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Re: [Xen-devel] [PATCH, resend] Xen watchdog driver

To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH, resend] Xen watchdog driver
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Mon, 14 Feb 2011 09:56:02 -0500
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, linux-watchdog@xxxxxxxxxxxxxxx, Jan Beulich <JBeulich@xxxxxxxxxx>, Ian Campbell <ian.campbell@xxxxxxxxxx>
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On Thu, Jan 27, 2011 at 03:42:48PM +0000, Jan Beulich wrote:
> While the hypervisor change adding SCHEDOP_watchdog support included a
> daemon to make use of the new functionality, having a kernel driver
> for /dev/watchdog so that user space code doesn't need to distinguish
> non-Xen and Xen seems to be preferable.

Hey Andrew,
I was wondering if you could help us out. Jan posted this patch
way back in Sep, then again in Oct on the xen-watchdog mailing list
with with no responses except Ian's Ack and my Reviewed-by. Would you
be OK taking this patch under your wing or do you think I ought to
send a git pull to Linus during the 2.6.39 merge window directly?

Cheers,
Konrad
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx> (on theAXen aspects of the 
> patch)
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> 
> ---
>  drivers/watchdog/Kconfig      |   10 +
>  drivers/watchdog/Makefile     |    3 
>  drivers/watchdog/xen_wdt.c    |  359 
> ++++++++++++++++++++++++++++++++++++++++++
>  include/xen/interface/sched.h |   34 +++
>  4 files changed, 406 insertions(+)
> 
> --- 2.6.38-rc2/drivers/watchdog/Kconfig
> +++ 2.6.38-rc2-xen-watchdog/drivers/watchdog/Kconfig
> @@ -1119,6 +1119,16 @@ config WATCHDOG_RIO
>  
>  # XTENSA Architecture
>  
> +# Xen Architecture
> +
> +config XEN_WDT
> +     tristate "Xen Watchdog support"
> +     depends on XEN
> +     help
> +       Say Y here to support the hypervisor watchdog capability provided
> +       by Xen 4.0 and newer.  The watchdog timeout period is normally one
> +       minute but can be changed with a boot-time parameter.
> +
>  #
>  # ISA-based Watchdog Cards
>  #
> --- 2.6.38-rc2/drivers/watchdog/Makefile
> +++ 2.6.38-rc2-xen-watchdog/drivers/watchdog/Makefile
> @@ -148,6 +148,9 @@ obj-$(CONFIG_WATCHDOG_CP1XXX)             += cpwd.o
>  
>  # XTENSA Architecture
>  
> +# Xen
> +obj-$(CONFIG_XEN_WDT) += xen_wdt.o
> +
>  # Architecture Independant
>  obj-$(CONFIG_WM831X_WATCHDOG) += wm831x_wdt.o
>  obj-$(CONFIG_WM8350_WATCHDOG) += wm8350_wdt.o
> --- 2.6.38-rc2/drivers/watchdog/xen_wdt.c
> +++ 2.6.38-rc2-xen-watchdog/drivers/watchdog/xen_wdt.c
> @@ -0,0 +1,359 @@
> +/*
> + *   Xen Watchdog Driver
> + *
> + *   (c) Copyright 2010 Novell, Inc.
> + *
> + *   This program is free software; you can redistribute it and/or
> + *   modify it under the terms of the GNU General Public License
> + *   as published by the Free Software Foundation; either version
> + *   2 of the License, or (at your option) any later version.
> + */
> +
> +#define DRV_NAME     "wdt"
> +#define DRV_VERSION  "0.01"
> +#define PFX          DRV_NAME ": "
> +
> +#include <linux/bug.h>
> +#include <linux/errno.h>
> +#include <linux/fs.h>
> +#include <linux/hrtimer.h>
> +#include <linux/kernel.h>
> +#include <linux/ktime.h>
> +#include <linux/init.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> +#include <linux/uaccess.h>
> +#include <linux/watchdog.h>
> +#include <xen/xen.h>
> +#include <asm/xen/hypercall.h>
> +#include <xen/interface/sched.h>
> +
> +static struct platform_device *platform_device;
> +static DEFINE_SPINLOCK(wdt_lock);
> +static struct sched_watchdog wdt;
> +static __kernel_time_t wdt_expires;
> +static bool is_active, expect_release;
> +
> +#define WATCHDOG_TIMEOUT 60 /* in seconds */
> +static unsigned int timeout = WATCHDOG_TIMEOUT;
> +module_param(timeout, uint, S_IRUGO);
> +MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
> +     "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, S_IRUGO);
> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
> +     "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +static inline __kernel_time_t set_timeout(void)
> +{
> +     wdt.timeout = timeout;
> +     return ktime_to_timespec(ktime_get()).tv_sec + timeout;
> +}
> +
> +static int xen_wdt_start(void)
> +{
> +     __kernel_time_t expires;
> +     int err;
> +
> +     spin_lock(&wdt_lock);
> +
> +     expires = set_timeout();
> +     if (!wdt.id)
> +             err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
> +     else
> +             err = -EBUSY;
> +     if (err > 0) {
> +             wdt.id = err;
> +             wdt_expires = expires;
> +             err = 0;
> +     } else
> +             BUG_ON(!err);
> +
> +     spin_unlock(&wdt_lock);
> +
> +     return err;
> +}
> +
> +static int xen_wdt_stop(void)
> +{
> +     int err = 0;
> +
> +     spin_lock(&wdt_lock);
> +
> +     wdt.timeout = 0;
> +     if (wdt.id)
> +             err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
> +     if (!err)
> +             wdt.id = 0;
> +
> +     spin_unlock(&wdt_lock);
> +
> +     return err;
> +}
> +
> +static int xen_wdt_kick(void)
> +{
> +     __kernel_time_t expires;
> +     int err;
> +
> +     spin_lock(&wdt_lock);
> +
> +     expires = set_timeout();
> +     if (wdt.id)
> +             err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
> +     else
> +             err = -ENXIO;
> +     if (!err)
> +             wdt_expires = expires;
> +
> +     spin_unlock(&wdt_lock);
> +
> +     return err;
> +}
> +
> +static int xen_wdt_open(struct inode *inode, struct file *file)
> +{
> +     int err;
> +
> +     /* /dev/watchdog can only be opened once */
> +     if (xchg(&is_active, true))
> +             return -EBUSY;
> +
> +     err = xen_wdt_start();
> +     if (err == -EBUSY)
> +             err = xen_wdt_kick();
> +     return err ?: nonseekable_open(inode, file);
> +}
> +
> +static int xen_wdt_release(struct inode *inode, struct file *file)
> +{
> +     if (expect_release)
> +             xen_wdt_stop();
> +     else {
> +             printk(KERN_CRIT PFX
> +                    "unexpected close, not stopping watchdog!\n");
> +             xen_wdt_kick();
> +     }
> +     is_active = false;
> +     expect_release = false;
> +     return 0;
> +}
> +
> +static ssize_t xen_wdt_write(struct file *file, const char __user *data,
> +                          size_t len, loff_t *ppos)
> +{
> +     /* See if we got the magic character 'V' and reload the timer */
> +     if (len) {
> +             if (!nowayout) {
> +                     size_t i;
> +
> +                     /* in case it was set long ago */
> +                     expect_release = false;
> +
> +                     /* scan to see whether or not we got the magic
> +                        character */
> +                     for (i = 0; i != len; i++) {
> +                             char c;
> +                             if (get_user(c, data + i))
> +                                     return -EFAULT;
> +                             if (c == 'V')
> +                                     expect_release = true;
> +                     }
> +             }
> +
> +             /* someone wrote to us, we should reload the timer */
> +             xen_wdt_kick();
> +     }
> +     return len;
> +}
> +
> +static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
> +                       unsigned long arg)
> +{
> +     int new_options, retval = -EINVAL;
> +     int new_timeout;
> +     int __user *argp = (void __user *)arg;
> +     static const struct watchdog_info ident = {
> +             .options =              WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
> +             .firmware_version =     0,
> +             .identity =             DRV_NAME,
> +     };
> +
> +     switch (cmd) {
> +     case WDIOC_GETSUPPORT:
> +             return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
> +
> +     case WDIOC_GETSTATUS:
> +     case WDIOC_GETBOOTSTATUS:
> +             return put_user(0, argp);
> +
> +     case WDIOC_SETOPTIONS:
> +             if (get_user(new_options, argp))
> +                     return -EFAULT;
> +
> +             if (new_options & WDIOS_DISABLECARD)
> +                     retval = xen_wdt_stop();
> +             if (new_options & WDIOS_ENABLECARD) {
> +                     retval = xen_wdt_start();
> +                     if (retval == -EBUSY)
> +                             retval = xen_wdt_kick();
> +             }
> +             return retval;
> +
> +     case WDIOC_KEEPALIVE:
> +             xen_wdt_kick();
> +             return 0;
> +
> +     case WDIOC_SETTIMEOUT:
> +             if (get_user(new_timeout, argp))
> +                     return -EFAULT;
> +             if (!new_timeout)
> +                     return -EINVAL;
> +             timeout = new_timeout;
> +             xen_wdt_kick();
> +             /* fall through */
> +     case WDIOC_GETTIMEOUT:
> +             return put_user(timeout, argp);
> +
> +     case WDIOC_GETTIMELEFT:
> +             retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
> +             return put_user(retval, argp);
> +     }
> +
> +     return -ENOTTY;
> +}
> +
> +static const struct file_operations xen_wdt_fops = {
> +     .owner =                THIS_MODULE,
> +     .llseek =               no_llseek,
> +     .write =                xen_wdt_write,
> +     .unlocked_ioctl =       xen_wdt_ioctl,
> +     .open =                 xen_wdt_open,
> +     .release =              xen_wdt_release,
> +};
> +
> +static struct miscdevice xen_wdt_miscdev = {
> +     .minor =        WATCHDOG_MINOR,
> +     .name =         "watchdog",
> +     .fops =         &xen_wdt_fops,
> +};
> +
> +static int __devinit xen_wdt_probe(struct platform_device *dev)
> +{
> +     struct sched_watchdog wd = { .id = ~0 };
> +     int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
> +
> +     switch (ret) {
> +     case -EINVAL:
> +             if (!timeout) {
> +                     timeout = WATCHDOG_TIMEOUT;
> +                     printk(KERN_INFO PFX
> +                            "timeout value invalid, using %d\n", timeout);
> +             }
> +
> +             ret = misc_register(&xen_wdt_miscdev);
> +             if (ret) {
> +                     printk(KERN_ERR PFX
> +                            "cannot register miscdev on minor=%d (%d)\n",
> +                            WATCHDOG_MINOR, ret);
> +                     break;
> +             }
> +
> +             printk(KERN_INFO PFX
> +                    "initialized (timeout=%ds, nowayout=%d)\n",
> +                    timeout, nowayout);
> +             break;
> +
> +     case -ENOSYS:
> +             printk(KERN_INFO PFX "not supported\n");
> +             ret = -ENODEV;
> +             break;
> +
> +     default:
> +             printk(KERN_INFO PFX "bogus return value %d\n", ret);
> +             break;
> +     }
> +
> +     return ret;
> +}
> +
> +static int __devexit xen_wdt_remove(struct platform_device *dev)
> +{
> +     /* Stop the timer before we leave */
> +     if (!nowayout)
> +             xen_wdt_stop();
> +
> +     misc_deregister(&xen_wdt_miscdev);
> +
> +     return 0;
> +}
> +
> +static void xen_wdt_shutdown(struct platform_device *dev)
> +{
> +     xen_wdt_stop();
> +}
> +
> +static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
> +{
> +     return xen_wdt_stop();
> +}
> +
> +static int xen_wdt_resume(struct platform_device *dev)
> +{
> +     return xen_wdt_start();
> +}
> +
> +static struct platform_driver xen_wdt_driver = {
> +     .probe          = xen_wdt_probe,
> +     .remove         = __devexit_p(xen_wdt_remove),
> +     .shutdown       = xen_wdt_shutdown,
> +     .suspend        = xen_wdt_suspend,
> +     .resume         = xen_wdt_resume,
> +     .driver         = {
> +             .owner  = THIS_MODULE,
> +             .name   = DRV_NAME,
> +     },
> +};
> +
> +static int __init xen_wdt_init_module(void)
> +{
> +     int err;
> +
> +     if (!xen_domain())
> +             return -ENODEV;
> +
> +     printk(KERN_INFO PFX "Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
> +
> +     err = platform_driver_register(&xen_wdt_driver);
> +     if (err)
> +             return err;
> +
> +     platform_device = platform_device_register_simple(DRV_NAME,
> +                                                               -1, NULL, 0);
> +     if (IS_ERR(platform_device)) {
> +             err = PTR_ERR(platform_device);
> +             platform_driver_unregister(&xen_wdt_driver);
> +     }
> +
> +     return err;
> +}
> +
> +static void __exit xen_wdt_cleanup_module(void)
> +{
> +     platform_device_unregister(platform_device);
> +     platform_driver_unregister(&xen_wdt_driver);
> +     printk(KERN_INFO PFX "module unloaded\n");
> +}
> +
> +module_init(xen_wdt_init_module);
> +module_exit(xen_wdt_cleanup_module);
> +
> +MODULE_AUTHOR("Jan Beulich <jbeulich@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
> +MODULE_VERSION(DRV_VERSION);
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
> --- 2.6.38-rc2/include/xen/interface/sched.h
> +++ 2.6.38-rc2-xen-watchdog/include/xen/interface/sched.h
> @@ -65,6 +65,39 @@ struct sched_poll {
>  DEFINE_GUEST_HANDLE_STRUCT(sched_poll);
>  
>  /*
> + * Declare a shutdown for another domain. The main use of this function is
> + * in interpreting shutdown requests and reasons for fully-virtualized
> + * domains.  A para-virtualized domain may use SCHEDOP_shutdown directly.
> + * @arg == pointer to sched_remote_shutdown structure.
> + */
> +#define SCHEDOP_remote_shutdown        4
> +struct sched_remote_shutdown {
> +    domid_t domain_id;         /* Remote domain ID */
> +    unsigned int reason;       /* SHUTDOWN_xxx reason */
> +};
> +
> +/*
> + * Latch a shutdown code, so that when the domain later shuts down it
> + * reports this code to the control tools.
> + * @arg == as for SCHEDOP_shutdown.
> + */
> +#define SCHEDOP_shutdown_code 5
> +
> +/*
> + * Setup, poke and destroy a domain watchdog timer.
> + * @arg == pointer to sched_watchdog structure.
> + * With id == 0, setup a domain watchdog timer to cause domain shutdown
> + *               after timeout, returns watchdog id.
> + * With id != 0 and timeout == 0, destroy domain watchdog timer.
> + * With id != 0 and timeout != 0, poke watchdog timer and set new timeout.
> + */
> +#define SCHEDOP_watchdog    6
> +struct sched_watchdog {
> +    uint32_t id;                /* watchdog ID */
> +    uint32_t timeout;           /* timeout */
> +};
> +
> +/*
>   * Reason codes for SCHEDOP_shutdown. These may be interpreted by control
>   * software to determine the appropriate action. For the most part, Xen does
>   * not care about the shutdown code.
> @@ -73,5 +106,6 @@ DEFINE_GUEST_HANDLE_STRUCT(sched_poll);
>  #define SHUTDOWN_reboot     1  /* Clean up, kill, and then restart.          
> */
>  #define SHUTDOWN_suspend    2  /* Clean up, save suspend info, kill.         
> */
>  #define SHUTDOWN_crash      3  /* Tell controller we've crashed.             
> */
> +#define SHUTDOWN_watchdog   4  /* Restart because watchdog time expired.     
> */
>  
>  #endif /* __XEN_PUBLIC_SCHED_H__ */
> 
> 
> 
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