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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/of_device.h> | |
17 | #include <linux/param.h> | |
18 | #include <linux/percpu.h> | |
19 | #include <linux/platform_device.h> | |
20 | #include <linux/slab.h> | |
21 | ||
22 | #define VCPU_STALL_REG_STATUS (0x00) | |
23 | #define VCPU_STALL_REG_LOAD_CNT (0x04) | |
24 | #define VCPU_STALL_REG_CURRENT_CNT (0x08) | |
25 | #define VCPU_STALL_REG_CLOCK_FREQ_HZ (0x0C) | |
26 | #define VCPU_STALL_REG_LEN (0x10) | |
27 | ||
28 | #define VCPU_STALL_DEFAULT_CLOCK_HZ (10) | |
29 | #define VCPU_STALL_MAX_CLOCK_HZ (100) | |
30 | #define VCPU_STALL_DEFAULT_TIMEOUT_SEC (8) | |
31 | #define VCPU_STALL_MAX_TIMEOUT_SEC (600) | |
32 | ||
33 | struct vcpu_stall_detect_config { | |
34 | u32 clock_freq_hz; | |
35 | u32 stall_timeout_sec; | |
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 int start_stall_detector_cpu(unsigned int cpu) | |
82 | { | |
83 | u32 ticks, ping_timeout_ms; | |
84 | struct vcpu_stall_priv *vcpu_stall_detector = | |
85 | this_cpu_ptr(vcpu_stall_detectors); | |
86 | struct hrtimer *vcpu_hrtimer = &vcpu_stall_detector->vcpu_hrtimer; | |
87 | ||
88 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_CLOCK_FREQ_HZ, | |
89 | vcpu_stall_config.clock_freq_hz); | |
90 | ||
91 | /* Compute the number of ticks required for the stall detector | |
92 | * counter register based on the internal clock frequency and the | |
93 | * timeout value given from the device tree. | |
94 | */ | |
95 | ticks = vcpu_stall_config.clock_freq_hz * | |
96 | vcpu_stall_config.stall_timeout_sec; | |
97 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_LOAD_CNT, ticks); | |
98 | ||
99 | /* Enable the internal clock and start the stall detector */ | |
100 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 1); | |
101 | ||
102 | /* Pet the stall detector at half of its expiration timeout | |
103 | * to prevent spurious resets. | |
104 | */ | |
105 | ping_timeout_ms = vcpu_stall_config.stall_timeout_sec * | |
106 | MSEC_PER_SEC / 2; | |
107 | ||
108 | hrtimer_init(vcpu_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
109 | vcpu_hrtimer->function = vcpu_stall_detect_timer_fn; | |
110 | vcpu_stall_detector->is_initialized = true; | |
111 | ||
112 | hrtimer_start(vcpu_hrtimer, ms_to_ktime(ping_timeout_ms), | |
113 | HRTIMER_MODE_REL_PINNED); | |
114 | ||
115 | return 0; | |
116 | } | |
117 | ||
118 | static int stop_stall_detector_cpu(unsigned int cpu) | |
119 | { | |
120 | struct vcpu_stall_priv *vcpu_stall_detector = | |
121 | per_cpu_ptr(vcpu_stall_detectors, cpu); | |
122 | ||
123 | if (!vcpu_stall_detector->is_initialized) | |
124 | return 0; | |
125 | ||
126 | /* Disable the stall detector for the current CPU */ | |
127 | hrtimer_cancel(&vcpu_stall_detector->vcpu_hrtimer); | |
128 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 0); | |
129 | vcpu_stall_detector->is_initialized = false; | |
130 | ||
131 | return 0; | |
132 | } | |
133 | ||
134 | static int vcpu_stall_detect_probe(struct platform_device *pdev) | |
135 | { | |
136 | int ret; | |
137 | struct resource *r; | |
138 | void __iomem *membase; | |
139 | u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; | |
140 | u32 stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; | |
141 | struct device_node *np = pdev->dev.of_node; | |
142 | ||
143 | vcpu_stall_detectors = devm_alloc_percpu(&pdev->dev, | |
144 | typeof(struct vcpu_stall_priv)); | |
145 | if (!vcpu_stall_detectors) | |
146 | return -ENOMEM; | |
147 | ||
148 | membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r); | |
149 | if (IS_ERR(membase)) { | |
150 | dev_err(&pdev->dev, "Failed to get memory resource\n"); | |
151 | return PTR_ERR(membase); | |
152 | } | |
153 | ||
154 | if (!of_property_read_u32(np, "clock-frequency", &clock_freq_hz)) { | |
155 | if (!(clock_freq_hz > 0 && | |
156 | clock_freq_hz < VCPU_STALL_MAX_CLOCK_HZ)) { | |
157 | dev_warn(&pdev->dev, "clk out of range\n"); | |
158 | clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; | |
159 | } | |
160 | } | |
161 | ||
162 | if (!of_property_read_u32(np, "timeout-sec", &stall_timeout_sec)) { | |
163 | if (!(stall_timeout_sec > 0 && | |
164 | stall_timeout_sec < VCPU_STALL_MAX_TIMEOUT_SEC)) { | |
165 | dev_warn(&pdev->dev, "stall timeout out of range\n"); | |
166 | stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; | |
167 | } | |
168 | } | |
169 | ||
170 | vcpu_stall_config = (struct vcpu_stall_detect_config) { | |
171 | .membase = membase, | |
172 | .clock_freq_hz = clock_freq_hz, | |
173 | .stall_timeout_sec = stall_timeout_sec | |
174 | }; | |
175 | ||
176 | ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, | |
177 | "virt/vcpu_stall_detector:online", | |
178 | start_stall_detector_cpu, | |
179 | stop_stall_detector_cpu); | |
180 | if (ret < 0) { | |
181 | dev_err(&pdev->dev, "failed to install cpu hotplug"); | |
182 | goto err; | |
183 | } | |
184 | ||
185 | vcpu_stall_config.hp_online = ret; | |
186 | return 0; | |
187 | err: | |
188 | return ret; | |
189 | } | |
190 | ||
191 | static int vcpu_stall_detect_remove(struct platform_device *pdev) | |
192 | { | |
193 | int cpu; | |
194 | ||
195 | cpuhp_remove_state(vcpu_stall_config.hp_online); | |
196 | ||
197 | for_each_possible_cpu(cpu) | |
198 | stop_stall_detector_cpu(cpu); | |
199 | ||
200 | return 0; | |
201 | } | |
202 | ||
203 | static const struct of_device_id vcpu_stall_detect_of_match[] = { | |
204 | { .compatible = "qemu,vcpu-stall-detector", }, | |
205 | {} | |
206 | }; | |
207 | ||
208 | MODULE_DEVICE_TABLE(of, vcpu_stall_detect_of_match); | |
209 | ||
210 | static struct platform_driver vcpu_stall_detect_driver = { | |
211 | .probe = vcpu_stall_detect_probe, | |
212 | .remove = vcpu_stall_detect_remove, | |
213 | .driver = { | |
214 | .name = KBUILD_MODNAME, | |
215 | .of_match_table = vcpu_stall_detect_of_match, | |
216 | }, | |
217 | }; | |
218 | ||
219 | module_platform_driver(vcpu_stall_detect_driver); | |
220 | ||
221 | MODULE_LICENSE("GPL"); | |
222 | MODULE_AUTHOR("Sebastian Ene <sebastianene@google.com>"); | |
223 | MODULE_DESCRIPTION("VCPU stall detector"); |