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/arch_hooks.h>
  23 #include <asm/msr.h>
  24 #include <asm/apic.h>
  25 #include <linux/percpu.h>
  26 #include <asm/reboot.h>
  27
  28 #define KVM_SCALE 22
  29
  30 static int kvmclock = 1;
  31
  32 static int parse_no_kvmclock(char *arg)
  33 {
  34         kvmclock = 0;
  35         return 0;
  36 }
  37 early_param("no-kvmclock", parse_no_kvmclock);
  38
  39 /* The hypervisor will put information about time periodically here */
  40 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
  41 static struct pvclock_wall_clock wall_clock;
  42
  43 /*
  44  * The wallclock is the time of day when we booted. Since then, some time may
  45  * have elapsed since the hypervisor wrote the data. So we try to account for
  46  * that with system time
  47  */
  48 static unsigned long kvm_get_wallclock(void)
  49 {
  50         struct pvclock_vcpu_time_info *vcpu_time;
  51         struct timespec ts;
  52         int low, high;
  53
  54         low = (int)__pa(&wall_clock);
  55         high = ((u64)__pa(&wall_clock) >> 32);
  56         native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
  57
  58         vcpu_time = &get_cpu_var(hv_clock);
  59         pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
  60         put_cpu_var(hv_clock);
  61
  62         return ts.tv_sec;
  63 }
  64
  65 static int kvm_set_wallclock(unsigned long now)
  66 {
  67         return -1;
  68 }
  69
  70 static cycle_t kvm_clock_read(void)
  71 {
  72         struct pvclock_vcpu_time_info *src;
  73         cycle_t ret;
  74
  75         src = &get_cpu_var(hv_clock);
  76         ret = pvclock_clocksource_read(src);
  77         put_cpu_var(hv_clock);
  78         return ret;
  79 }
  80
  81 static struct clocksource kvm_clock = {
  82         .name = "kvm-clock",
  83         .read = kvm_clock_read,
  84         .rating = 400,
  85         .mask = CLOCKSOURCE_MASK(64),
  86         .mult = 1 << KVM_SCALE,
  87         .shift = KVM_SCALE,
  88         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
  89 };
  90
  91 static int kvm_register_clock(char *txt)
  92 {
  93         int cpu = smp_processor_id();
  94         int low, high;
  95         low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
  96         high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
  97         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
  98                cpu, high, low, txt);
  99         return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
 100 }
 101
 102 #ifdef CONFIG_X86_LOCAL_APIC
 103 static void kvm_setup_secondary_clock(void)
 104 {
 105         /*
 106          * Now that the first cpu already had this clocksource initialized,
 107          * we shouldn't fail.
 108          */
 109         WARN_ON(kvm_register_clock("secondary cpu clock"));
 110         /* ok, done with our trickery, call native */
 111         setup_secondary_APIC_clock();
 112 }
 113 #endif
 114
 115 #ifdef CONFIG_SMP
 116 void __init kvm_smp_prepare_boot_cpu(void)
 117 {
 118         WARN_ON(kvm_register_clock("primary cpu clock"));
 119         native_smp_prepare_boot_cpu();
 120 }
 121 #endif
 122
 123 /*
 124  * After the clock is registered, the host will keep writing to the
 125  * registered memory location. If the guest happens to shutdown, this memory
 126  * won't be valid. In cases like kexec, in which you install a new kernel, this
 127  * means a random memory location will be kept being written. So before any
 128  * kind of shutdown from our side, we unregister the clock by writting anything
 129  * that does not have the 'enable' bit set in the msr
 130  */
 131 #ifdef CONFIG_KEXEC
 132 static void kvm_crash_shutdown(struct pt_regs *regs)
 133 {
 134         native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
 135         native_machine_crash_shutdown(regs);
 136 }
 137 #endif
 138
 139 static void kvm_shutdown(void)
 140 {
 141         native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
 142         native_machine_shutdown();
 143 }
 144
 145 void __init kvmclock_init(void)
 146 {
 147         if (!kvm_para_available())
 148                 return;
 149
 150         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
 151                 if (kvm_register_clock("boot clock"))
 152                         return;
 153                 pv_time_ops.get_wallclock = kvm_get_wallclock;
 154                 pv_time_ops.set_wallclock = kvm_set_wallclock;
 155                 pv_time_ops.sched_clock = kvm_clock_read;
 156 #ifdef CONFIG_X86_LOCAL_APIC
 157                 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
 158 #endif
 159 #ifdef CONFIG_SMP
 160                 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
 161 #endif
 162                 machine_ops.shutdown  = kvm_shutdown;
 163 #ifdef CONFIG_KEXEC
 164                 machine_ops.crash_shutdown  = kvm_crash_shutdown;
 165 #endif
 166                 clocksource_register(&kvm_clock);
 167         }
 168 }