stubdom: configure kexec for PVH Xenstore stubdom

Add the required configuration settings to enable kexec in the PVH
variant of xenstore-stubdom. This is required to support live update.

Set the number of kexec module pages to 18 in order to support using
the kexec module memory for the stubdom's 9pfs granted pages.

In Xenstore code test the CONFIG_KEXEC setting in order to determine
whether stubdom live update is supported (PV xenstore-stubdom doesn't
have live update support, as it lacks kexec).

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>

stubdom/xenstorepvh-minios.cfg

@@ -8,4 +8,6 @@ CONFIG_CONSFRONT=n
 CONFIG_LWIP=n
 CONFIG_9PFRONT=y
 CONFIG_BALLOON=y
+CONFIG_KEXEC=y
+CONFIG_KEXEC_MODULE_PAGES=18
 XEN_INTERFACE_VERSION=__XEN_LATEST_INTERFACE_VERSION__

tools/xenstored/core.h

@@ -45,6 +45,11 @@
 #endif
 #endif
 
+/* Live update in stubdom case needs kexec support. */
+#if defined(__MINIOS__) && !defined(CONFIG_KEXEC)
+#define NO_LIVE_UPDATE
+#endif
+
 /* DEFAULT_BUFFER_SIZE should be large enough for each errno string. */
 #define DEFAULT_BUFFER_SIZE 16