[Xen-devel] [PATCH v2] xenbus: advertise control feature flags

[Juergen Gross <jgross@xxxxxxxx>]

The Xen docs specify several flags which a guest can set to advertise
which values of the xenstore control/shutdown key it will recognize.
This patch adds code to write all the relevant feature-flag keys.

Based-on-patch-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>
---
V2: use snprintf() instead of sprintf()
---
 drivers/xen/manage.c | 45 +++++++++++++++++++++++++++++----------------
 1 file changed, 29 insertions(+), 16 deletions(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index e12bd36..26e5e85 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -168,7 +168,9 @@ static void do_suspend(void)
 #endif /* CONFIG_HIBERNATE_CALLBACKS */
 
 struct shutdown_handler {
-       const char *command;
+#define SHUTDOWN_CMD_SIZE 11
+       const char command[SHUTDOWN_CMD_SIZE];
+       bool flag;
        void (*cb)(void);
 };
 
@@ -206,22 +208,22 @@ static void do_reboot(void)
        ctrl_alt_del();
 }
 
+static struct shutdown_handler shutdown_handlers[] = {
+       { "poweroff",   true,   do_poweroff },
+       { "halt",       false,  do_poweroff },
+       { "reboot",     true,   do_reboot   },
+#ifdef CONFIG_HIBERNATE_CALLBACKS
+       { "suspend",    true,   do_suspend  },
+#endif
+};
+
 static void shutdown_handler(struct xenbus_watch *watch,
                             const char **vec, unsigned int len)
 {
        char *str;
        struct xenbus_transaction xbt;
        int err;
-       static struct shutdown_handler handlers[] = {
-               { "poweroff",   do_poweroff },
-               { "halt",       do_poweroff },
-               { "reboot",     do_reboot   },
-#ifdef CONFIG_HIBERNATE_CALLBACKS
-               { "suspend",    do_suspend  },
-#endif
-               {NULL, NULL},
-       };
-       static struct shutdown_handler *handler;
+       int idx;
 
        if (shutting_down != SHUTDOWN_INVALID)
                return;
@@ -238,13 +240,13 @@ static void shutdown_handler(struct xenbus_watch *watch,
                return;
        }
 
-       for (handler = &handlers[0]; handler->command; handler++) {
-               if (strcmp(str, handler->command) == 0)
+       for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
+               if (strcmp(str, shutdown_handlers[idx].command) == 0)
                        break;
        }
 
        /* Only acknowledge commands which we are prepared to handle. */
-       if (handler->cb)
+       if (idx < ARRAY_SIZE(shutdown_handlers))
                xenbus_write(xbt, "control", "shutdown", "");
 
        err = xenbus_transaction_end(xbt, 0);
@@ -253,8 +255,8 @@ static void shutdown_handler(struct xenbus_watch *watch,
                goto again;
        }
 
-       if (handler->cb) {
-               handler->cb();
+       if (idx < ARRAY_SIZE(shutdown_handlers)) {
+               shutdown_handlers[idx].cb();
        } else {
                pr_info("Ignoring shutdown request: %s\n", str);
                shutting_down = SHUTDOWN_INVALID;
@@ -310,6 +312,9 @@ static struct notifier_block xen_reboot_nb = {
 static int setup_shutdown_watcher(void)
 {
        int err;
+       int idx;
+#define FEATURE_PATH_SIZE (SHUTDOWN_CMD_SIZE + sizeof("feature-"))
+       char node[FEATURE_PATH_SIZE];
 
        err = register_xenbus_watch(&shutdown_watch);
        if (err) {
@@ -326,6 +331,14 @@ static int setup_shutdown_watcher(void)
        }
 #endif
 
+       for (idx = 0; idx < ARRAY_SIZE(shutdown_handlers); idx++) {
+               if (!shutdown_handlers[idx].flag)
+                       continue;
+               snprintf(node, FEATURE_PATH_SIZE, "feature-%s",
+                        shutdown_handlers[idx].command);
+               xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+       }
+
        return 0;
 }
 
-- 
2.6.6


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