---
drivers/misc/Kconfig | 13 ++
drivers/misc/Makefile | 1 +
drivers/misc/vcpu_stall_detector.c | 212 +++++++++++++++++++++++++++++
3 files changed, 226 insertions(+)
create mode 100644 drivers/misc/vcpu_stall_detector.c
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 41d2bb0ae23a..83afb41a85cf 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -483,6 +483,19 @@ config OPEN_DICE
If unsure, say N.
+config VCPU_STALL_DETECTOR
+ tristate "VCPU stall detector"
+ select LOCKUP_DETECTOR
+ depends on OF
+ 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.
+
source "drivers/misc/c2port/Kconfig"
source "drivers/misc/eeprom/Kconfig"
source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 70e800e9127f..2be8542616dd 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -60,3 +60,4 @@ obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o
obj-$(CONFIG_HISI_HIKEY_USB) += hisi_hikey_usb.o
obj-$(CONFIG_HI6421V600_IRQ) += hi6421v600-irq.o
obj-$(CONFIG_OPEN_DICE) += open-dice.o
+obj-$(CONFIG_VCPU_STALL_DETECTOR) += vcpu_stall_detector.o
\ No newline at end of file
diff --git a/drivers/misc/vcpu_stall_detector.c b/drivers/misc/vcpu_stall_detector.c
new file mode 100644
index 000000000000..039ac54564c1
--- /dev/null
+++ b/drivers/misc/vcpu_stall_detector.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// VCPU stall detector.
+// Copyright (C) Google, 2022
+
+#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 REG_STATUS (0x00)
+#define REG_LOAD_CNT (0x04)
+#define REG_CURRENT_CNT (0x08)
+#define REG_CLOCK_FREQ_HZ (0x0C)
+#define REG_LEN (0x10)
+
+#define DEFAULT_CLOCK_HZ (10)
+#define DEFAULT_TIMEOT_SEC (8)
+
+struct vm_stall_detect_s {
+ void __iomem *membase;
+ u32 clock_freq;
+ u32 expiration_sec;
+ u32 ping_timeout_ms;
+ struct hrtimer per_cpu_hrtimer;
+ struct platform_device *dev;
+};
+
+#define vcpu_stall_detect_reg_write(stall_detect, reg, value) \
+ iowrite32((value), (stall_detect)->membase + (reg))
+#define vcpu_stall_detect_reg_read(stall_detect, reg) \
+ io32read((stall_detect)->membase + (reg))
+
+static struct vm_stall_detect_s __percpu *vm_stall_detect;
+
+static enum hrtimer_restart
+vcpu_stall_detect_timer_fn(struct hrtimer *hrtimer)
+{
+ struct vm_stall_detect_s *cpu_stall_detect;
+ u32 ticks;
+
+ cpu_stall_detect = container_of(hrtimer, struct vm_stall_detect_s,
+ per_cpu_hrtimer);
+ ticks = cpu_stall_detect->clock_freq * cpu_stall_detect->expiration_sec;
+ vcpu_stall_detect_reg_write(cpu_stall_detect, REG_LOAD_CNT, ticks);
+ hrtimer_forward_now(hrtimer,
+ ms_to_ktime(cpu_stall_detect->ping_timeout_ms));
+
+ return HRTIMER_RESTART;
+}
+
+static void vcpu_stall_detect_start(void *arg)
+{
+ u32 ticks;
+ struct vm_stall_detect_s *cpu_stall_detect = arg;
+ struct hrtimer *hrtimer = &cpu_stall_detect->per_cpu_hrtimer;
+
+ vcpu_stall_detect_reg_write(cpu_stall_detect, REG_CLOCK_FREQ_HZ,
+ cpu_stall_detect->clock_freq);
+
+ /* Compute the number of ticks required for the stall detector counter
+ * register based on the internal clock frequency and the timeout
+ * value given from the device tree.
+ */
+ ticks = cpu_stall_detect->clock_freq *
+ cpu_stall_detect->expiration_sec;
+ vcpu_stall_detect_reg_write(cpu_stall_detect, REG_LOAD_CNT, ticks);
+
+ /* Enable the internal clock and start the stall detector */
+ vcpu_stall_detect_reg_write(cpu_stall_detect, REG_STATUS, 1);
+
+ hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ hrtimer->function = vcpu_stall_detect_timer_fn;
+ hrtimer_start(hrtimer, ms_to_ktime(cpu_stall_detect->ping_timeout_ms),
+ HRTIMER_MODE_REL_PINNED);
+}
+
+static void vcpu_stall_detect_stop(void *arg)
+{
+ struct vm_stall_detect_s *cpu_stall_detect = arg;
+ struct hrtimer *hrtimer = &cpu_stall_detect->per_cpu_hrtimer;
+
+ hrtimer_cancel(hrtimer);
+
+ /* Disable the stall detector */
+ vcpu_stall_detect_reg_write(cpu_stall_detect, REG_STATUS, 0);
+}
+
+static int start_stall_detector_on_cpu(unsigned int cpu)
+{
+ vcpu_stall_detect_start(this_cpu_ptr(vm_stall_detect));
+ return 0;
+}
+
+static int stop_stall_detector_on_cpu(unsigned int cpu)
+{
+ vcpu_stall_detect_stop(this_cpu_ptr(vm_stall_detect));
+ return 0;
+}
+
+static int vcpu_stall_detect_probe(struct platform_device *dev)
+{
+ int cpu, ret, err;
+ void __iomem *membase;
+ struct resource *r;
+ u32 stall_detect_clock, stall_detect_timeout_sec = 0;
+
+ r = platform_get_resource(dev, IORESOURCE_MEM, 0);
+ if (r == NULL)
+ return -ENODEV;
+
+ vm_stall_detect = alloc_percpu(typeof(struct vm_stall_detect_s));
+ if (!vm_stall_detect)
+ return -ENOMEM;
+
+ membase = ioremap(r->start, resource_size(r));
+ if (!membase) {
+ ret = -ENOMEM;
+ goto err_withmem;
+ }
+
+ if (of_property_read_u32(dev->dev.of_node, "clock-frequency",
+ &stall_detect_clock))
+ stall_detect_clock = DEFAULT_CLOCK_HZ;
+
+ if (of_property_read_u32(dev->dev.of_node, "timeout-sec",
+ &stall_detect_timeout_sec))
+ stall_detect_timeout_sec = DEFAULT_TIMEOT_SEC;
+
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) {
+ struct vm_stall_detect_s *cpu_stall_detect;
+
+ cpu_stall_detect = per_cpu_ptr(vm_stall_detect, cpu);
+ cpu_stall_detect->membase = membase + cpu * REG_LEN;
+ cpu_stall_detect->clock_freq = stall_detect_clock;
+ cpu_stall_detect->expiration_sec = stall_detect_timeout_sec;
+
+ /* Pet the stall detector at half of its expiration timeout
+ * to prevent spurios resets.
+ */
+ cpu_stall_detect->ping_timeout_ms = stall_detect_timeout_sec *
+ MSEC_PER_SEC / 2;
+ smp_call_function_single(cpu, vcpu_stall_detect_start,
+ cpu_stall_detect, true);
+ }
+
+ err = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "virt/vcpu_stall_detector:online",
+ start_stall_detector_on_cpu,
+ stop_stall_detector_on_cpu);
+ if (err < 0) {
+ dev_err(&dev->dev, "failed to install cpu hotplug");
+ ret = err;
+ goto err_withmem;
+ }
+
+ return 0;
+
+err_withmem:
+ free_percpu(vm_stall_detect);
+ return ret;
+}
+
+static int vcpu_stall_detect_remove(struct platform_device *dev)
+{
+ int cpu;
+
+ for_each_cpu_and(cpu, cpu_online_mask, &watchdog_cpumask) {
+ struct vm_stall_detect_s *cpu_stall_detect;
+
+ cpu_stall_detect = per_cpu_ptr(vm_stall_detect, cpu);
+ smp_call_function_single(cpu, vcpu_stall_detect_stop,
+ cpu_stall_detect, true);
+ }
+
+ free_percpu(vm_stall_detect);
+ vm_stall_detect = NULL;
+ return 0;
+}
+
+static const struct of_device_id vcpu_stall_detect_of_match[] = {
+ { .compatible = "qemu,vcpu-stall-detector", },
+ {}
+};
+
+MODULE_DEVICE_TABLE(of, vcpu_stall_detect_of_match);
+
+static struct platform_driver vcpu_stall_detect_driver = {
+ .probe = vcpu_stall_detect_probe,
+ .remove = vcpu_stall_detect_remove,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = vcpu_stall_detect_of_match,
+ },
+};
+
+module_platform_driver(vcpu_stall_detect_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sebastian Ene <sebastianene@xxxxxxxxxx>");
+MODULE_DESCRIPTION("VCPU stall detector");
