLB.

This allows us to:

- Use vringh to access virtqueues with vIOMMU
- Use vringh to implement software virtqueues for vDPA devices

Signed-off-by: Jason Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Michael S. Tsirkin <[email protected]>

Author: jasowang

drivers/vhost/Kconfig

@@ -6,6 +6,7 @@ config VHOST_IOTLB
 
 config VHOST_RING
 	tristate
+	select VHOST_IOTLB
 	help
 	  This option is selected by any driver which needs to access
 	  the host side of a virtio ring.