virtio/user: negotiate VHOST_USER_PROTOCOL_F_CONFIG

It was introduced a while after the original GET/SET_CONFIG
implementation in QEMU, but within the same QEMU release (2.12?).
It is required by the vhost-user spec. Rte_vhost doesn't check
it, so everything worked so far, but other implementations
might (and should) reject our GET_CONFIG requests right now.

As a part of this feature, we should also check the same
flag before sending GET/SET_CONFIG messages to respect those
devices that really don't implement F_CONFIG. This is done
in a separate patch.

Change-Id: Ib7e9b11a0074f4aee70609af0cad2ef59a8bf427
Signed-off-by: Dariusz Stojaczyk <[email protected]>
Reviewed-on: https://review.gerrithub.io/417459
Tested-by: SPDK Automated Test System <[email protected]>
Reviewed-by: Jim Harris <[email protected]>
Reviewed-by: Ben Walker <[email protected]>

lib/virtio/virtio_user.c

@@ -47,7 +47,8 @@
 #include "spdk_internal/virtio.h"
 
 #define VIRTIO_USER_SUPPORTED_PROTOCOL_FEATURES \
-	((1ULL << VHOST_USER_PROTOCOL_F_MQ))
+	((1ULL << VHOST_USER_PROTOCOL_F_MQ) | \
+	(1ULL << VHOST_USER_PROTOCOL_F_CONFIG))
 
 static int
 virtio_user_create_queue(struct virtio_dev *vdev, uint32_t queue_sel)

lib/virtio/virtio_user/vhost.h

@@ -47,6 +47,10 @@
 #define VHOST_USER_PROTOCOL_F_MQ	0
 #endif
 
+#ifndef VHOST_USER_PROTOCOL_F_CONFIG
+#define VHOST_USER_PROTOCOL_F_CONFIG	9
+#endif
+
 enum vhost_user_request {
 	VHOST_USER_NONE = 0,
 	VHOST_USER_GET_FEATURES = 1,