xen: move FLASK entry under XSM in Kconfig

Since enabling XSM is required to enable FLASK, place the option for
FLASK below the one for XSM.  In addition, since it does not make sense
to enable XSM without any XSM providers, and FLASK is the only XSM
provider, hide the option to disable FLASK under EXPERT.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

xen/common/Kconfig

@@ -11,24 +11,6 @@ config COMPAT
 config CORE_PARKING
 	bool
 
-config FLASK
-	bool "FLux Advanced Security Kernel support"
-	default y
-	depends on XSM
-	---help---
-	  Enables the FLASK (FLux Advanced Security Kernel) support which
-	  provides a mandatory access control framework by which security
-	  enforcement, isolation, and auditing can be achieved with fine
-	  granular control via a security policy.
-
-	  If unsure, say N.
-
-config FLASK_AVC_STATS
-	def_bool y
-	depends on FLASK
-	---help---
-	  Maintain statistics on the access vector cache
-
 # Select HAS_DEVICE_TREE if device tree is supported
 config HAS_DEVICE_TREE
 	bool
@@ -137,6 +119,25 @@ config XSM
 
 	  If unsure, say N.
 
+config FLASK
+	def_bool y
+	prompt "FLux Advanced Security Kernel support" if EXPERT = "y"
+	depends on XSM
+	---help---
+	  Enables FLASK (FLux Advanced Security Kernel) as the access control
+	  mechanism used by the XSM framework.  This provides a mandatory access
+	  control framework by which security enforcement, isolation, and
+	  auditing can be achieved with fine granular control via a security
+	  policy.
+
+	  If unsure, say Y.
+
+config FLASK_AVC_STATS
+	def_bool y
+	depends on FLASK
+	---help---
+	  Maintain statistics on the access vector cache
+
 # Enable schedulers
 menu "Schedulers"
 	visible if EXPERT = "y"