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 v4: - rename the source from vm-wdt.c -> vm-watchdog.c - convert all the error logging calls from pr_* to dev_* calls - rename the DTS node "clock" to "clock-frequency" Changelog v3: - cosmetic fixes, remove pr_info and version information - improve description in the commit messag - improve description in the Kconfig help section Sebastian Ene (2): dt-bindings: vm-wdt: Add qemu,vm-watchdog compatible misc: Add a mechanism to detect stalls on guest vCPUs .../devicetree/bindings/misc/vm-watchdog.yaml | 45 ++++ drivers/misc/Kconfig | 12 + drivers/misc/Makefile | 1 + drivers/misc/vm-watchdog.c | 206 ++++++++++++++++++ 4 files changed, 264 insertions(+) create mode 100644 Documentation/devicetree/bindings/misc/vm-watchdog.yaml create mode 100644 drivers/misc/vm-watchdog.c -- 2.36.0.464.gb9c8b46e94-goog
