arch/arm64/kernel/paravirt.c

   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
  27 struct static_key paravirt_steal_enabled;
  28 struct static_key paravirt_steal_rq_enabled;
  29
  30 static u64 native_steal_clock(int cpu)
  31 {
  32         return 0;
  33 }
  34
  35 DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
  36
  37 struct pv_time_stolen_time_region {
  38         struct pvclock_vcpu_stolen_time __rcu *kaddr;
  39 };
  40
  41 static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
  42
  43 static bool steal_acc = true;
  44 static int __init parse_no_stealacc(char *arg)
  45 {
  46         steal_acc = false;
  47         return 0;
  48 }
  49
  50 early_param("no-steal-acc", parse_no_stealacc);
  51
  52 /* return stolen time in ns by asking the hypervisor */
  53 static 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
  78 static 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
  94 static 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
 127 static 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
 140 static 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
 156 int __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 }