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
  26 #include <asm/x86_init.h>
  27 #include <asm/reboot.h>
  28
  29 #define KVM_SCALE 22
  30
  31 static int kvmclock = 1;
  32 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
  33 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
  34
  35 static int parse_no_kvmclock(char *arg)
  36 {
  37         kvmclock = 0;
  38         return 0;
  39 }
  40 early_param("no-kvmclock", parse_no_kvmclock);
  41
  42 /* The hypervisor will put information about time periodically here */
  43 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
  44 static struct pvclock_wall_clock wall_clock;
  45
  46 /*
  47  * The wallclock is the time of day when we booted. Since then, some time may
  48  * have elapsed since the hypervisor wrote the data. So we try to account for
  49  * that with system time
  50  */
  51 static unsigned long kvm_get_wallclock(void)
  52 {
  53         struct pvclock_vcpu_time_info *vcpu_time;
  54         struct timespec ts;
  55         int low, high;
  56
  57         low = (int)__pa_symbol(&wall_clock);
  58         high = ((u64)__pa_symbol(&wall_clock) >> 32);
  59
  60         native_write_msr(msr_kvm_wall_clock, low, high);
  61
  62         vcpu_time = &get_cpu_var(hv_clock);
  63         pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
  64         put_cpu_var(hv_clock);
  65
  66         return ts.tv_sec;
  67 }
  68
  69 static int kvm_set_wallclock(unsigned long now)
  70 {
  71         return -1;
  72 }
  73
  74 static cycle_t kvm_clock_read(void)
  75 {
  76         struct pvclock_vcpu_time_info *src;
  77         cycle_t ret;
  78
  79         src = &get_cpu_var(hv_clock);
  80         ret = pvclock_clocksource_read(src);
  81         put_cpu_var(hv_clock);
  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 static struct clocksource kvm_clock = {
 119         .name = "kvm-clock",
 120         .read = kvm_clock_get_cycles,
 121         .rating = 400,
 122         .mask = CLOCKSOURCE_MASK(64),
 123         .mult = 1 << KVM_SCALE,
 124         .shift = KVM_SCALE,
 125         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 126 };
 127
 128 int kvm_register_clock(char *txt)
 129 {
 130         int cpu = smp_processor_id();
 131         int low, high, ret;
 132
 133         low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
 134         high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
 135         ret = native_write_msr_safe(msr_kvm_system_time, low, high);
 136         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
 137                cpu, high, low, txt);
 138
 139         return ret;
 140 }
 141
 142 #ifdef CONFIG_X86_LOCAL_APIC
 143 static void __cpuinit kvm_setup_secondary_clock(void)
 144 {
 145         /*
 146          * Now that the first cpu already had this clocksource initialized,
 147          * we shouldn't fail.
 148          */
 149         WARN_ON(kvm_register_clock("secondary cpu clock"));
 150         /* ok, done with our trickery, call native */
 151         setup_secondary_APIC_clock();
 152 }
 153 #endif
 154
 155 /*
 156  * After the clock is registered, the host will keep writing to the
 157  * registered memory location. If the guest happens to shutdown, this memory
 158  * won't be valid. In cases like kexec, in which you install a new kernel, this
 159  * means a random memory location will be kept being written. So before any
 160  * kind of shutdown from our side, we unregister the clock by writting anything
 161  * that does not have the 'enable' bit set in the msr
 162  */
 163 #ifdef CONFIG_KEXEC
 164 static void kvm_crash_shutdown(struct pt_regs *regs)
 165 {
 166         native_write_msr(msr_kvm_system_time, 0, 0);
 167         native_machine_crash_shutdown(regs);
 168 }
 169 #endif
 170
 171 static void kvm_shutdown(void)
 172 {
 173         native_write_msr(msr_kvm_system_time, 0, 0);
 174         native_machine_shutdown();
 175 }
 176
 177 void __init kvmclock_init(void)
 178 {
 179         if (!kvm_para_available())
 180                 return;
 181
 182         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 183                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 184                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 185         } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
 186                 return;
 187
 188         printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
 189                 msr_kvm_system_time, msr_kvm_wall_clock);
 190
 191         if (kvm_register_clock("boot clock"))
 192                 return;
 193         pv_time_ops.sched_clock = kvm_clock_read;
 194         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 195         x86_platform.get_wallclock = kvm_get_wallclock;
 196         x86_platform.set_wallclock = kvm_set_wallclock;
 197 #ifdef CONFIG_X86_LOCAL_APIC
 198         x86_cpuinit.setup_percpu_clockev =
 199                 kvm_setup_secondary_clock;
 200 #endif
 201         machine_ops.shutdown  = kvm_shutdown;
 202 #ifdef CONFIG_KEXEC
 203         machine_ops.crash_shutdown  = kvm_crash_shutdown;
 204 #endif
 205         kvm_get_preset_lpj();
 206         clocksource_register(&kvm_clock);
 207         pv_info.paravirt_enabled = 1;
 208         pv_info.name = "KVM";
 209
 210         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 211                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 212 }