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6c93c6f3 SE |
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> | |
6c93c6f3 SE |
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 | ||
36 | void __iomem *membase; | |
37 | struct platform_device *dev; | |
38 | enum cpuhp_state hp_online; | |
39 | }; | |
40 | ||
41 | struct vcpu_stall_priv { | |
42 | struct hrtimer vcpu_hrtimer; | |
43 | bool is_initialized; | |
44 | }; | |
45 | ||
46 | /* The vcpu stall configuration structure which applies to all the CPUs */ | |
47 | static struct vcpu_stall_detect_config vcpu_stall_config; | |
48 | ||
49 | #define vcpu_stall_reg_write(vcpu, reg, value) \ | |
50 | writel_relaxed((value), \ | |
51 | (void __iomem *)(vcpu_stall_config.membase + \ | |
52 | (vcpu) * VCPU_STALL_REG_LEN + (reg))) | |
53 | ||
54 | ||
55 | static struct vcpu_stall_priv __percpu *vcpu_stall_detectors; | |
56 | ||
57 | static enum hrtimer_restart | |
58 | vcpu_stall_detect_timer_fn(struct hrtimer *hrtimer) | |
59 | { | |
60 | u32 ticks, ping_timeout_ms; | |
61 | ||
62 | /* Reload the stall detector counter register every | |
63 | * `ping_timeout_ms` to prevent the virtual device | |
64 | * from decrementing it to 0. The virtual device decrements this | |
65 | * register at 'clock_freq_hz' frequency. | |
66 | */ | |
67 | ticks = vcpu_stall_config.clock_freq_hz * | |
68 | vcpu_stall_config.stall_timeout_sec; | |
69 | vcpu_stall_reg_write(smp_processor_id(), | |
70 | VCPU_STALL_REG_LOAD_CNT, ticks); | |
71 | ||
72 | ping_timeout_ms = vcpu_stall_config.stall_timeout_sec * | |
73 | MSEC_PER_SEC / 2; | |
74 | hrtimer_forward_now(hrtimer, | |
75 | ms_to_ktime(ping_timeout_ms)); | |
76 | ||
77 | return HRTIMER_RESTART; | |
78 | } | |
79 | ||
80 | static int start_stall_detector_cpu(unsigned int cpu) | |
81 | { | |
82 | u32 ticks, ping_timeout_ms; | |
83 | struct vcpu_stall_priv *vcpu_stall_detector = | |
84 | this_cpu_ptr(vcpu_stall_detectors); | |
85 | struct hrtimer *vcpu_hrtimer = &vcpu_stall_detector->vcpu_hrtimer; | |
86 | ||
87 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_CLOCK_FREQ_HZ, | |
88 | vcpu_stall_config.clock_freq_hz); | |
89 | ||
90 | /* Compute the number of ticks required for the stall detector | |
91 | * counter register based on the internal clock frequency and the | |
92 | * timeout value given from the device tree. | |
93 | */ | |
94 | ticks = vcpu_stall_config.clock_freq_hz * | |
95 | vcpu_stall_config.stall_timeout_sec; | |
96 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_LOAD_CNT, ticks); | |
97 | ||
98 | /* Enable the internal clock and start the stall detector */ | |
99 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 1); | |
100 | ||
101 | /* Pet the stall detector at half of its expiration timeout | |
102 | * to prevent spurious resets. | |
103 | */ | |
104 | ping_timeout_ms = vcpu_stall_config.stall_timeout_sec * | |
105 | MSEC_PER_SEC / 2; | |
106 | ||
107 | hrtimer_init(vcpu_hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
108 | vcpu_hrtimer->function = vcpu_stall_detect_timer_fn; | |
109 | vcpu_stall_detector->is_initialized = true; | |
110 | ||
111 | hrtimer_start(vcpu_hrtimer, ms_to_ktime(ping_timeout_ms), | |
112 | HRTIMER_MODE_REL_PINNED); | |
113 | ||
114 | return 0; | |
115 | } | |
116 | ||
117 | static int stop_stall_detector_cpu(unsigned int cpu) | |
118 | { | |
119 | struct vcpu_stall_priv *vcpu_stall_detector = | |
120 | per_cpu_ptr(vcpu_stall_detectors, cpu); | |
121 | ||
122 | if (!vcpu_stall_detector->is_initialized) | |
123 | return 0; | |
124 | ||
125 | /* Disable the stall detector for the current CPU */ | |
126 | hrtimer_cancel(&vcpu_stall_detector->vcpu_hrtimer); | |
127 | vcpu_stall_reg_write(cpu, VCPU_STALL_REG_STATUS, 0); | |
128 | vcpu_stall_detector->is_initialized = false; | |
129 | ||
130 | return 0; | |
131 | } | |
132 | ||
133 | static int vcpu_stall_detect_probe(struct platform_device *pdev) | |
134 | { | |
135 | int ret; | |
136 | struct resource *r; | |
137 | void __iomem *membase; | |
138 | u32 clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; | |
139 | u32 stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; | |
140 | struct device_node *np = pdev->dev.of_node; | |
141 | ||
142 | vcpu_stall_detectors = devm_alloc_percpu(&pdev->dev, | |
143 | typeof(struct vcpu_stall_priv)); | |
144 | if (!vcpu_stall_detectors) | |
145 | return -ENOMEM; | |
146 | ||
147 | membase = devm_platform_get_and_ioremap_resource(pdev, 0, &r); | |
148 | if (IS_ERR(membase)) { | |
149 | dev_err(&pdev->dev, "Failed to get memory resource\n"); | |
150 | return PTR_ERR(membase); | |
151 | } | |
152 | ||
153 | if (!of_property_read_u32(np, "clock-frequency", &clock_freq_hz)) { | |
154 | if (!(clock_freq_hz > 0 && | |
155 | clock_freq_hz < VCPU_STALL_MAX_CLOCK_HZ)) { | |
156 | dev_warn(&pdev->dev, "clk out of range\n"); | |
157 | clock_freq_hz = VCPU_STALL_DEFAULT_CLOCK_HZ; | |
158 | } | |
159 | } | |
160 | ||
161 | if (!of_property_read_u32(np, "timeout-sec", &stall_timeout_sec)) { | |
162 | if (!(stall_timeout_sec > 0 && | |
163 | stall_timeout_sec < VCPU_STALL_MAX_TIMEOUT_SEC)) { | |
164 | dev_warn(&pdev->dev, "stall timeout out of range\n"); | |
165 | stall_timeout_sec = VCPU_STALL_DEFAULT_TIMEOUT_SEC; | |
166 | } | |
167 | } | |
168 | ||
169 | vcpu_stall_config = (struct vcpu_stall_detect_config) { | |
170 | .membase = membase, | |
171 | .clock_freq_hz = clock_freq_hz, | |
172 | .stall_timeout_sec = stall_timeout_sec | |
173 | }; | |
174 | ||
175 | ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, | |
176 | "virt/vcpu_stall_detector:online", | |
177 | start_stall_detector_cpu, | |
178 | stop_stall_detector_cpu); | |
179 | if (ret < 0) { | |
180 | dev_err(&pdev->dev, "failed to install cpu hotplug"); | |
181 | goto err; | |
182 | } | |
183 | ||
184 | vcpu_stall_config.hp_online = ret; | |
185 | return 0; | |
186 | err: | |
187 | return ret; | |
188 | } | |
189 | ||
190 | static int vcpu_stall_detect_remove(struct platform_device *pdev) | |
191 | { | |
192 | int cpu; | |
193 | ||
194 | cpuhp_remove_state(vcpu_stall_config.hp_online); | |
195 | ||
196 | for_each_possible_cpu(cpu) | |
197 | stop_stall_detector_cpu(cpu); | |
198 | ||
199 | return 0; | |
200 | } | |
201 | ||
202 | static const struct of_device_id vcpu_stall_detect_of_match[] = { | |
203 | { .compatible = "qemu,vcpu-stall-detector", }, | |
204 | {} | |
205 | }; | |
206 | ||
207 | MODULE_DEVICE_TABLE(of, vcpu_stall_detect_of_match); | |
208 | ||
209 | static struct platform_driver vcpu_stall_detect_driver = { | |
210 | .probe = vcpu_stall_detect_probe, | |
211 | .remove = vcpu_stall_detect_remove, | |
212 | .driver = { | |
213 | .name = KBUILD_MODNAME, | |
214 | .of_match_table = vcpu_stall_detect_of_match, | |
215 | }, | |
216 | }; | |
217 | ||
218 | module_platform_driver(vcpu_stall_detect_driver); | |
219 | ||
220 | MODULE_LICENSE("GPL"); | |
221 | MODULE_AUTHOR("Sebastian Ene <sebastianene@google.com>"); | |
222 | MODULE_DESCRIPTION("VCPU stall detector"); |