Messages in this thread | | | Date | Sat, 30 Apr 2022 08:18:14 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v4 2/2] misc: Add a mechanism to detect stalls on guest vCPUs |
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On Fri, Apr 29, 2022 at 09:51:51AM -0700, Guenter Roeck wrote: > On 4/29/22 01:48, 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@google.com> > > > --- > > > 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. > > > + To compile this driver as a module, choose M here: the > > > + module will be called vm-wdt. > > > > You forgot to name the module properly here based on the Makefile change > > you made. > > > > And again, as this is called a "watchdog", it seems crazy that it is not > > in drivers/watchdog/ > > > > I disagree. It is not a watchdog driver in the traditional sense (it does > not use, want to use, or need to use the watchdog driver API or ABI). > Its functionality is similar to the functionality of kernel/watchdog.c, > which doesn't belong into drivers/watchdog either.
Ah, ok, that makes more sense, the user/kernel api is not the same. Someone should put that in the changelog next time :)
thanks,
greg k-h
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