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 
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 
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 
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 
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 
97 static bool haltpoll_want(void)
98 {
99 	return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
100 }
101 
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 
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