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// 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;
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 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_init(vcpu_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
vcpu_hrtimer->function = vcpu_stall_detect_timer_fn;
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;
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
};
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:
return ret;
}
static void vcpu_stall_detect_remove(struct platform_device *pdev)
{
int cpu;
cpuhp_remove_state(vcpu_stall_config.hp_online);
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_new = 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@google.com>");
MODULE_DESCRIPTION("VCPU stall detector");
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