On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote:
> > This driver creates per-cpu hrtimers which are required to do the
> > periodic 'pet' operation. On a conventional watchdog-core driver, the
> > userspace is responsible for delivering the 'pet' events by writing to
> > the particular /dev/watchdogN node. In this case we require a strong
> > thread affinity to be able to account for lost time on a per vCPU.
> >
> > This part of the driver is the 'frontend' which is reponsible for
> > delivering the periodic 'pet' events, configuring the virtual peripheral
> > and listening for cpu hotplug events. The other part of the driver
> > handles the peripheral emulation and this part accounts for lost time by
> > looking at the /proc/{}/task/{}/stat entries and is located here:
> > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817
> >
> > Signed-off-by: Sebastian Ene <sebastianene@xxxxxxxxxx>
> > ---
> > drivers/misc/Kconfig | 12 +++
> > drivers/misc/Makefile | 1 +
> > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++
> > 3 files changed, 219 insertions(+)
> > create mode 100644 drivers/misc/vm-watchdog.c
> >
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 2b9572a6d114..26c3a99e269c 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -493,6 +493,18 @@ config OPEN_DICE
> >
> > If unsure, say N.
> >
> > +config VM_WATCHDOG
> > + tristate "Virtual Machine Watchdog"
> > + select LOCKUP_DETECTOR
> > + help
> > + Detect CPU locks on the virtual machine. This driver relies on the
> > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU
> > + has to do a 'pet', it exits the guest through MMIO write and the
> > + backend driver takes into account the lost ticks for this particular
> > + CPU.
Hi,
>
> There's nothing to keep this tied to a virtual machine at all, right?
> You are just relying on some iomem address to be updated, so it should
> be a "generic_iomem_watchdog" driver as there's nothing specific to vms
> at all from what I can tell.
>
> thanks,
>
> greg k-h
That's right although I might think of using the term "generic lockup detector"
instead of watchdog. The only reason why I would keep "virtual machine"
word in, is that there is no actual hardware for this.
Thanks,
Seb
