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
  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;
  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 */
  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
  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
  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
 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
 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
 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(&paravirt_steal_enabled);
 169         if (steal_acc)
 170                 static_key_slow_inc(&paravirt_steal_rq_enabled);
 171
 172         pr_info("using stolen time PV\n");
 173
 174         return 0;
 175 }