[S390] guest page hinting light

Use the existing arch_alloc_page/arch_free_page callbacks to do
the guest page state transitions between stable and unused.

Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 29a7940..1d03508 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -430,6 +430,13 @@
 	  Select this option to enable the special message interface to
 	  the cooperative memory management.
 
+config PAGE_STATES
+	bool "Unused page notification"
+	help
+	  This enables the notification of unused pages to the
+	  hypervisor. The ESSA instruction is used to do the states
+	  changes between a page that has content and the unused state.
+
 config VIRT_TIMER
 	bool "Virtual CPU timer support"
 	help