Messages in this thread |  | | Date | Sat, 30 Apr 2022 05:36:50 -0700 | Subject | Re: [PATCH v4 2/2] misc: Add a mechanism to detect stalls on guest vCPUs | From | Guenter Roeck <> |
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On 4/29/22 23:18, Greg Kroah-Hartman wrote: > 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 :) >
Renaming it to "VCPU stall detector" or similar should fix the confusion.
Guenter
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