Quelle  vcpu_stall_detector.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
//
// 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/param.h>
#include <linux/percpu.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

#define VCPU_STALL_REG_STATUS  (0x00)
#define VCPU_STALL_REG_LOAD_CNT  (0x04)
#define VCPU_STALL_REG_CURRENT_CNT (0x08)
#define VCPU_STALL_REG_CLOCK_FREQ_HZ (0x0C)
#define VCPU_STALL_REG_LEN  (0x10)

#define VCPU_STALL_DEFAULT_CLOCK_HZ (10)
#define VCPU_STALL_MAX_CLOCK_HZ  (100)
#define VCPU_STALL_DEFAULT_TIMEOUT_SEC (8)
#define VCPU_STALL_MAX_TIMEOUT_SEC (600)

struct vcpu_stall_detect_config {
 u32 clock_freq_hz;
 u32 stall_timeout_sec;
 int ppi_irq;

 void __iomem *membase;
 struct platform_device *dev;
 enum cpuhp_state hp_online;
};

struct vcpu_stall_priv {
 struct hrtimer vcpu_hrtimer;
 bool is_initialized;
};

/* The vcpu stall configuration structure which applies to all the CPUs */
static struct vcpu_stall_detect_config vcpu_stall_config;

#define vcpu_stall_reg_write(vcpu, reg, value)    \
 writel_relaxed((value),      \
         (void __iomem *)(vcpu_stall_config.membase + \
         (vcpu) * VCPU_STALL_REG_LEN + (reg)))


static struct vcpu_stall_priv __percpu *vcpu_stall_detectors;

static enum hrtimer_restart
vcpu_stall_detect_timer_fn(struct hrtimer *hrtimer)
{
 u32 ticks, ping_timeout_ms;

 /* Reload the stall detector counter register every
 * `ping_timeout_ms` to prevent the virtual device
 * from decrementing it to 0. The virtual device decrements this
 * register at 'clock_freq_hz' frequency.
 */
 ticks = vcpu_stall_config.clock_freq_hz *
  vcpu_stall_config.stall_timeout_sec;
 vcpu_stall_reg_write(smp_processor_id(),
        VCPU_STALL_REG_LOAD_CNT, ticks);

 ping_timeout_ms = vcpu_stall_config.stall_timeout_sec *
     MSEC_PER_SEC / 2;
 hrtimer_forward_now(hrtimer,
       ms_to_ktime(ping_timeout_ms));

 return HRTIMER_RESTART;
}

static irqreturn_t vcpu_stall_detector_irq(int irq, void *dev)
{
 panic("vCPU stall detector");
 return IRQ_HANDLED;
}

static int start_stall_detector_cpu(unsigned int cpu)
{
 u32 ticks, ping_timeout_ms;
 struct vcpu_stall_priv *vcpu_stall_detector =
  this_cpu_ptr(vcpu_stall_detectors);
 struct hrtimer *vcpu_hrtimer = &vcpu_stall_detector->vcpu_hrtimer;

 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_CLOCK_FREQ_HZ,
        vcpu_stall_config.clock_freq_hz);

 /* 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 = vcpu_stall_config.clock_freq_hz *
  vcpu_stall_config.stall_timeout_sec;
 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_LOAD_CNT, ticks);

 /* Enable the internal clock and start the stall detector */
 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 1);

 /* Pet the stall detector at half of its expiration timeout
 * to prevent spurious resets.
 */
 ping_timeout_ms = vcpu_stall_config.stall_timeout_sec *
     MSEC_PER_SEC / 2;

 hrtimer_setup(vcpu_hrtimer, vcpu_stall_detect_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 vcpu_stall_detector->is_initialized = true;

 hrtimer_start(vcpu_hrtimer, ms_to_ktime(ping_timeout_ms),
        HRTIMER_MODE_REL_PINNED);

 return 0;
}

static int stop_stall_detector_cpu(unsigned int cpu)
{
 struct vcpu_stall_priv *vcpu_stall_detector =
  per_cpu_ptr(vcpu_stall_detectors, cpu);

 if (!vcpu_stall_detector->is_initialized)
  return 0;

 /* Disable the stall detector for the current CPU */
 hrtimer_cancel(&vcpu_stall_detector->vcpu_hrtimer);
 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 0);
 vcpu_stall_detector->is_initialized = false;

 return 0;
}

static int vcpu_stall_detect_probe(struct platform_device *pdev)
{
 int ret, irq;
 struct resource *r;
 void __iomem *membase;
 u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ;
 u32 stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC;
 struct device_node *np = pdev->dev.of_node;

 vcpu_stall_detectors = devm_alloc_percpu(&pdev->dev,
       typeof(struct vcpu_stall_priv));
 if (!vcpu_stall_detectors)
  return -ENOMEM;

 membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r);
 if (IS_ERR(membase)) {
  dev_err(&pdev->dev, "Failed to get memory resource\n");
  return PTR_ERR(membase);
 }

 if (!of_property_read_u32(np, "clock-frequency", &clock_freq_hz)) {
  if (!(clock_freq_hz > 0 &&
        clock_freq_hz < VCPU_STALL_MAX_CLOCK_HZ)) {
   dev_warn(&pdev->dev, "clk out of range\n");
   clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ;
  }
 }

 if (!of_property_read_u32(np, "timeout-sec", &stall_timeout_sec)) {
  if (!(stall_timeout_sec > 0 &&
        stall_timeout_sec < VCPU_STALL_MAX_TIMEOUT_SEC)) {
   dev_warn(&pdev->dev, "stall timeout out of range\n");
   stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC;
  }
 }

 vcpu_stall_config = (struct vcpu_stall_detect_config) {
  .membase  = membase,
  .clock_freq_hz  = clock_freq_hz,
  .stall_timeout_sec = stall_timeout_sec,
  .ppi_irq  = -1,
 };

 irq = platform_get_irq_optional(pdev, 0);
 if (irq > 0) {
  ret = request_percpu_irq(irq,
      vcpu_stall_detector_irq,
      "vcpu_stall_detector",
      vcpu_stall_detectors);
  if (ret)
   goto err;

  vcpu_stall_config.ppi_irq = irq;
 }

 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
    "virt/vcpu_stall_detector:online",
    start_stall_detector_cpu,
    stop_stall_detector_cpu);
 if (ret < 0) {
  dev_err(&pdev->dev, "failed to install cpu hotplug");
  goto err;
 }

 vcpu_stall_config.hp_online = ret;
 return 0;
err:
 if (vcpu_stall_config.ppi_irq > 0)
  free_percpu_irq(vcpu_stall_config.ppi_irq,
    vcpu_stall_detectors);
 return ret;
}

static void vcpu_stall_detect_remove(struct platform_device *pdev)
{
 int cpu;

 cpuhp_remove_state(vcpu_stall_config.hp_online);

 if (vcpu_stall_config.ppi_irq > 0)
  free_percpu_irq(vcpu_stall_config.ppi_irq,
    vcpu_stall_detectors);

 for_each_possible_cpu(cpu)
  stop_stall_detector_cpu(cpu);
}

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 ");
MODULE_DESCRIPTION("VCPU stall detector");