[PATCH v3] xenbus: advertize control feature flags

From: Paul Durrant
Date: Mon Oct 10 2016 - 06:33:32 EST


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

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
---

v2:
- Fix flag logic inversion
- Use kasprintf()

v3:
- Re-instate check for flag mistakenly removed in v2
---
drivers/xen/manage.c | 41 +++++++++++++++++++++++++++++++----------
1 file changed, 31 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index e12bd36..e16ba9f 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -170,6 +170,7 @@ out:
struct shutdown_handler {
const char *command;
void (*cb)(void);
+ bool flag;
};

static int poweroff_nb(struct notifier_block *cb, unsigned long code, void *unused)
@@ -206,21 +207,22 @@ static void do_reboot(void)
ctrl_alt_del();
}

+static struct shutdown_handler shutdown_handlers[] = {
+ { "poweroff", do_poweroff, true },
+ { "halt", do_poweroff, false },
+ { "reboot", do_reboot, true },
+#ifdef CONFIG_HIBERNATE_CALLBACKS
+ { "suspend", do_suspend, true },
+#endif
+ {NULL, NULL, false },
+};
+
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;

if (shutting_down != SHUTDOWN_INVALID)
@@ -238,7 +240,7 @@ static void shutdown_handler(struct xenbus_watch *watch,
return;
}

- for (handler = &handlers[0]; handler->command; handler++) {
+ for (handler = &shutdown_handlers[0]; handler->command; handler++) {
if (strcmp(str, handler->command) == 0)
break;
}
@@ -309,8 +311,27 @@ static struct notifier_block xen_reboot_nb = {

static int setup_shutdown_watcher(void)
{
+ static struct shutdown_handler *handler;
int err;

+ for (handler = &shutdown_handlers[0]; handler->command; handler++) {
+ char *node;
+
+ if (!handler->flag)
+ continue;
+
+ node = kasprintf(GFP_KERNEL, "feature-%s",
+ handler->command);
+ if (!node) {
+ pr_err("Failed to allocate feature flag\n");
+ return -ENOMEM;
+ }
+
+ xenbus_printf(XBT_NIL, "control", node, "%u", 1);
+
+ kfree(node);
+ }
+
err = register_xenbus_watch(&shutdown_watch);
if (err) {
pr_err("Failed to set shutdown watcher\n");
--
2.1.4