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 #include <linux/memblock.h>
  27
  28 #include <asm/x86_init.h>
  29 #include <asm/reboot.h>
  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 struct pvclock_vsyscall_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 void kvm_get_wallclock(struct timespec *now)
  52 {
  53         struct pvclock_vcpu_time_info *vcpu_time;
  54         int low, high;
  55         int cpu;
  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         cpu = get_cpu();
  63
  64         vcpu_time = &hv_clock[cpu].pvti;
  65         pvclock_read_wallclock(&wall_clock, vcpu_time, now);
  66
  67         put_cpu();
  68 }
  69
  70 static int kvm_set_wallclock(const struct timespec *now)
  71 {
  72         return -1;
  73 }
  74
  75 static cycle_t kvm_clock_read(void)
  76 {
  77         struct pvclock_vcpu_time_info *src;
  78         cycle_t ret;
  79         int cpu;
  80
  81         preempt_disable_notrace();
  82         cpu = smp_processor_id();
  83         src = &hv_clock[cpu].pvti;
  84         ret = pvclock_clocksource_read(src);
  85         preempt_enable_notrace();
  86         return ret;
  87 }
  88
  89 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
  90 {
  91         return kvm_clock_read();
  92 }
  93
  94 /*
  95  * If we don't do that, there is the possibility that the guest
  96  * will calibrate under heavy load - thus, getting a lower lpj -
  97  * and execute the delays themselves without load. This is wrong,
  98  * because no delay loop can finish beforehand.
  99  * Any heuristics is subject to fail, because ultimately, a large
 100  * poll of guests can be running and trouble each other. So we preset
 101  * lpj here
 102  */
 103 static unsigned long kvm_get_tsc_khz(void)
 104 {
 105         struct pvclock_vcpu_time_info *src;
 106         int cpu;
 107         unsigned long tsc_khz;
 108
 109         cpu = get_cpu();
 110         src = &hv_clock[cpu].pvti;
 111         tsc_khz = pvclock_tsc_khz(src);
 112         put_cpu();
 113         return tsc_khz;
 114 }
 115
 116 static void kvm_get_preset_lpj(void)
 117 {
 118         unsigned long khz;
 119         u64 lpj;
 120
 121         khz = kvm_get_tsc_khz();
 122
 123         lpj = ((u64)khz * 1000);
 124         do_div(lpj, HZ);
 125         preset_lpj = lpj;
 126 }
 127
 128 bool kvm_check_and_clear_guest_paused(void)
 129 {
 130         bool ret = false;
 131         struct pvclock_vcpu_time_info *src;
 132         int cpu = smp_processor_id();
 133
 134         if (!hv_clock)
 135                 return ret;
 136
 137         src = &hv_clock[cpu].pvti;
 138         if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
 139                 src->flags &= ~PVCLOCK_GUEST_STOPPED;
 140                 pvclock_touch_watchdogs();
 141                 ret = true;
 142         }
 143
 144         return ret;
 145 }
 146
 147 static struct clocksource kvm_clock = {
 148         .name = "kvm-clock",
 149         .read = kvm_clock_get_cycles,
 150         .rating = 400,
 151         .mask = CLOCKSOURCE_MASK(64),
 152         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 153 };
 154
 155 int kvm_register_clock(char *txt)
 156 {
 157         int cpu = smp_processor_id();
 158         int low, high, ret;
 159         struct pvclock_vcpu_time_info *src;
 160
 161         if (!hv_clock)
 162                 return 0;
 163
 164         src = &hv_clock[cpu].pvti;
 165         low = (int)slow_virt_to_phys(src) | 1;
 166         high = ((u64)slow_virt_to_phys(src) >> 32);
 167         ret = native_write_msr_safe(msr_kvm_system_time, low, high);
 168         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
 169                cpu, high, low, txt);
 170
 171         return ret;
 172 }
 173
 174 static void kvm_save_sched_clock_state(void)
 175 {
 176 }
 177
 178 static void kvm_restore_sched_clock_state(void)
 179 {
 180         kvm_register_clock("primary cpu clock, resume");
 181 }
 182
 183 #ifdef CONFIG_X86_LOCAL_APIC
 184 static void kvm_setup_secondary_clock(void)
 185 {
 186         /*
 187          * Now that the first cpu already had this clocksource initialized,
 188          * we shouldn't fail.
 189          */
 190         WARN_ON(kvm_register_clock("secondary cpu clock"));
 191 }
 192 #endif
 193
 194 /*
 195  * After the clock is registered, the host will keep writing to the
 196  * registered memory location. If the guest happens to shutdown, this memory
 197  * won't be valid. In cases like kexec, in which you install a new kernel, this
 198  * means a random memory location will be kept being written. So before any
 199  * kind of shutdown from our side, we unregister the clock by writting anything
 200  * that does not have the 'enable' bit set in the msr
 201  */
 202 #ifdef CONFIG_KEXEC
 203 static void kvm_crash_shutdown(struct pt_regs *regs)
 204 {
 205         native_write_msr(msr_kvm_system_time, 0, 0);
 206         kvm_disable_steal_time();
 207         native_machine_crash_shutdown(regs);
 208 }
 209 #endif
 210
 211 static void kvm_shutdown(void)
 212 {
 213         native_write_msr(msr_kvm_system_time, 0, 0);
 214         kvm_disable_steal_time();
 215         native_machine_shutdown();
 216 }
 217
 218 void __init kvmclock_init(void)
 219 {
 220         unsigned long mem;
 221         int size;
 222
 223         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
 224
 225         if (!kvm_para_available())
 226                 return;
 227
 228         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 229                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 230                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 231         } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
 232                 return;
 233
 234         printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
 235                 msr_kvm_system_time, msr_kvm_wall_clock);
 236
 237         mem = memblock_alloc(size, PAGE_SIZE);
 238         if (!mem)
 239                 return;
 240         hv_clock = __va(mem);
 241         memset(hv_clock, 0, size);
 242
 243         if (kvm_register_clock("primary cpu clock")) {
 244                 hv_clock = NULL;
 245                 memblock_free(mem, size);
 246                 return;
 247         }
 248         pv_time_ops.sched_clock = kvm_clock_read;
 249         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 250         x86_platform.get_wallclock = kvm_get_wallclock;
 251         x86_platform.set_wallclock = kvm_set_wallclock;
 252 #ifdef CONFIG_X86_LOCAL_APIC
 253         x86_cpuinit.early_percpu_clock_init =
 254                 kvm_setup_secondary_clock;
 255 #endif
 256         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 257         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
 258         machine_ops.shutdown  = kvm_shutdown;
 259 #ifdef CONFIG_KEXEC
 260         machine_ops.crash_shutdown  = kvm_crash_shutdown;
 261 #endif
 262         kvm_get_preset_lpj();
 263         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 264         pv_info.name = "KVM";
 265
 266         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 267                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 268 }
 269
 270 int __init kvm_setup_vsyscall_timeinfo(void)
 271 {
 272 #ifdef CONFIG_X86_64
 273         int cpu;
 274         int ret;
 275         u8 flags;
 276         struct pvclock_vcpu_time_info *vcpu_time;
 277         unsigned int size;
 278
 279         if (!hv_clock)
 280                 return 0;
 281
 282         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
 283
 284         cpu = get_cpu();
 285
 286         vcpu_time = &hv_clock[cpu].pvti;
 287         flags = pvclock_read_flags(vcpu_time);
 288
 289         if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
 290                 put_cpu();
 291                 return 1;
 292         }
 293
 294         if ((ret = pvclock_init_vsyscall(hv_clock, size))) {
 295                 put_cpu();
 296                 return ret;
 297         }
 298
 299         put_cpu();
 300
 301         kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
 302 #endif
 303         return 0;
 304 }