Re: [PATCH v7 2/2] misc: Add a mechanism to detect stalls on guest vCPUs

[Greg Kroah-Hartman]

On Tue, Jun 21, 2022 at 08:03:09AM +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/vcpu_stall_detector.c | 222 +++++++++++++++++++++++++++++
>  3 files changed, 235 insertions(+)
>  create mode 100644 drivers/misc/vcpu_stall_detector.c
> 
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 41d2bb0ae23a..e15c85d74c4b 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -483,6 +483,18 @@ config OPEN_DICE
>  
>  	  If unsure, say N.
>  
> +config VCPU_STALL_DETECTOR
> +	tristate "VCPU stall detector"
> +	select LOCKUP_DETECTOR
> +	help
> +	  Detect CPU locks on a kvm 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 vcpu_stall_detector.

Should this depend on KVM_GUEST?

thanks,

greg k-h