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From: Philipp Hahn <hahn@univention.de>
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Date: Wed, 20 Jan 2016 07:37:53 +0100
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Subject: Re: [Qemu-devel] how to setup a watchdog?
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To: lejeczek <peljasz@yahoo.co.uk>, qemu-devel qemu-devel <qemu-devel@nongnu.org>

Hi,

Am 18.01.2016 um 12:43 schrieb lejeczek:
> I'm trying Qemu's watchdog.
> My understanding was that hardware (here qemu's watchdog) would take
> action, eg. cold reboot the system if there is no ping from the OS
> watchdog, so I
> thought stopping watchdog service in VM should be a quick test, right?
>=20
> I have this in the guest:
>=20
>     <watchdog model=3D'i6300esb' action=3D'reset'>
>       <address type=3D'pci' domain=3D'0x0000' bus=3D'0x00' slot=3D'0x08=
' function=3D'0x0'/>
>     </watchdog>
>=20
> and I see /dev/watchdog in my guest. Yet nothing happens, guest(linux)
> runs uninterrupted.
> I must be missing something, an expert said it's config problem, is it
> really is?

Probably reading linux/Documentation/watchdog/watchdog-api.txt should
give you some extra hints.

AFAIK you need to open that device file at least once, either with the
sample program included in the Linux source tree, or by another program
like (Debian) watchdog or systemd (man 5 systemd-system.conf ->
RuntimeWatchdogSec)

  cat /dev/watchdog # will print an error about the read(), but the
important thing (opening the file) has been done
  dmesg | grep watchdog # will print "i6300esb: Unexpected close, not
stopping watchdog!" to show you that the watchdog is still running and
will trigger the reboot, as it has gone through the shutdown protocol,
which can be used to disable the watchdog again

After ~1m my test VM rebooted.

Philipp