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 } 386