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 #include <linux/sched.h>
  28 #include <linux/sched/clock.h>
  29
  30 #include <asm/mem_encrypt.h>
  31 #include <asm/x86_init.h>
  32 #include <asm/reboot.h>
  33 #include <asm/kvmclock.h>
  34
  35 static int kvmclock __ro_after_init = 1;
  36 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
  37 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
  38 static u64 kvm_sched_clock_offset;
  39
  40 static int parse_no_kvmclock(char *arg)
  41 {
  42         kvmclock = 0;
  43         return 0;
  44 }
  45 early_param("no-kvmclock", parse_no_kvmclock);
  46
  47 /* The hypervisor will put information about time periodically here */
  48 static struct pvclock_vsyscall_time_info *hv_clock;
  49 static struct pvclock_wall_clock *wall_clock;
  50
  51 struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
  52 {
  53         return hv_clock;
  54 }
  55 EXPORT_SYMBOL_GPL(pvclock_pvti_cpu0_va);
  56
  57 /*
  58  * The wallclock is the time of day when we booted. Since then, some time may
  59  * have elapsed since the hypervisor wrote the data. So we try to account for
  60  * that with system time
  61  */
  62 static void kvm_get_wallclock(struct timespec *now)
  63 {
  64         struct pvclock_vcpu_time_info *vcpu_time;
  65         int low, high;
  66         int cpu;
  67
  68         low = (int)slow_virt_to_phys(wall_clock);
  69         high = ((u64)slow_virt_to_phys(wall_clock) >> 32);
  70
  71         native_write_msr(msr_kvm_wall_clock, low, high);
  72
  73         cpu = get_cpu();
  74
  75         vcpu_time = &hv_clock[cpu].pvti;
  76         pvclock_read_wallclock(wall_clock, vcpu_time, now);
  77
  78         put_cpu();
  79 }
  80
  81 static int kvm_set_wallclock(const struct timespec *now)
  82 {
  83         return -ENODEV;
  84 }
  85
  86 static u64 kvm_clock_read(void)
  87 {
  88         struct pvclock_vcpu_time_info *src;
  89         u64 ret;
  90         int cpu;
  91
  92         preempt_disable_notrace();
  93         cpu = smp_processor_id();
  94         src = &hv_clock[cpu].pvti;
  95         ret = pvclock_clocksource_read(src);
  96         preempt_enable_notrace();
  97         return ret;
  98 }
  99
 100 static u64 kvm_clock_get_cycles(struct clocksource *cs)
 101 {
 102         return kvm_clock_read();
 103 }
 104
 105 static u64 kvm_sched_clock_read(void)
 106 {
 107         return kvm_clock_read() - kvm_sched_clock_offset;
 108 }
 109
 110 static inline void kvm_sched_clock_init(bool stable)
 111 {
 112         if (!stable) {
 113                 pv_time_ops.sched_clock = kvm_clock_read;
 114                 clear_sched_clock_stable();
 115                 return;
 116         }
 117
 118         kvm_sched_clock_offset = kvm_clock_read();
 119         pv_time_ops.sched_clock = kvm_sched_clock_read;
 120
 121         printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
 122                         kvm_sched_clock_offset);
 123
 124         BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
 125                  sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
 126 }
 127
 128 /*
 129  * If we don't do that, there is the possibility that the guest
 130  * will calibrate under heavy load - thus, getting a lower lpj -
 131  * and execute the delays themselves without load. This is wrong,
 132  * because no delay loop can finish beforehand.
 133  * Any heuristics is subject to fail, because ultimately, a large
 134  * poll of guests can be running and trouble each other. So we preset
 135  * lpj here
 136  */
 137 static unsigned long kvm_get_tsc_khz(void)
 138 {
 139         struct pvclock_vcpu_time_info *src;
 140         int cpu;
 141         unsigned long tsc_khz;
 142
 143         cpu = get_cpu();
 144         src = &hv_clock[cpu].pvti;
 145         tsc_khz = pvclock_tsc_khz(src);
 146         put_cpu();
 147         return tsc_khz;
 148 }
 149
 150 static void kvm_get_preset_lpj(void)
 151 {
 152         unsigned long khz;
 153         u64 lpj;
 154
 155         khz = kvm_get_tsc_khz();
 156
 157         lpj = ((u64)khz * 1000);
 158         do_div(lpj, HZ);
 159         preset_lpj = lpj;
 160 }
 161
 162 bool kvm_check_and_clear_guest_paused(void)
 163 {
 164         bool ret = false;
 165         struct pvclock_vcpu_time_info *src;
 166         int cpu = smp_processor_id();
 167
 168         if (!hv_clock)
 169                 return ret;
 170
 171         src = &hv_clock[cpu].pvti;
 172         if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
 173                 src->flags &= ~PVCLOCK_GUEST_STOPPED;
 174                 pvclock_touch_watchdogs();
 175                 ret = true;
 176         }
 177
 178         return ret;
 179 }
 180
 181 struct clocksource kvm_clock = {
 182         .name = "kvm-clock",
 183         .read = kvm_clock_get_cycles,
 184         .rating = 400,
 185         .mask = CLOCKSOURCE_MASK(64),
 186         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 187 };
 188 EXPORT_SYMBOL_GPL(kvm_clock);
 189
 190 int kvm_register_clock(char *txt)
 191 {
 192         int cpu = smp_processor_id();
 193         int low, high, ret;
 194         struct pvclock_vcpu_time_info *src;
 195
 196         if (!hv_clock)
 197                 return 0;
 198
 199         src = &hv_clock[cpu].pvti;
 200         low = (int)slow_virt_to_phys(src) | 1;
 201         high = ((u64)slow_virt_to_phys(src) >> 32);
 202         ret = native_write_msr_safe(msr_kvm_system_time, low, high);
 203         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
 204                cpu, high, low, txt);
 205
 206         return ret;
 207 }
 208
 209 static void kvm_save_sched_clock_state(void)
 210 {
 211 }
 212
 213 static void kvm_restore_sched_clock_state(void)
 214 {
 215         kvm_register_clock("primary cpu clock, resume");
 216 }
 217
 218 #ifdef CONFIG_X86_LOCAL_APIC
 219 static void kvm_setup_secondary_clock(void)
 220 {
 221         /*
 222          * Now that the first cpu already had this clocksource initialized,
 223          * we shouldn't fail.
 224          */
 225         WARN_ON(kvm_register_clock("secondary cpu clock"));
 226 }
 227 #endif
 228
 229 /*
 230  * After the clock is registered, the host will keep writing to the
 231  * registered memory location. If the guest happens to shutdown, this memory
 232  * won't be valid. In cases like kexec, in which you install a new kernel, this
 233  * means a random memory location will be kept being written. So before any
 234  * kind of shutdown from our side, we unregister the clock by writing anything
 235  * that does not have the 'enable' bit set in the msr
 236  */
 237 #ifdef CONFIG_KEXEC_CORE
 238 static void kvm_crash_shutdown(struct pt_regs *regs)
 239 {
 240         native_write_msr(msr_kvm_system_time, 0, 0);
 241         kvm_disable_steal_time();
 242         native_machine_crash_shutdown(regs);
 243 }
 244 #endif
 245
 246 static void kvm_shutdown(void)
 247 {
 248         native_write_msr(msr_kvm_system_time, 0, 0);
 249         kvm_disable_steal_time();
 250         native_machine_shutdown();
 251 }
 252
 253 static phys_addr_t __init kvm_memblock_alloc(phys_addr_t size,
 254                                              phys_addr_t align)
 255 {
 256         phys_addr_t mem;
 257
 258         mem = memblock_alloc(size, align);
 259         if (!mem)
 260                 return 0;
 261
 262         if (sev_active()) {
 263                 if (early_set_memory_decrypted((unsigned long)__va(mem), size))
 264                         goto e_free;
 265         }
 266
 267         return mem;
 268 e_free:
 269         memblock_free(mem, size);
 270         return 0;
 271 }
 272
 273 static void __init kvm_memblock_free(phys_addr_t addr, phys_addr_t size)
 274 {
 275         if (sev_active())
 276                 early_set_memory_encrypted((unsigned long)__va(addr), size);
 277
 278         memblock_free(addr, size);
 279 }
 280
 281 void __init kvmclock_init(void)
 282 {
 283         struct pvclock_vcpu_time_info *vcpu_time;
 284         unsigned long mem, mem_wall_clock;
 285         int size, cpu, wall_clock_size;
 286         u8 flags;
 287
 288         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
 289
 290         if (!kvm_para_available())
 291                 return;
 292
 293         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 294                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 295                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 296         } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
 297                 return;
 298
 299         wall_clock_size = PAGE_ALIGN(sizeof(struct pvclock_wall_clock));
 300         mem_wall_clock = kvm_memblock_alloc(wall_clock_size, PAGE_SIZE);
 301         if (!mem_wall_clock)
 302                 return;
 303
 304         wall_clock = __va(mem_wall_clock);
 305         memset(wall_clock, 0, wall_clock_size);
 306
 307         mem = kvm_memblock_alloc(size, PAGE_SIZE);
 308         if (!mem) {
 309                 kvm_memblock_free(mem_wall_clock, wall_clock_size);
 310                 wall_clock = NULL;
 311                 return;
 312         }
 313
 314         hv_clock = __va(mem);
 315         memset(hv_clock, 0, size);
 316
 317         if (kvm_register_clock("primary cpu clock")) {
 318                 hv_clock = NULL;
 319                 kvm_memblock_free(mem, size);
 320                 kvm_memblock_free(mem_wall_clock, wall_clock_size);
 321                 wall_clock = NULL;
 322                 return;
 323         }
 324
 325         printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
 326                 msr_kvm_system_time, msr_kvm_wall_clock);
 327
 328         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 329                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 330
 331         cpu = get_cpu();
 332         vcpu_time = &hv_clock[cpu].pvti;
 333         flags = pvclock_read_flags(vcpu_time);
 334
 335         kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
 336         put_cpu();
 337
 338         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 339         x86_platform.calibrate_cpu = kvm_get_tsc_khz;
 340         x86_platform.get_wallclock = kvm_get_wallclock;
 341         x86_platform.set_wallclock = kvm_set_wallclock;
 342 #ifdef CONFIG_X86_LOCAL_APIC
 343         x86_cpuinit.early_percpu_clock_init =
 344                 kvm_setup_secondary_clock;
 345 #endif
 346         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 347         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
 348         machine_ops.shutdown  = kvm_shutdown;
 349 #ifdef CONFIG_KEXEC_CORE
 350         machine_ops.crash_shutdown  = kvm_crash_shutdown;
 351 #endif
 352         kvm_get_preset_lpj();
 353         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 354         pv_info.name = "KVM";
 355 }
 356
 357 int __init kvm_setup_vsyscall_timeinfo(void)
 358 {
 359 #ifdef CONFIG_X86_64
 360         int cpu;
 361         u8 flags;
 362         struct pvclock_vcpu_time_info *vcpu_time;
 363         unsigned int size;
 364
 365         if (!hv_clock)
 366                 return 0;
 367
 368         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
 369
 370         cpu = get_cpu();
 371
 372         vcpu_time = &hv_clock[cpu].pvti;
 373         flags = pvclock_read_flags(vcpu_time);
 374
 375         if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
 376                 put_cpu();
 377                 return 1;
 378         }
 379
 380         put_cpu();
 381
 382         kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
 383 #endif
 384         return 0;
 385 }