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