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

From: Paul Durrant
Date: Tue Oct 11 2016 - 08:19:36 EST


> -----Original Message-----
> From: Juergen Gross [mailto:jgross@xxxxxxxx]
> Sent: 11 October 2016 12:34
> To: linux-kernel@xxxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx
> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>; boris.ostrovsky@xxxxxxxxxx;
> Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Juergen Gross <jgross@xxxxxxxx>
> 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@xxxxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@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