RE: [PATCH v2] xenbus: advertise control feature flags

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Juergen Gross [mailto:jgross@suse.com]
> Sent: 11 October 2016 12:34
> To: linux-kernel@vger.kernel.org; xen-devel@lists.xen.org
> Cc: David Vrabel <david.vrabel@citrix.com>; boris.ostrovsky@oracle.com;
> Paul Durrant <Paul.Durrant@citrix.com>; Juergen Gross <jgross@suse.com>
> Subject: [PATCH v2] xenbus: advertise control feature flags
> 
> 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@citrix.com>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: David Vrabel <david.vrabel@citrix.com>

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> ---
> 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