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
22 #include <asm/paravirt.h>
23 #include <asm/pvclock-abi.h>
24 #include <asm/smp_plat.h>
25
26 struct static_key paravirt_steal_enabled;
27 struct static_key paravirt_steal_rq_enabled;
28
29 struct paravirt_patch_template pv_ops;
30 EXPORT_SYMBOL_GPL(pv_ops);
31
32 struct pv_time_stolen_time_region {
33 struct pvclock_vcpu_stolen_time __rcu *kaddr;
34 };
35
36 static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
37
38 static bool steal_acc = true;
parse_no_stealacc(char * arg)39 static int __init parse_no_stealacc(char *arg)
40 {
41 steal_acc = false;
42 return 0;
43 }
44
45 early_param("no-steal-acc", parse_no_stealacc);
46
47 /* return stolen time in ns by asking the hypervisor */
pv_steal_clock(int cpu)48 static u64 pv_steal_clock(int cpu)
49 {
50 struct pvclock_vcpu_stolen_time *kaddr = NULL;
51 struct pv_time_stolen_time_region *reg;
52 u64 ret = 0;
53
54 reg = per_cpu_ptr(&stolen_time_region, cpu);
55
56 /*
57 * paravirt_steal_clock() may be called before the CPU
58 * online notification callback runs. Until the callback
59 * has run we just return zero.
60 */
61 rcu_read_lock();
62 kaddr = rcu_dereference(reg->kaddr);
63 if (!kaddr) {
64 rcu_read_unlock();
65 return 0;
66 }
67
68 ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time));
69 rcu_read_unlock();
70 return ret;
71 }
72
stolen_time_cpu_down_prepare(unsigned int cpu)73 static int stolen_time_cpu_down_prepare(unsigned int cpu)
74 {
75 struct pvclock_vcpu_stolen_time *kaddr = NULL;
76 struct pv_time_stolen_time_region *reg;
77
78 reg = this_cpu_ptr(&stolen_time_region);
79 if (!reg->kaddr)
80 return 0;
81
82 kaddr = rcu_replace_pointer(reg->kaddr, NULL, true);
83 synchronize_rcu();
84 memunmap(kaddr);
85
86 return 0;
87 }
88
stolen_time_cpu_online(unsigned int cpu)89 static int stolen_time_cpu_online(unsigned int cpu)
90 {
91 struct pvclock_vcpu_stolen_time *kaddr = NULL;
92 struct pv_time_stolen_time_region *reg;
93 struct arm_smccc_res res;
94
95 reg = this_cpu_ptr(&stolen_time_region);
96
97 arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
98
99 if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
100 return -EINVAL;
101
102 kaddr = memremap(res.a0,
103 sizeof(struct pvclock_vcpu_stolen_time),
104 MEMREMAP_WB);
105
106 rcu_assign_pointer(reg->kaddr, kaddr);
107
108 if (!reg->kaddr) {
109 pr_warn("Failed to map stolen time data structure\n");
110 return -ENOMEM;
111 }
112
113 if (le32_to_cpu(kaddr->revision) != 0 ||
114 le32_to_cpu(kaddr->attributes) != 0) {
115 pr_warn_once("Unexpected revision or attributes in stolen time data\n");
116 return -ENXIO;
117 }
118
119 return 0;
120 }
121
pv_time_init_stolen_time(void)122 static int __init pv_time_init_stolen_time(void)
123 {
124 int ret;
125
126 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
127 "hypervisor/arm/pvtime:online",
128 stolen_time_cpu_online,
129 stolen_time_cpu_down_prepare);
130 if (ret < 0)
131 return ret;
132 return 0;
133 }
134
has_pv_steal_clock(void)135 static bool __init has_pv_steal_clock(void)
136 {
137 struct arm_smccc_res res;
138
139 /* To detect the presence of PV time support we require SMCCC 1.1+ */
140 if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
141 return false;
142
143 arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
144 ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
145
146 if (res.a0 != SMCCC_RET_SUCCESS)
147 return false;
148
149 arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
150 ARM_SMCCC_HV_PV_TIME_ST, &res);
151
152 return (res.a0 == SMCCC_RET_SUCCESS);
153 }
154
pv_time_init(void)155 int __init pv_time_init(void)
156 {
157 int ret;
158
159 if (!has_pv_steal_clock())
160 return 0;
161
162 ret = pv_time_init_stolen_time();
163 if (ret)
164 return ret;
165
166 pv_ops.time.steal_clock = pv_steal_clock;
167
168 static_key_slow_inc(¶virt_steal_enabled);
169 if (steal_acc)
170 static_key_slow_inc(¶virt_steal_rq_enabled);
171
172 pr_info("using stolen time PV\n");
173
174 return 0;
175 }
176