1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 *
  4 * Copyright (C) 2013 Citrix Systems
  5 *
  6 * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
  7 */
  8
  9#define pr_fmt(fmt) "arm-pv: " fmt
 10
 11#include <linux/arm-smccc.h>
 12#include <linux/cpuhotplug.h>
 13#include <linux/export.h>
 14#include <linux/io.h>
 15#include <linux/jump_label.h>
 16#include <linux/printk.h>
 17#include <linux/psci.h>
 18#include <linux/reboot.h>
 19#include <linux/slab.h>
 20#include <linux/types.h>
 21#include <linux/static_call.h>
 22
 23#include <asm/paravirt.h>
 24#include <asm/pvclock-abi.h>
 25#include <asm/smp_plat.h>
 26
 27struct static_key paravirt_steal_enabled;
 28struct static_key paravirt_steal_rq_enabled;
 29
 30static u64 native_steal_clock(int cpu)
 31{
 32	return 0;
 33}
 34
 35DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
 36
 37struct pv_time_stolen_time_region {
 38	struct pvclock_vcpu_stolen_time __rcu *kaddr;
 39};
 40
 41static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
 42
 43static bool steal_acc = true;
 44static int __init parse_no_stealacc(char *arg)
 45{
 46	steal_acc = false;
 47	return 0;
 48}
 49
 50early_param("no-steal-acc", parse_no_stealacc);
 51
 52/* return stolen time in ns by asking the hypervisor */
 53static u64 para_steal_clock(int cpu)
 54{
 55	struct pvclock_vcpu_stolen_time *kaddr = NULL;
 56	struct pv_time_stolen_time_region *reg;
 57	u64 ret = 0;
 58
 59	reg = per_cpu_ptr(&stolen_time_region, cpu);
 60
 61	/*
 62	 * paravirt_steal_clock() may be called before the CPU
 63	 * online notification callback runs. Until the callback
 64	 * has run we just return zero.
 65	 */
 66	rcu_read_lock();
 67	kaddr = rcu_dereference(reg->kaddr);
 68	if (!kaddr) {
 69		rcu_read_unlock();
 70		return 0;
 71	}
 72
 73	ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time));
 74	rcu_read_unlock();
 75	return ret;
 76}
 77
 78static int stolen_time_cpu_down_prepare(unsigned int cpu)
 79{
 80	struct pvclock_vcpu_stolen_time *kaddr = NULL;
 81	struct pv_time_stolen_time_region *reg;
 82
 83	reg = this_cpu_ptr(&stolen_time_region);
 84	if (!reg->kaddr)
 85		return 0;
 86
 87	kaddr = rcu_replace_pointer(reg->kaddr, NULL, true);
 88	synchronize_rcu();
 89	memunmap(kaddr);
 90
 91	return 0;
 92}
 93
 94static int stolen_time_cpu_online(unsigned int cpu)
 95{
 96	struct pvclock_vcpu_stolen_time *kaddr = NULL;
 97	struct pv_time_stolen_time_region *reg;
 98	struct arm_smccc_res res;
 99
100	reg = this_cpu_ptr(&stolen_time_region);
101
102	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
103
104	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
105		return -EINVAL;
106
107	kaddr = memremap(res.a0,
108			      sizeof(struct pvclock_vcpu_stolen_time),
109			      MEMREMAP_WB);
110
111	rcu_assign_pointer(reg->kaddr, kaddr);
112
113	if (!reg->kaddr) {
114		pr_warn("Failed to map stolen time data structure\n");
115		return -ENOMEM;
116	}
117
118	if (le32_to_cpu(kaddr->revision) != 0 ||
119	    le32_to_cpu(kaddr->attributes) != 0) {
120		pr_warn_once("Unexpected revision or attributes in stolen time data\n");
121		return -ENXIO;
122	}
123
124	return 0;
125}
126
127static int __init pv_time_init_stolen_time(void)
128{
129	int ret;
130
131	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
132				"hypervisor/arm/pvtime:online",
133				stolen_time_cpu_online,
134				stolen_time_cpu_down_prepare);
135	if (ret < 0)
136		return ret;
137	return 0;
138}
139
140static bool __init has_pv_steal_clock(void)
141{
142	struct arm_smccc_res res;
143
144	arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
145			     ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
146
147	if (res.a0 != SMCCC_RET_SUCCESS)
148		return false;
149
150	arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
151			     ARM_SMCCC_HV_PV_TIME_ST, &res);
152
153	return (res.a0 == SMCCC_RET_SUCCESS);
154}
155
156int __init pv_time_init(void)
157{
158	int ret;
159
160	if (!has_pv_steal_clock())
161		return 0;
162
163	ret = pv_time_init_stolen_time();
164	if (ret)
165		return ret;
166
167	static_call_update(pv_steal_clock, para_steal_clock);
168
169	static_key_slow_inc(&paravirt_steal_enabled);
170	if (steal_acc)
171		static_key_slow_inc(&paravirt_steal_rq_enabled);
172
173	pr_info("using stolen time PV\n");
174
175	return 0;
176}