arch/x86/kernel/kvmclock.c

   1 /*  KVM paravirtual clock driver. A clocksource implementation
   2     Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (at your option) any later version.
   8
   9     This program is distributed in the hope that it will be useful,
  10     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12     GNU General Public License for more details.
  13
  14     You should have received a copy of the GNU General Public License
  15     along with this program; if not, write to the Free Software
  16     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17 */
  18
  19 #include <linux/clocksource.h>
  20 #include <linux/kvm_para.h>
  21 #include <asm/pvclock.h>
  22 #include <asm/msr.h>
  23 #include <asm/apic.h>
  24 #include <linux/percpu.h>
  25 #include <linux/hardirq.h>
  26
  27 #include <asm/x86_init.h>
  28 #include <asm/reboot.h>
  29
  30 static int kvmclock = 1;
  31 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
  32 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
  33
  34 static int parse_no_kvmclock(char *arg)
  35 {
  36         kvmclock = 0;
  37         return 0;
  38 }
  39 early_param("no-kvmclock", parse_no_kvmclock);
  40
  41 /* The hypervisor will put information about time periodically here */
  42 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
  43 static struct pvclock_wall_clock wall_clock;
  44
  45 /*
  46  * The wallclock is the time of day when we booted. Since then, some time may
  47  * have elapsed since the hypervisor wrote the data. So we try to account for
  48  * that with system time
  49  */
  50 static unsigned long kvm_get_wallclock(void)
  51 {
  52         struct pvclock_vcpu_time_info *vcpu_time;
  53         struct timespec ts;
  54         int low, high;
  55
  56         low = (int)__pa_symbol(&wall_clock);
  57         high = ((u64)__pa_symbol(&wall_clock) >> 32);
  58
  59         native_write_msr(msr_kvm_wall_clock, low, high);
  60
  61         vcpu_time = &get_cpu_var(hv_clock);
  62         pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
  63         put_cpu_var(hv_clock);
  64
  65         return ts.tv_sec;
  66 }
  67
  68 static int kvm_set_wallclock(unsigned long now)
  69 {
  70         return -1;
  71 }
  72
  73 static cycle_t kvm_clock_read(void)
  74 {
  75         struct pvclock_vcpu_time_info *src;
  76         cycle_t ret;
  77
  78         preempt_disable_notrace();
  79         src = &__get_cpu_var(hv_clock);
  80         ret = pvclock_clocksource_read(src);
  81         preempt_enable_notrace();
  82         return ret;
  83 }
  84
  85 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
  86 {
  87         return kvm_clock_read();
  88 }
  89
  90 /*
  91  * If we don't do that, there is the possibility that the guest
  92  * will calibrate under heavy load - thus, getting a lower lpj -
  93  * and execute the delays themselves without load. This is wrong,
  94  * because no delay loop can finish beforehand.
  95  * Any heuristics is subject to fail, because ultimately, a large
  96  * poll of guests can be running and trouble each other. So we preset
  97  * lpj here
  98  */
  99 static unsigned long kvm_get_tsc_khz(void)
 100 {
 101         struct pvclock_vcpu_time_info *src;
 102         src = &per_cpu(hv_clock, 0);
 103         return pvclock_tsc_khz(src);
 104 }
 105
 106 static void kvm_get_preset_lpj(void)
 107 {
 108         unsigned long khz;
 109         u64 lpj;
 110
 111         khz = kvm_get_tsc_khz();
 112
 113         lpj = ((u64)khz * 1000);
 114         do_div(lpj, HZ);
 115         preset_lpj = lpj;
 116 }
 117
 118 bool kvm_check_and_clear_guest_paused(void)
 119 {
 120         bool ret = false;
 121         struct pvclock_vcpu_time_info *src;
 122
 123         src = &__get_cpu_var(hv_clock);
 124         if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
 125                 __this_cpu_and(hv_clock.flags, ~PVCLOCK_GUEST_STOPPED);
 126                 ret = true;
 127         }
 128
 129         return ret;
 130 }
 131
 132 static struct clocksource kvm_clock = {
 133         .name = "kvm-clock",
 134         .read = kvm_clock_get_cycles,
 135         .rating = 400,
 136         .mask = CLOCKSOURCE_MASK(64),
 137         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 138 };
 139
 140 int kvm_register_clock(char *txt)
 141 {
 142         int cpu = smp_processor_id();
 143         int low, high, ret;
 144
 145         low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
 146         high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
 147         ret = native_write_msr_safe(msr_kvm_system_time, low, high);
 148         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
 149                cpu, high, low, txt);
 150
 151         return ret;
 152 }
 153
 154 static void kvm_save_sched_clock_state(void)
 155 {
 156 }
 157
 158 static void kvm_restore_sched_clock_state(void)
 159 {
 160         kvm_register_clock("primary cpu clock, resume");
 161 }
 162
 163 #ifdef CONFIG_X86_LOCAL_APIC
 164 static void __cpuinit kvm_setup_secondary_clock(void)
 165 {
 166         /*
 167          * Now that the first cpu already had this clocksource initialized,
 168          * we shouldn't fail.
 169          */
 170         WARN_ON(kvm_register_clock("secondary cpu clock"));
 171 }
 172 #endif
 173
 174 /*
 175  * After the clock is registered, the host will keep writing to the
 176  * registered memory location. If the guest happens to shutdown, this memory
 177  * won't be valid. In cases like kexec, in which you install a new kernel, this
 178  * means a random memory location will be kept being written. So before any
 179  * kind of shutdown from our side, we unregister the clock by writting anything
 180  * that does not have the 'enable' bit set in the msr
 181  */
 182 #ifdef CONFIG_KEXEC
 183 static void kvm_crash_shutdown(struct pt_regs *regs)
 184 {
 185         native_write_msr(msr_kvm_system_time, 0, 0);
 186         kvm_disable_steal_time();
 187         native_machine_crash_shutdown(regs);
 188 }
 189 #endif
 190
 191 static void kvm_shutdown(void)
 192 {
 193         native_write_msr(msr_kvm_system_time, 0, 0);
 194         kvm_disable_steal_time();
 195         native_machine_shutdown();
 196 }
 197
 198 void __init kvmclock_init(void)
 199 {
 200         if (!kvm_para_available())
 201                 return;
 202
 203         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 204                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 205                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 206         } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
 207                 return;
 208
 209         printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
 210                 msr_kvm_system_time, msr_kvm_wall_clock);
 211
 212         if (kvm_register_clock("boot clock"))
 213                 return;
 214         pv_time_ops.sched_clock = kvm_clock_read;
 215         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 216         x86_platform.get_wallclock = kvm_get_wallclock;
 217         x86_platform.set_wallclock = kvm_set_wallclock;
 218 #ifdef CONFIG_X86_LOCAL_APIC
 219         x86_cpuinit.early_percpu_clock_init =
 220                 kvm_setup_secondary_clock;
 221 #endif
 222         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 223         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
 224         machine_ops.shutdown  = kvm_shutdown;
 225 #ifdef CONFIG_KEXEC
 226         machine_ops.crash_shutdown  = kvm_crash_shutdown;
 227 #endif
 228         kvm_get_preset_lpj();
 229         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 230         pv_info.paravirt_enabled = 1;
 231         pv_info.name = "KVM";
 232
 233         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 234                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 235 }