This is a re-work from v9 and addresses the comments received from Will. This adds a mechanism to detect stalls on the guest vCPUS by creating a per CPU hrtimer which periodically 'pets' the host backend driver. 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 basis. This device driver acts as a soft lockup detector by relying on the host backend driver to measure the elapesed time between subsequent 'pet' events. If the elapsed time doesn't match an expected value, the backend driver decides that the guest vCPU is locked and resets the guest. The host backend driver takes into account the time that the guest is not running. The communication with the backend driver is done through MMIO and the register layout of the virtual watchdog is described as part of the backend driver changes. The host backend driver is implemented as part of: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817 Changelog v10: - keep only the hrtimer and a flag in the per_cpu structure and move the other fields in a separate config structure - fix a potential race condition as pointed out by Will: the driver remove(..) can race with the hotplug cpu notifiers - replace alloc_percpu with devm_alloc_percpu and remove the free_percpu - unregister the hotplug notifiers - improve the Kconfig description and fix the license in the header file - add the review-by tag from Rob as the DT has not changed since v9 Changelog v9: - make the driver depend on CONFIG_OF - remove the platform_(set|get)_drvdata calls and keep a per-cpu static variable `vm_stall_detect` as suggested by Guenter on the (v8) series - improve commit description and fix styling Sebastian Ene (2): dt-bindings: vcpu_stall_detector: Add qemu,vcpu-stall-detector compatible misc: Add a mechanism to detect stalls on guest vCPUs .../misc/qemu,vcpu-stall-detector.yaml | 51 +++++ drivers/misc/Kconfig | 14 ++ drivers/misc/Makefile | 1 + drivers/misc/vcpu_stall_detector.c | 209 ++++++++++++++++++ 4 files changed, 275 insertions(+) create mode 100644 Documentation/devicetree/bindings/misc/qemu,vcpu-stall-detector.yaml create mode 100644 drivers/misc/vcpu_stall_detector.c -- 2.37.0.rc0.161.g10f37bed90-goog
