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

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----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


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