vhost-vdpa: support IOTLB batching hints

This patches extend the vhost IOTLB API to accept batch updating hints
form userspace. When userspace wants update the device IOTLB in a
batch, it may do:

1) Write vhost_iotlb_msg with VHOST_IOTLB_BATCH_BEGIN flag
2) Perform a batch of IOTLB updating via VHOST_IOTLB_UPDATE/INVALIDATE
3) Write vhost_iotlb_msg with VHOST_IOTLB_BATCH_END flag

Vhost-vdpa may decide to batch the IOMMU/IOTLB updating in step 3 when
vDPA device support set_map() ops. This is useful for the vDPA device
that want to know all the mappings to tweak their own DMA translation
logic.

For vDPA device that doesn't require set_map(), no behavior changes.

This capability is advertised via VHOST_BACKEND_F_IOTLB_BATCH capability.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20200804162048.22587-5-eli@mellanox.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
index 669457ce5c48..9a269a88a6ff 100644
--- a/include/uapi/linux/vhost_types.h
+++ b/include/uapi/linux/vhost_types.h
@@ -60,6 +60,17 @@ struct vhost_iotlb_msg {
 #define VHOST_IOTLB_UPDATE         2
 #define VHOST_IOTLB_INVALIDATE     3
 #define VHOST_IOTLB_ACCESS_FAIL    4
+/*
+ * VHOST_IOTLB_BATCH_BEGIN and VHOST_IOTLB_BATCH_END allow modifying
+ * multiple mappings in one go: beginning with
+ * VHOST_IOTLB_BATCH_BEGIN, followed by any number of
+ * VHOST_IOTLB_UPDATE messages, and ending with VHOST_IOTLB_BATCH_END.
+ * When one of these two values is used as the message type, the rest
+ * of the fields in the message are ignored. There's no guarantee that
+ * these changes take place automatically in the device.
+ */
+#define VHOST_IOTLB_BATCH_BEGIN    5
+#define VHOST_IOTLB_BATCH_END      6
 	__u8 type;
 };