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 *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 pv_time_stolen_time_region *reg;
  51
  52         reg = per_cpu_ptr(&stolen_time_region, cpu);
  53         if (!reg->kaddr) {
  54                 pr_warn_once("stolen time enabled but not configured for cpu %d\n",
  55                              cpu);
  56                 return 0;
  57         }
  58
  59         return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
  60 }
  61
  62 static int stolen_time_dying_cpu(unsigned int cpu)
  63 {
  64         struct pv_time_stolen_time_region *reg;
  65
  66         reg = this_cpu_ptr(&stolen_time_region);
  67         if (!reg->kaddr)
  68                 return 0;
  69
  70         memunmap(reg->kaddr);
  71         memset(reg, 0, sizeof(*reg));
  72
  73         return 0;
  74 }
  75
  76 static int init_stolen_time_cpu(unsigned int cpu)
  77 {
  78         struct pv_time_stolen_time_region *reg;
  79         struct arm_smccc_res res;
  80
  81         reg = this_cpu_ptr(&stolen_time_region);
  82
  83         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
  84
  85         if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
  86                 return -EINVAL;
  87
  88         reg->kaddr = memremap(res.a0,
  89                               sizeof(struct pvclock_vcpu_stolen_time),
  90                               MEMREMAP_WB);
  91
  92         if (!reg->kaddr) {
  93                 pr_warn("Failed to map stolen time data structure\n");
  94                 return -ENOMEM;
  95         }
  96
  97         if (le32_to_cpu(reg->kaddr->revision) != 0 ||
  98             le32_to_cpu(reg->kaddr->attributes) != 0) {
  99                 pr_warn_once("Unexpected revision or attributes in stolen time data\n");
 100                 return -ENXIO;
 101         }
 102
 103         return 0;
 104 }
 105
 106 static int pv_time_init_stolen_time(void)
 107 {
 108         int ret;
 109
 110         ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
 111                                 "hypervisor/arm/pvtime:starting",
 112                                 init_stolen_time_cpu, stolen_time_dying_cpu);
 113         if (ret < 0)
 114                 return ret;
 115         return 0;
 116 }
 117
 118 static bool has_pv_steal_clock(void)
 119 {
 120         struct arm_smccc_res res;
 121
 122         /* To detect the presence of PV time support we require SMCCC 1.1+ */
 123         if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
 124                 return false;
 125
 126         arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
 127                              ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
 128
 129         if (res.a0 != SMCCC_RET_SUCCESS)
 130                 return false;
 131
 132         arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
 133                              ARM_SMCCC_HV_PV_TIME_ST, &res);
 134
 135         return (res.a0 == SMCCC_RET_SUCCESS);
 136 }
 137
 138 int __init pv_time_init(void)
 139 {
 140         int ret;
 141
 142         if (!has_pv_steal_clock())
 143                 return 0;
 144
 145         ret = pv_time_init_stolen_time();
 146         if (ret)
 147                 return ret;
 148
 149         pv_ops.time.steal_clock = pv_steal_clock;
 150
 151         static_key_slow_inc(&paravirt_steal_enabled);
 152         if (steal_acc)
 153                 static_key_slow_inc(&paravirt_steal_rq_enabled);
 154
 155         pr_info("using stolen time PV\n");
 156
 157         return 0;
 158 }