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Message-Id: <20220405141954.1489782-3-sebastianene@google.com>
Date: Tue, 5 Apr 2022 14:19:55 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: Wim Van Sebroeck <wim@...ux-watchdog.org>,
Guenter Roeck <linux@...ck-us.net>,
Rob Herring <robh+dt@...nel.org>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-watchdog@...r.kernel.org, will@...nel.org,
qperret@...gle.com, maz@...nel.org,
Sebastian Ene <sebastianene@...gle.com>
Subject: [PATCH 2/2] watchdog: Add a mechanism to detect stalls on guest vCPUs
This patch adds support for a virtual watchdog which relies on the
per-cpu hrtimers to pet at regular intervals.
Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
drivers/watchdog/Kconfig | 8 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/vm-wdt.c | 215 ++++++++++++++++++++++++++++++++++++++
3 files changed, 224 insertions(+)
create mode 100644 drivers/watchdog/vm-wdt.c
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 01ce3f41cc21..3304d128484e 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -351,6 +351,14 @@ config SL28CPLD_WATCHDOG
To compile this driver as a module, choose M here: the
module will be called sl28cpld_wdt.
+config VM_WATCHDOG
+ tristate "Virtual Machine Watchdog"
+ select LOCKUP_DETECTOR
+ help
+ Detect CPU locks on the virtual machine.
+ To compile this driver as a module, choose M here: the
+ module will be called vm-wdt.
+
# ALPHA Architecture
# ARM Architecture
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 071a2e50be98..73206cbc3835 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -227,3 +227,4 @@ obj-$(CONFIG_MENZ069_WATCHDOG) += menz69_wdt.o
obj-$(CONFIG_RAVE_SP_WATCHDOG) += rave-sp-wdt.o
obj-$(CONFIG_STPMIC1_WATCHDOG) += stpmic1_wdt.o
obj-$(CONFIG_SL28CPLD_WATCHDOG) += sl28cpld_wdt.o
+obj-$(CONFIG_VM_WATCHDOG) += vm-wdt.o
diff --git a/drivers/watchdog/vm-wdt.c b/drivers/watchdog/vm-wdt.c
new file mode 100644
index 000000000000..ea4351754645
--- /dev/null
+++ b/drivers/watchdog/vm-wdt.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Virtual watchdog driver.
+// Copyright (C) Google, 2022
+
+#define pr_fmt(fmt) "vm-watchdog: " fmt
+
+#include <linux/cpu.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/nmi.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/param.h>
+#include <linux/percpu.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define DRV_NAME "vm_wdt"
+#define DRV_VERSION "1.0"
+
+#define VMWDT_REG_STATUS (0x00)
+#define VMWDT_REG_LOAD_CNT (0x04)
+#define VMWDT_REG_CURRENT_CNT (0x08)
+#define VMWDT_REG_CLOCK_FREQ_HZ (0x0C)
+#define VMWDT_REG_LEN (0x10)
+
+#define VMWDT_DEFAULT_CLOCK_HZ (10)
+#define VMWDT_DEFAULT_TIMEOT_SEC (8)
+
+struct vm_wdt_s {
+ void __iomem *membase;
+ u32 clock_freq;
+ u32 expiration_sec;
+ u32 ping_timeout_ms;
+ struct hrtimer per_cpu_hrtimer;
+ struct platform_device *dev;
+};
+
+#define vmwdt_reg_write(wdt, reg, value) \
+ iowrite32((value), (wdt)->membase + (reg))
+#define vmwdt_reg_read(wdt, reg) \
+ io32read((wdt)->membase + (reg))
+
+static struct platform_device *virt_dev;
+
+static enum hrtimer_restart vmwdt_timer_fn(struct hrtimer *hrtimer)
+{
+ struct vm_wdt_s *cpu_wdt;
+ u32 ticks;
+
+ cpu_wdt = container_of(hrtimer, struct vm_wdt_s, per_cpu_hrtimer);
+ ticks = cpu_wdt->clock_freq * cpu_wdt->expiration_sec;
+ vmwdt_reg_write(cpu_wdt, VMWDT_REG_LOAD_CNT, ticks);
+ hrtimer_forward_now(hrtimer, ms_to_ktime(cpu_wdt->ping_timeout_ms));
+
+ return HRTIMER_RESTART;
+}
+
+static void vmwdt_start(void *arg)
+{
+ u32 ticks;
+ int cpu = smp_processor_id();
+ struct vm_wdt_s *cpu_wdt = arg;
+ struct hrtimer *hrtimer = &cpu_wdt->per_cpu_hrtimer;
+
+ pr_info("cpu %u vmwdt start\n", cpu);
+ vmwdt_reg_write(cpu_wdt, VMWDT_REG_CLOCK_FREQ_HZ,
+ cpu_wdt->clock_freq);
+
+ /* Compute the number of ticks required for the watchdog counter
+ * register based on the internal clock frequency and the watchdog
+ * timeout given from the device tree.
+ */
+ ticks = cpu_wdt->clock_freq * cpu_wdt->expiration_sec;
+ vmwdt_reg_write(cpu_wdt, VMWDT_REG_LOAD_CNT, ticks);
+
+ /* Enable the internal clock and start the watchdog */
+ vmwdt_reg_write(cpu_wdt, VMWDT_REG_STATUS, 1);
+
+ hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ hrtimer->function = vmwdt_timer_fn;
+ hrtimer_start(hrtimer, ms_to_ktime(cpu_wdt->ping_timeout_ms),
+ HRTIMER_MODE_REL_PINNED);
+}
+
+static void vmwdt_stop(void *arg)
+{
+ int cpu = smp_processor_id();
+ struct vm_wdt_s *cpu_wdt = arg;
+ struct hrtimer *hrtimer = &cpu_wdt->per_cpu_hrtimer;
+
+ hrtimer_cancel(hrtimer);
+
+ /* Disable the watchdog */
+ vmwdt_reg_write(cpu_wdt, VMWDT_REG_STATUS, 0);
+ pr_info("cpu %d vmwdt stop\n", cpu);
+}
+
+static int start_watchdog_on_cpu(unsigned int cpu)
+{
+ struct vm_wdt_s *vm_wdt = platform_get_drvdata(virt_dev);
+
+ vmwdt_start(this_cpu_ptr(vm_wdt));
+ return 0;
+}
+
+static int stop_watchdog_on_cpu(unsigned int cpu)
+{
+ struct vm_wdt_s *vm_wdt = platform_get_drvdata(virt_dev);
+
+ vmwdt_stop(this_cpu_ptr(vm_wdt));
+ return 0;
+}
+
+static int vmwdt_probe(struct platform_device *dev)
+{
+ int cpu, ret, err;
+ void __iomem *membase;
+ struct resource *r;
+ struct vm_wdt_s *vm_wdt;
+ u32 wdt_clock, wdt_timeout_sec = 0;
+
+ r = platform_get_resource(dev, IORESOURCE_MEM, 0);
+ if (r == NULL)
+ return -ENOENT;
+
+ vm_wdt = alloc_percpu(typeof(struct vm_wdt_s));
+ if (!vm_wdt)
+ return -ENOMEM;
+
+ membase = ioremap(r->start, resource_size(r));
+ if (!membase) {
+ ret = -ENXIO;
+ goto err_withmem;
+ }
+
+ virt_dev = dev;
+ platform_set_drvdata(dev, vm_wdt);
+ if (of_property_read_u32(dev->dev.of_node, "clock", &wdt_clock))
+ wdt_clock = VMWDT_DEFAULT_CLOCK_HZ;
+
+ if (of_property_read_u32(dev->dev.of_node, "timeout-sec",
+ &wdt_timeout_sec))
+ wdt_timeout_sec = VMWDT_DEFAULT_TIMEOT_SEC;
+
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) {
+ struct vm_wdt_s *cpu_wdt = per_cpu_ptr(vm_wdt, cpu);
+
+ cpu_wdt->membase = membase + cpu * VMWDT_REG_LEN;
+ cpu_wdt->clock_freq = wdt_clock;
+ cpu_wdt->expiration_sec = wdt_timeout_sec;
+ cpu_wdt->ping_timeout_ms = wdt_timeout_sec * MSEC_PER_SEC / 2;
+ smp_call_function_single(cpu, vmwdt_start, cpu_wdt, true);
+ }
+
+ err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "virt/watchdog:online",
+ start_watchdog_on_cpu,
+ stop_watchdog_on_cpu);
+ if (err < 0) {
+ pr_warn("could not be initialized");
+ ret = err;
+ goto err_withmem;
+ }
+
+ return 0;
+
+err_withmem:
+ free_percpu(vm_wdt);
+ return ret;
+}
+
+static int vmwdt_remove(struct platform_device *dev)
+{
+ int cpu;
+ struct vm_wdt_s *vm_wdt = platform_get_drvdata(dev);
+
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) {
+ struct vm_wdt_s *cpu_wdt = per_cpu_ptr(vm_wdt, cpu);
+
+ smp_call_function_single(cpu, vmwdt_stop, cpu_wdt, true);
+ }
+
+ free_percpu(vm_wdt);
+ return 0;
+}
+
+static const struct of_device_id vmwdt_of_match[] = {
+ { .compatible = "qemu,vm-watchdog", },
+ {}
+};
+
+MODULE_DEVICE_TABLE(of, vm_watchdog_of_match);
+
+static struct platform_driver vmwdt_driver = {
+ .probe = vmwdt_probe,
+ .remove = vmwdt_remove,
+ .driver = {
+ .name = DRV_NAME,
+ .of_match_table = vmwdt_of_match,
+ },
+};
+
+module_platform_driver(vmwdt_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sebastian Ene <sebastianene@...gle.com>");
+MODULE_DESCRIPTION("Virtual watchdog driver");
+MODULE_VERSION(DRV_VERSION);
--
2.35.1.1094.g7c7d902a7c-goog
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