1 // SPDX-License-Identifier: GPL-2.0-only 2 // 3 // VCPU stall detector. 4 // Copyright (C) Google, 2022 5 6 #include <linux/cpu.h> 7 #include <linux/init.h> 8 #include <linux/io.h> 9 #include <linux/kernel.h> 10 11 #include <linux/device.h> 12 #include <linux/interrupt.h> 13 #include <linux/module.h> 14 #include <linux/nmi.h> 15 #include <linux/of.h> 16 #include <linux/param.h> 17 #include <linux/percpu.h> 18 #include <linux/platform_device.h> 19 #include <linux/slab.h> 20 21 #define VCPU_STALL_REG_STATUS (0x00) 22 #define VCPU_STALL_REG_LOAD_CNT (0x04) 23 #define VCPU_STALL_REG_CURRENT_CNT (0x08) 24 #define VCPU_STALL_REG_CLOCK_FREQ_HZ (0x0C) 25 #define VCPU_STALL_REG_LEN (0x10) 26 27 #define VCPU_STALL_DEFAULT_CLOCK_HZ (10) 28 #define VCPU_STALL_MAX_CLOCK_HZ (100) 29 #define VCPU_STALL_DEFAULT_TIMEOUT_SEC (8) 30 #define VCPU_STALL_MAX_TIMEOUT_SEC (600) 31 32 struct vcpu_stall_detect_config { 33 u32 clock_freq_hz; 34 u32 stall_timeout_sec; 35 int ppi_irq; 36 37 void __iomem *membase; 38 struct platform_device *dev; 39 enum cpuhp_state hp_online; 40 }; 41 42 struct vcpu_stall_priv { 43 struct hrtimer vcpu_hrtimer; 44 bool is_initialized; 45 }; 46 47 /* The vcpu stall configuration structure which applies to all the CPUs */ 48 static struct vcpu_stall_detect_config vcpu_stall_config; 49 50 #define vcpu_stall_reg_write(vcpu, reg, value) \ 51 writel_relaxed((value), \ 52 (void __iomem *)(vcpu_stall_config.membase + \ 53 (vcpu) * VCPU_STALL_REG_LEN + (reg))) 54 55 56 static struct vcpu_stall_priv __percpu *vcpu_stall_detectors; 57 58 static enum hrtimer_restart 59 vcpu_stall_detect_timer_fn(struct hrtimer *hrtimer) 60 { 61 u32 ticks, ping_timeout_ms; 62 63 /* Reload the stall detector counter register every 64 * `ping_timeout_ms` to prevent the virtual device 65 * from decrementing it to 0. The virtual device decrements this 66 * register at 'clock_freq_hz' frequency. 67 */ 68 ticks = vcpu_stall_config.clock_freq_hz * 69 vcpu_stall_config.stall_timeout_sec; 70 vcpu_stall_reg_write(smp_processor_id(), 71 VCPU_STALL_REG_LOAD_CNT, ticks); 72 73 ping_timeout_ms = vcpu_stall_config.stall_timeout_sec * 74 MSEC_PER_SEC / 2; 75 hrtimer_forward_now(hrtimer, 76 ms_to_ktime(ping_timeout_ms)); 77 78 return HRTIMER_RESTART; 79 } 80 81 static irqreturn_t vcpu_stall_detector_irq(int irq, void *dev) 82 { 83 panic("vCPU stall detector"); 84 return IRQ_HANDLED; 85 } 86 87 static int start_stall_detector_cpu(unsigned int cpu) 88 { 89 u32 ticks, ping_timeout_ms; 90 struct vcpu_stall_priv *vcpu_stall_detector = 91 this_cpu_ptr(vcpu_stall_detectors); 92 struct hrtimer *vcpu_hrtimer = &vcpu_stall_detector->vcpu_hrtimer; 93 94 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_CLOCK_FREQ_HZ, 95 vcpu_stall_config.clock_freq_hz); 96 97 /* Compute the number of ticks required for the stall detector 98 * counter register based on the internal clock frequency and the 99 * timeout value given from the device tree. 100 */ 101 ticks = vcpu_stall_config.clock_freq_hz * 102 vcpu_stall_config.stall_timeout_sec; 103 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_LOAD_CNT, ticks); 104 105 /* Enable the internal clock and start the stall detector */ 106 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 1); 107 108 /* Pet the stall detector at half of its expiration timeout 109 * to prevent spurious resets. 110 */ 111 ping_timeout_ms = vcpu_stall_config.stall_timeout_sec * 112 MSEC_PER_SEC / 2; 113 114 hrtimer_setup(vcpu_hrtimer, vcpu_stall_detect_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 115 vcpu_stall_detector->is_initialized = true; 116 117 hrtimer_start(vcpu_hrtimer, ms_to_ktime(ping_timeout_ms), 118 HRTIMER_MODE_REL_PINNED); 119 120 return 0; 121 } 122 123 static int stop_stall_detector_cpu(unsigned int cpu) 124 { 125 struct vcpu_stall_priv *vcpu_stall_detector = 126 per_cpu_ptr(vcpu_stall_detectors, cpu); 127 128 if (!vcpu_stall_detector->is_initialized) 129 return 0; 130 131 /* Disable the stall detector for the current CPU */ 132 hrtimer_cancel(&vcpu_stall_detector->vcpu_hrtimer); 133 vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 0); 134 vcpu_stall_detector->is_initialized = false; 135 136 return 0; 137 } 138 139 static int vcpu_stall_detect_probe(struct platform_device *pdev) 140 { 141 int ret, irq; 142 struct resource *r; 143 void __iomem *membase; 144 u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; 145 u32 stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; 146 struct device_node *np = pdev->dev.of_node; 147 148 vcpu_stall_detectors = devm_alloc_percpu(&pdev->dev, 149 typeof(struct vcpu_stall_priv)); 150 if (!vcpu_stall_detectors) 151 return -ENOMEM; 152 153 membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r); 154 if (IS_ERR(membase)) { 155 dev_err(&pdev->dev, "Failed to get memory resource\n"); 156 return PTR_ERR(membase); 157 } 158 159 if (!of_property_read_u32(np, "clock-frequency", &clock_freq_hz)) { 160 if (!(clock_freq_hz > 0 && 161 clock_freq_hz < VCPU_STALL_MAX_CLOCK_HZ)) { 162 dev_warn(&pdev->dev, "clk out of range\n"); 163 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; 164 } 165 } 166 167 if (!of_property_read_u32(np, "timeout-sec", &stall_timeout_sec)) { 168 if (!(stall_timeout_sec > 0 && 169 stall_timeout_sec < VCPU_STALL_MAX_TIMEOUT_SEC)) { 170 dev_warn(&pdev->dev, "stall timeout out of range\n"); 171 stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; 172 } 173 } 174 175 vcpu_stall_config = (struct vcpu_stall_detect_config) { 176 .membase = membase, 177 .clock_freq_hz = clock_freq_hz, 178 .stall_timeout_sec = stall_timeout_sec, 179 .ppi_irq = -1, 180 }; 181 182 irq = platform_get_irq_optional(pdev, 0); 183 if (irq > 0) { 184 ret = request_percpu_irq(irq, 185 vcpu_stall_detector_irq, 186 "vcpu_stall_detector", 187 vcpu_stall_detectors); 188 if (ret) 189 goto err; 190 191 vcpu_stall_config.ppi_irq = irq; 192 } 193 194 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, 195 "virt/vcpu_stall_detector:online", 196 start_stall_detector_cpu, 197 stop_stall_detector_cpu); 198 if (ret < 0) { 199 dev_err(&pdev->dev, "failed to install cpu hotplug"); 200 goto err; 201 } 202 203 vcpu_stall_config.hp_online = ret; 204 return 0; 205 err: 206 if (vcpu_stall_config.ppi_irq > 0) 207 free_percpu_irq(vcpu_stall_config.ppi_irq, 208 vcpu_stall_detectors); 209 return ret; 210 } 211 212 static void vcpu_stall_detect_remove(struct platform_device *pdev) 213 { 214 int cpu; 215 216 cpuhp_remove_state(vcpu_stall_config.hp_online); 217 218 if (vcpu_stall_config.ppi_irq > 0) 219 free_percpu_irq(vcpu_stall_config.ppi_irq, 220 vcpu_stall_detectors); 221 222 for_each_possible_cpu(cpu) 223 stop_stall_detector_cpu(cpu); 224 } 225 226 static const struct of_device_id vcpu_stall_detect_of_match[] = { 227 { .compatible = "qemu,vcpu-stall-detector", }, 228 {} 229 }; 230 231 MODULE_DEVICE_TABLE(of, vcpu_stall_detect_of_match); 232 233 static struct platform_driver vcpu_stall_detect_driver = { 234 .probe = vcpu_stall_detect_probe, 235 .remove = vcpu_stall_detect_remove, 236 .driver = { 237 .name = KBUILD_MODNAME, 238 .of_match_table = vcpu_stall_detect_of_match, 239 }, 240 }; 241 242 module_platform_driver(vcpu_stall_detect_driver); 243 244 MODULE_LICENSE("GPL"); 245 MODULE_AUTHOR("Sebastian Ene <sebastianene@google.com>"); 246 MODULE_DESCRIPTION("VCPU stall detector"); 247