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 <asm/reboot.h>
  26
  27 #define KVM_SCALE 22
  28
  29 static int kvmclock = 1;
  30
  31 static int parse_no_kvmclock(char *arg)
  32 {
  33         kvmclock = 0;
  34         return 0;
  35 }
  36 early_param("no-kvmclock", parse_no_kvmclock);
  37
  38 /* The hypervisor will put information about time periodically here */
  39 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
  40 static struct pvclock_wall_clock wall_clock;
  41
  42 /*
  43  * The wallclock is the time of day when we booted. Since then, some time may
  44  * have elapsed since the hypervisor wrote the data. So we try to account for
  45  * that with system time
  46  */
  47 static unsigned long kvm_get_wallclock(void)
  48 {
  49         struct pvclock_vcpu_time_info *vcpu_time;
  50         struct timespec ts;
  51         int low, high;
  52
  53         low = (int)__pa_symbol(&wall_clock);
  54         high = ((u64)__pa_symbol(&wall_clock) >> 32);
  55         native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
  56
  57         vcpu_time = &get_cpu_var(hv_clock);
  58         pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
  59         put_cpu_var(hv_clock);
  60
  61         return ts.tv_sec;
  62 }
  63
  64 static int kvm_set_wallclock(unsigned long now)
  65 {
  66         return -1;
  67 }
  68
  69 static cycle_t kvm_clock_read(void)
  70 {
  71         struct pvclock_vcpu_time_info *src;
  72         cycle_t ret;
  73
  74         src = &get_cpu_var(hv_clock);
  75         ret = pvclock_clocksource_read(src);
  76         put_cpu_var(hv_clock);
  77         return ret;
  78 }
  79
  80 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
  81 {
  82         return kvm_clock_read();
  83 }
  84
  85 /*
  86  * If we don't do that, there is the possibility that the guest
  87  * will calibrate under heavy load - thus, getting a lower lpj -
  88  * and execute the delays themselves without load. This is wrong,
  89  * because no delay loop can finish beforehand.
  90  * Any heuristics is subject to fail, because ultimately, a large
  91  * poll of guests can be running and trouble each other. So we preset
  92  * lpj here
  93  */
  94 static unsigned long kvm_get_tsc_khz(void)
  95 {
  96         struct pvclock_vcpu_time_info *src;
  97         src = &per_cpu(hv_clock, 0);
  98         return pvclock_tsc_khz(src);
  99 }
 100
 101 static void kvm_get_preset_lpj(void)
 102 {
 103         unsigned long khz;
 104         u64 lpj;
 105
 106         khz = kvm_get_tsc_khz();
 107
 108         lpj = ((u64)khz * 1000);
 109         do_div(lpj, HZ);
 110         preset_lpj = lpj;
 111 }
 112
 113 static struct clocksource kvm_clock = {
 114         .name = "kvm-clock",
 115         .read = kvm_clock_get_cycles,
 116         .rating = 400,
 117         .mask = CLOCKSOURCE_MASK(64),
 118         .mult = 1 << KVM_SCALE,
 119         .shift = KVM_SCALE,
 120         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 121 };
 122
 123 static int kvm_register_clock(char *txt)
 124 {
 125         int cpu = smp_processor_id();
 126         int low, high;
 127         low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
 128         high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
 129         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
 130                cpu, high, low, txt);
 131         return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
 132 }
 133
 134 #ifdef CONFIG_X86_LOCAL_APIC
 135 static void __cpuinit kvm_setup_secondary_clock(void)
 136 {
 137         /*
 138          * Now that the first cpu already had this clocksource initialized,
 139          * we shouldn't fail.
 140          */
 141         WARN_ON(kvm_register_clock("secondary cpu clock"));
 142         /* ok, done with our trickery, call native */
 143         setup_secondary_APIC_clock();
 144 }
 145 #endif
 146
 147 #ifdef CONFIG_SMP
 148 static void __init kvm_smp_prepare_boot_cpu(void)
 149 {
 150         WARN_ON(kvm_register_clock("primary cpu clock"));
 151         native_smp_prepare_boot_cpu();
 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_safe(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_safe(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_CLOCKSOURCE)) {
 183                 if (kvm_register_clock("boot clock"))
 184                         return;
 185                 pv_time_ops.get_wallclock = kvm_get_wallclock;
 186                 pv_time_ops.set_wallclock = kvm_set_wallclock;
 187                 pv_time_ops.sched_clock = kvm_clock_read;
 188                 pv_time_ops.get_tsc_khz = kvm_get_tsc_khz;
 189 #ifdef CONFIG_X86_LOCAL_APIC
 190                 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
 191 #endif
 192 #ifdef CONFIG_SMP
 193                 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 194 #endif
 195                 machine_ops.shutdown  = kvm_shutdown;
 196 #ifdef CONFIG_KEXEC
 197                 machine_ops.crash_shutdown  = kvm_crash_shutdown;
 198 #endif
 199                 kvm_get_preset_lpj();
 200                 clocksource_register(&kvm_clock);
 201                 pv_info.paravirt_enabled = 1;
 202                 pv_info.name = "KVM";
 203         }
 204 }