1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * cpuidle driver for haltpoll governor.
4 *
5 * Copyright 2019 Red Hat, Inc. and/or its affiliates.
6 *
7 * This work is licensed under the terms of the GNU GPL, version 2. See
8 * the COPYING file in the top-level directory.
9 *
10 * Authors: Marcelo Tosatti <mtosatti@redhat.com>
11 */
12
13 #include <linux/init.h>
14 #include <linux/cpu.h>
15 #include <linux/cpuidle.h>
16 #include <linux/module.h>
17 #include <linux/sched/idle.h>
18 #include <linux/kvm_para.h>
19 #include <linux/cpuidle_haltpoll.h>
20
21 static bool force __read_mostly;
22 module_param(force, bool, 0444);
23 MODULE_PARM_DESC(force, "Load unconditionally");
24
25 static struct cpuidle_device __percpu *haltpoll_cpuidle_devices;
26 static enum cpuhp_state haltpoll_hp_state;
27
default_enter_idle(struct cpuidle_device * dev,struct cpuidle_driver * drv,int index)28 static int default_enter_idle(struct cpuidle_device *dev,
29 struct cpuidle_driver *drv, int index)
30 {
31 if (current_clr_polling_and_test()) {
32 local_irq_enable();
33 return index;
34 }
35 arch_cpu_idle();
36 return index;
37 }
38
39 static struct cpuidle_driver haltpoll_driver = {
40 .name = "haltpoll",
41 .governor = "haltpoll",
42 .states = {
43 { /* entry 0 is for polling */ },
44 {
45 .enter = default_enter_idle,
46 .exit_latency = 1,
47 .target_residency = 1,
48 .power_usage = -1,
49 .name = "haltpoll idle",
50 .desc = "default architecture idle",
51 },
52 },
53 .safe_state_index = 0,
54 .state_count = 2,
55 };
56
haltpoll_cpu_online(unsigned int cpu)57 static int haltpoll_cpu_online(unsigned int cpu)
58 {
59 struct cpuidle_device *dev;
60
61 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
62 if (!dev->registered) {
63 dev->cpu = cpu;
64 if (cpuidle_register_device(dev)) {
65 pr_notice("cpuidle_register_device %d failed!\n", cpu);
66 return -EIO;
67 }
68 arch_haltpoll_enable(cpu);
69 }
70
71 return 0;
72 }
73
haltpoll_cpu_offline(unsigned int cpu)74 static int haltpoll_cpu_offline(unsigned int cpu)
75 {
76 struct cpuidle_device *dev;
77
78 dev = per_cpu_ptr(haltpoll_cpuidle_devices, cpu);
79 if (dev->registered) {
80 arch_haltpoll_disable(cpu);
81 cpuidle_unregister_device(dev);
82 }
83
84 return 0;
85 }
86
haltpoll_uninit(void)87 static void haltpoll_uninit(void)
88 {
89 if (haltpoll_hp_state)
90 cpuhp_remove_state(haltpoll_hp_state);
91 cpuidle_unregister_driver(&haltpoll_driver);
92
93 free_percpu(haltpoll_cpuidle_devices);
94 haltpoll_cpuidle_devices = NULL;
95 }
96
haltpoll_want(void)97 static bool haltpoll_want(void)
98 {
99 return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
100 }
101
haltpoll_init(void)102 static int __init haltpoll_init(void)
103 {
104 int ret;
105 struct cpuidle_driver *drv = &haltpoll_driver;
106
107 /* Do not load haltpoll if idle= is passed */
108 if (boot_option_idle_override != IDLE_NO_OVERRIDE)
109 return -ENODEV;
110
111 if (!kvm_para_available() || !haltpoll_want())
112 return -ENODEV;
113
114 cpuidle_poll_state_init(drv);
115
116 ret = cpuidle_register_driver(drv);
117 if (ret < 0)
118 return ret;
119
120 haltpoll_cpuidle_devices = alloc_percpu(struct cpuidle_device);
121 if (haltpoll_cpuidle_devices == NULL) {
122 cpuidle_unregister_driver(drv);
123 return -ENOMEM;
124 }
125
126 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "cpuidle/haltpoll:online",
127 haltpoll_cpu_online, haltpoll_cpu_offline);
128 if (ret < 0) {
129 haltpoll_uninit();
130 } else {
131 haltpoll_hp_state = ret;
132 ret = 0;
133 }
134
135 return ret;
136 }
137
haltpoll_exit(void)138 static void __exit haltpoll_exit(void)
139 {
140 haltpoll_uninit();
141 }
142
143 module_init(haltpoll_init);
144 module_exit(haltpoll_exit);
145 MODULE_LICENSE("GPL");
146 MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
147