hw/i386/kvm/clock.c

   1 /*
   2  * QEMU KVM support, paravirtual clock device
   3  *
   4  * Copyright (C) 2011 Siemens AG
   5  *
   6  * Authors:
   7  *  Jan Kiszka        <jan.kiszka@siemens.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL version 2.
  10  * See the COPYING file in the top-level directory.
  11  *
  12  * Contributions after 2012-01-13 are licensed under the terms of the
  13  * GNU GPL, version 2 or (at your option) any later version.
  14  */
  15
  16 #include "qemu-common.h"
  17 #include "qemu/host-utils.h"
  18 #include "sysemu/sysemu.h"
  19 #include "sysemu/kvm.h"
  20 #include "sysemu/cpus.h"
  21 #include "hw/sysbus.h"
  22 #include "hw/kvm/clock.h"
  23
  24 #include <linux/kvm.h>
  25 #include <linux/kvm_para.h>
  26
  27 #define TYPE_KVM_CLOCK "kvmclock"
  28 #define KVM_CLOCK(obj) OBJECT_CHECK(KVMClockState, (obj), TYPE_KVM_CLOCK)
  29
  30 typedef struct KVMClockState {
  31     /*< private >*/
  32     SysBusDevice busdev;
  33     /*< public >*/
  34
  35     uint64_t clock;
  36     bool clock_valid;
  37 } KVMClockState;
  38
  39 struct pvclock_vcpu_time_info {
  40     uint32_t   version;
  41     uint32_t   pad0;
  42     uint64_t   tsc_timestamp;
  43     uint64_t   system_time;
  44     uint32_t   tsc_to_system_mul;
  45     int8_t     tsc_shift;
  46     uint8_t    flags;
  47     uint8_t    pad[2];
  48 } __attribute__((__packed__)); /* 32 bytes */
  49
  50 static uint64_t kvmclock_current_nsec(KVMClockState *s)
  51 {
  52     CPUState *cpu = first_cpu;
  53     CPUX86State *env = cpu->env_ptr;
  54     hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL;
  55     uint64_t migration_tsc = env->tsc;
  56     struct pvclock_vcpu_time_info time;
  57     uint64_t delta;
  58     uint64_t nsec_lo;
  59     uint64_t nsec_hi;
  60     uint64_t nsec;
  61
  62     if (!(env->system_time_msr & 1ULL)) {
  63         /* KVM clock not active */
  64         return 0;
  65     }
  66
  67     cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
  68
  69     assert(time.tsc_timestamp <= migration_tsc);
  70     delta = migration_tsc - time.tsc_timestamp;
  71     if (time.tsc_shift < 0) {
  72         delta >>= -time.tsc_shift;
  73     } else {
  74         delta <<= time.tsc_shift;
  75     }
  76
  77     mulu64(&nsec_lo, &nsec_hi, delta, time.tsc_to_system_mul);
  78     nsec = (nsec_lo >> 32) | (nsec_hi << 32);
  79     return nsec + time.system_time;
  80 }
  81
  82 static void kvmclock_vm_state_change(void *opaque, int running,
  83                                      RunState state)
  84 {
  85     KVMClockState *s = opaque;
  86     CPUState *cpu;
  87     int cap_clock_ctrl = kvm_check_extension(kvm_state, KVM_CAP_KVMCLOCK_CTRL);
  88     int ret;
  89
  90     if (running) {
  91         struct kvm_clock_data data = {};
  92         uint64_t time_at_migration = kvmclock_current_nsec(s);
  93
  94         s->clock_valid = false;
  95
  96         /* We can't rely on the migrated clock value, just discard it */
  97         if (time_at_migration) {
  98             s->clock = time_at_migration;
  99         }
 100
 101         data.clock = s->clock;
 102         ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);
 103         if (ret < 0) {
 104             fprintf(stderr, "KVM_SET_CLOCK failed: %s\n", strerror(ret));
 105             abort();
 106         }
 107
 108         if (!cap_clock_ctrl) {
 109             return;
 110         }
 111         CPU_FOREACH(cpu) {
 112             ret = kvm_vcpu_ioctl(cpu, KVM_KVMCLOCK_CTRL, 0);
 113             if (ret) {
 114                 if (ret != -EINVAL) {
 115                     fprintf(stderr, "%s: %s\n", __func__, strerror(-ret));
 116                 }
 117                 return;
 118             }
 119         }
 120     } else {
 121         struct kvm_clock_data data;
 122         int ret;
 123
 124         if (s->clock_valid) {
 125             return;
 126         }
 127
 128         cpu_synchronize_all_states();
 129         /* In theory, the cpu_synchronize_all_states() call above wouldn't
 130          * affect the rest of the code, as the VCPU state inside CPUState
 131          * is supposed to always match the VCPU state on the kernel side.
 132          *
 133          * In practice, calling cpu_synchronize_state() too soon will load the
 134          * kernel-side APIC state into X86CPU.apic_state too early, APIC state
 135          * won't be reloaded later because CPUState.vcpu_dirty==true, and
 136          * outdated APIC state may be migrated to another host.
 137          *
 138          * The real fix would be to make sure outdated APIC state is read
 139          * from the kernel again when necessary. While this is not fixed, we
 140          * need the cpu_clean_all_dirty() call below.
 141          */
 142         cpu_clean_all_dirty();
 143
 144         ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
 145         if (ret < 0) {
 146             fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));
 147             abort();
 148         }
 149         s->clock = data.clock;
 150
 151         /*
 152          * If the VM is stopped, declare the clock state valid to
 153          * avoid re-reading it on next vmsave (which would return
 154          * a different value). Will be reset when the VM is continued.
 155          */
 156         s->clock_valid = true;
 157     }
 158 }
 159
 160 static void kvmclock_realize(DeviceState *dev, Error **errp)
 161 {
 162     KVMClockState *s = KVM_CLOCK(dev);
 163
 164     qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s);
 165 }
 166
 167 static const VMStateDescription kvmclock_vmsd = {
 168     .name = "kvmclock",
 169     .version_id = 1,
 170     .minimum_version_id = 1,
 171     .fields = (VMStateField[]) {
 172         VMSTATE_UINT64(clock, KVMClockState),
 173         VMSTATE_END_OF_LIST()
 174     }
 175 };
 176
 177 static void kvmclock_class_init(ObjectClass *klass, void *data)
 178 {
 179     DeviceClass *dc = DEVICE_CLASS(klass);
 180
 181     dc->realize = kvmclock_realize;
 182     dc->vmsd = &kvmclock_vmsd;
 183 }
 184
 185 static const TypeInfo kvmclock_info = {
 186     .name          = TYPE_KVM_CLOCK,
 187     .parent        = TYPE_SYS_BUS_DEVICE,
 188     .instance_size = sizeof(KVMClockState),
 189     .class_init    = kvmclock_class_init,
 190 };
 191
 192 /* Note: Must be called after VCPU initialization. */
 193 void kvmclock_create(void)
 194 {
 195     X86CPU *cpu = X86_CPU(first_cpu);
 196
 197     if (kvm_enabled() &&
 198         cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) |
 199                                        (1ULL << KVM_FEATURE_CLOCKSOURCE2))) {
 200         sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL);
 201     }
 202 }
 203
 204 static void kvmclock_register_types(void)
 205 {
 206     type_register_static(&kvmclock_info);
 207 }
 208
 209 type_init(kvmclock_register_types)