On Tue, Mar 15, 2022 at 10:39:50AM +0000, lejeczek wrote:> Hi guys. > > Without explicitly, manually using watchdog device for a VM, the VM (centOS > 8 Stream 4.18.0-365.el8.x86_64) shows '/dev/watchdog' exists. > To double check - 'dumpxml' does not show any such device - what kind of a > 'watchdog' that is?The kernel can always provide a pure software watchdog IIRC. It can be useful if a userspace app wants a watchdog. The limitation is that it relies on the kernel remaining functional, as there's no hardware backing it up. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
On 15/03/2022 11:21, Daniel P. Berrang? wrote:> On Tue, Mar 15, 2022 at 10:39:50AM +0000, lejeczek wrote: >> Hi guys. >> >> Without explicitly, manually using watchdog device for a VM, the VM (centOS >> 8 Stream 4.18.0-365.el8.x86_64) shows '/dev/watchdog' exists. >> To double check - 'dumpxml' does not show any such device - what kind of a >> 'watchdog' that is? > The kernel can always provide a pure software watchdog IIRC. It can be > useful if a userspace app wants a watchdog. The limitation is that it > relies on the kernel remaining functional, as there's no hardware > backing it up. > > Regards, > Danielmany thanks Daniel Is qemu's watchdog configurable just like on bare-metal? Perhaps same very way - via/in BIOS? L.
On 15/03/2022 11:21, Daniel P. Berrang? wrote:> On Tue, Mar 15, 2022 at 10:39:50AM +0000, lejeczek wrote: >> Hi guys. >> >> Without explicitly, manually using watchdog device for a VM, the VM (centOS >> 8 Stream 4.18.0-365.el8.x86_64) shows '/dev/watchdog' exists. >> To double check - 'dumpxml' does not show any such device - what kind of a >> 'watchdog' that is? > The kernel can always provide a pure software watchdog IIRC. It can be > useful if a userspace app wants a watchdog. The limitation is that it > relies on the kernel remaining functional, as there's no hardware > backing it up. > > Regards, > DanielOn a related note - with 'i6300esb' watchdog which I tested and I believe is working. I get often in my VMs from 'dmesg': ... watchdog: BUG: soft lockup - CPU#0 stuck for xxxs! [swapper/0:0] rcu: INFO: rcu_sched self-detected stall on CPU ... This above is from Ubuntu and CentOS alike and when this happens, console via VNC responds to until first 'enter' then is non-resposive. This happens after VM(s) was migrated between hosts, but anyway.. I do not see what I expected from 'watchdog' - there is no action whatsoever, which should be 'reset'. VM remains in such 'frozen' state forever. any & all shared thoughts much appreciated. L.