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 *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 pv_time_stolen_time_region *reg;
  56
  57         reg = per_cpu_ptr(&stolen_time_region, cpu);
  58
  59         /*
  60          * paravirt_steal_clock() may be called before the CPU
  61          * online notification callback runs. Until the callback
  62          * has run we just return zero.
  63          */
  64         if (!reg->kaddr)
  65                 return 0;
  66
  67         return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
  68 }
  69
  70 static int stolen_time_cpu_down_prepare(unsigned int cpu)
  71 {
  72         struct pv_time_stolen_time_region *reg;
  73
  74         reg = this_cpu_ptr(&stolen_time_region);
  75         if (!reg->kaddr)
  76                 return 0;
  77
  78         memunmap(reg->kaddr);
  79         memset(reg, 0, sizeof(*reg));
  80
  81         return 0;
  82 }
  83
  84 static int stolen_time_cpu_online(unsigned int cpu)
  85 {
  86         struct pv_time_stolen_time_region *reg;
  87         struct arm_smccc_res res;
  88
  89         reg = this_cpu_ptr(&stolen_time_region);
  90
  91         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
  92
  93         if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
  94                 return -EINVAL;
  95
  96         reg->kaddr = memremap(res.a0,
  97                               sizeof(struct pvclock_vcpu_stolen_time),
  98                               MEMREMAP_WB);
  99
 100         if (!reg->kaddr) {
 101                 pr_warn("Failed to map stolen time data structure\n");
 102                 return -ENOMEM;
 103         }
 104
 105         if (le32_to_cpu(reg->kaddr->revision) != 0 ||
 106             le32_to_cpu(reg->kaddr->attributes) != 0) {
 107                 pr_warn_once("Unexpected revision or attributes in stolen time data\n");
 108                 return -ENXIO;
 109         }
 110
 111         return 0;
 112 }
 113
 114 static int __init pv_time_init_stolen_time(void)
 115 {
 116         int ret;
 117
 118         ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
 119                                 "hypervisor/arm/pvtime:online",
 120                                 stolen_time_cpu_online,
 121                                 stolen_time_cpu_down_prepare);
 122         if (ret < 0)
 123                 return ret;
 124         return 0;
 125 }
 126
 127 static bool __init has_pv_steal_clock(void)
 128 {
 129         struct arm_smccc_res res;
 130
 131         /* To detect the presence of PV time support we require SMCCC 1.1+ */
 132         if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
 133                 return false;
 134
 135         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 136                              ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
 137
 138         if (res.a0 != SMCCC_RET_SUCCESS)
 139                 return false;
 140
 141         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
 142                              ARM_SMCCC_HV_PV_TIME_ST, &res);
 143
 144         return (res.a0 == SMCCC_RET_SUCCESS);
 145 }
 146
 147 int __init pv_time_init(void)
 148 {
 149         int ret;
 150
 151         if (!has_pv_steal_clock())
 152                 return 0;
 153
 154         ret = pv_time_init_stolen_time();
 155         if (ret)
 156                 return ret;
 157
 158         static_call_update(pv_steal_clock, para_steal_clock);
 159
 160         static_key_slow_inc(&paravirt_steal_enabled);
 161         if (steal_acc)
 162                 static_key_slow_inc(&paravirt_steal_rq_enabled);
 163
 164         pr_info("using stolen time PV\n");
 165
 166         return 0;
 167 }