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 /* 52 * The wallclock is the time of day when we booted. Since then, some time may 53 * have elapsed since the hypervisor wrote the data. So we try to account for 54 * that with system time 55 */ 56 static void kvm_get_wallclock(struct timespec64 *now) 57 { 58 struct pvclock_vcpu_time_info *vcpu_time; 59 int low, high; 60 int cpu; 61 62 low = (int)slow_virt_to_phys(wall_clock); 63 high = ((u64)slow_virt_to_phys(wall_clock) >> 32); 64 65 native_write_msr(msr_kvm_wall_clock, low, high); 66 67 cpu = get_cpu(); 68 69 vcpu_time = &hv_clock[cpu].pvti; 70 pvclock_read_wallclock(wall_clock, vcpu_time, now); 71 72 put_cpu(); 73 } 74 75 static int kvm_set_wallclock(const struct timespec64 *now) 76 { 77 return -ENODEV; 78 } 79 80 static u64 kvm_clock_read(void) 81 { 82 struct pvclock_vcpu_time_info *src; 83 u64 ret; 84 int cpu; 85 86 preempt_disable_notrace(); 87 cpu = smp_processor_id(); 88 src = &hv_clock[cpu].pvti; 89 ret = pvclock_clocksource_read(src); 90 preempt_enable_notrace(); 91 return ret; 92 } 93 94 static u64 kvm_clock_get_cycles(struct clocksource *cs) 95 { 96 return kvm_clock_read(); 97 } 98 99 static u64 kvm_sched_clock_read(void) 100 { 101 return kvm_clock_read() - kvm_sched_clock_offset; 102 } 103 104 static inline void kvm_sched_clock_init(bool stable) 105 { 106 if (!stable) { 107 pv_time_ops.sched_clock = kvm_clock_read; 108 clear_sched_clock_stable(); 109 return; 110 } 111 112 kvm_sched_clock_offset = kvm_clock_read(); 113 pv_time_ops.sched_clock = kvm_sched_clock_read; 114 115 printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n", 116 kvm_sched_clock_offset); 117 118 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 119 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 120 } 121 122 /* 123 * If we don't do that, there is the possibility that the guest 124 * will calibrate under heavy load - thus, getting a lower lpj - 125 * and execute the delays themselves without load. This is wrong, 126 * because no delay loop can finish beforehand. 127 * Any heuristics is subject to fail, because ultimately, a large 128 * poll of guests can be running and trouble each other. So we preset 129 * lpj here 130 */ 131 static unsigned long kvm_get_tsc_khz(void) 132 { 133 struct pvclock_vcpu_time_info *src; 134 int cpu; 135 unsigned long tsc_khz; 136 137 cpu = get_cpu(); 138 src = &hv_clock[cpu].pvti; 139 tsc_khz = pvclock_tsc_khz(src); 140 put_cpu(); 141 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); 142 return tsc_khz; 143 } 144 145 static void kvm_get_preset_lpj(void) 146 { 147 unsigned long khz; 148 u64 lpj; 149 150 khz = kvm_get_tsc_khz(); 151 152 lpj = ((u64)khz * 1000); 153 do_div(lpj, HZ); 154 preset_lpj = lpj; 155 } 156 157 bool kvm_check_and_clear_guest_paused(void) 158 { 159 bool ret = false; 160 struct pvclock_vcpu_time_info *src; 161 int cpu = smp_processor_id(); 162 163 if (!hv_clock) 164 return ret; 165 166 src = &hv_clock[cpu].pvti; 167 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 168 src->flags &= ~PVCLOCK_GUEST_STOPPED; 169 pvclock_touch_watchdogs(); 170 ret = true; 171 } 172 173 return ret; 174 } 175 176 struct clocksource kvm_clock = { 177 .name = "kvm-clock", 178 .read = kvm_clock_get_cycles, 179 .rating = 400, 180 .mask = CLOCKSOURCE_MASK(64), 181 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 182 }; 183 EXPORT_SYMBOL_GPL(kvm_clock); 184 185 int kvm_register_clock(char *txt) 186 { 187 int cpu = smp_processor_id(); 188 int low, high, ret; 189 struct pvclock_vcpu_time_info *src; 190 191 if (!hv_clock) 192 return 0; 193 194 src = &hv_clock[cpu].pvti; 195 low = (int)slow_virt_to_phys(src) | 1; 196 high = ((u64)slow_virt_to_phys(src) >> 32); 197 ret = native_write_msr_safe(msr_kvm_system_time, low, high); 198 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 199 cpu, high, low, txt); 200 201 return ret; 202 } 203 204 static void kvm_save_sched_clock_state(void) 205 { 206 } 207 208 static void kvm_restore_sched_clock_state(void) 209 { 210 kvm_register_clock("primary cpu clock, resume"); 211 } 212 213 #ifdef CONFIG_X86_LOCAL_APIC 214 static void kvm_setup_secondary_clock(void) 215 { 216 /* 217 * Now that the first cpu already had this clocksource initialized, 218 * we shouldn't fail. 219 */ 220 WARN_ON(kvm_register_clock("secondary cpu clock")); 221 } 222 #endif 223 224 /* 225 * After the clock is registered, the host will keep writing to the 226 * registered memory location. If the guest happens to shutdown, this memory 227 * won't be valid. In cases like kexec, in which you install a new kernel, this 228 * means a random memory location will be kept being written. So before any 229 * kind of shutdown from our side, we unregister the clock by writing anything 230 * that does not have the 'enable' bit set in the msr 231 */ 232 #ifdef CONFIG_KEXEC_CORE 233 static void kvm_crash_shutdown(struct pt_regs *regs) 234 { 235 native_write_msr(msr_kvm_system_time, 0, 0); 236 kvm_disable_steal_time(); 237 native_machine_crash_shutdown(regs); 238 } 239 #endif 240 241 static void kvm_shutdown(void) 242 { 243 native_write_msr(msr_kvm_system_time, 0, 0); 244 kvm_disable_steal_time(); 245 native_machine_shutdown(); 246 } 247 248 static phys_addr_t __init kvm_memblock_alloc(phys_addr_t size, 249 phys_addr_t align) 250 { 251 phys_addr_t mem; 252 253 mem = memblock_alloc(size, align); 254 if (!mem) 255 return 0; 256 257 if (sev_active()) { 258 if (early_set_memory_decrypted((unsigned long)__va(mem), size)) 259 goto e_free; 260 } 261 262 return mem; 263 e_free: 264 memblock_free(mem, size); 265 return 0; 266 } 267 268 static void __init kvm_memblock_free(phys_addr_t addr, phys_addr_t size) 269 { 270 if (sev_active()) 271 early_set_memory_encrypted((unsigned long)__va(addr), size); 272 273 memblock_free(addr, size); 274 } 275 276 void __init kvmclock_init(void) 277 { 278 struct pvclock_vcpu_time_info *vcpu_time; 279 unsigned long mem, mem_wall_clock; 280 int size, cpu, wall_clock_size; 281 u8 flags; 282 283 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 284 285 if (!kvm_para_available()) 286 return; 287 288 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 289 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 290 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 291 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 292 return; 293 294 wall_clock_size = PAGE_ALIGN(sizeof(struct pvclock_wall_clock)); 295 mem_wall_clock = kvm_memblock_alloc(wall_clock_size, PAGE_SIZE); 296 if (!mem_wall_clock) 297 return; 298 299 wall_clock = __va(mem_wall_clock); 300 memset(wall_clock, 0, wall_clock_size); 301 302 mem = kvm_memblock_alloc(size, PAGE_SIZE); 303 if (!mem) { 304 kvm_memblock_free(mem_wall_clock, wall_clock_size); 305 wall_clock = NULL; 306 return; 307 } 308 309 hv_clock = __va(mem); 310 memset(hv_clock, 0, size); 311 312 if (kvm_register_clock("primary cpu clock")) { 313 hv_clock = NULL; 314 kvm_memblock_free(mem, size); 315 kvm_memblock_free(mem_wall_clock, wall_clock_size); 316 wall_clock = NULL; 317 return; 318 } 319 320 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 321 msr_kvm_system_time, msr_kvm_wall_clock); 322 323 pvclock_set_pvti_cpu0_va(hv_clock); 324 325 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 326 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 327 328 cpu = get_cpu(); 329 vcpu_time = &hv_clock[cpu].pvti; 330 flags = pvclock_read_flags(vcpu_time); 331 332 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 333 put_cpu(); 334 335 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 336 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 337 x86_platform.get_wallclock = kvm_get_wallclock; 338 x86_platform.set_wallclock = kvm_set_wallclock; 339 #ifdef CONFIG_X86_LOCAL_APIC 340 x86_cpuinit.early_percpu_clock_init = 341 kvm_setup_secondary_clock; 342 #endif 343 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 344 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 345 machine_ops.shutdown = kvm_shutdown; 346 #ifdef CONFIG_KEXEC_CORE 347 machine_ops.crash_shutdown = kvm_crash_shutdown; 348 #endif 349 kvm_get_preset_lpj(); 350 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 351 pv_info.name = "KVM"; 352 } 353 354 int __init kvm_setup_vsyscall_timeinfo(void) 355 { 356 #ifdef CONFIG_X86_64 357 int cpu; 358 u8 flags; 359 struct pvclock_vcpu_time_info *vcpu_time; 360 unsigned int size; 361 362 if (!hv_clock) 363 return 0; 364 365 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 366 367 cpu = get_cpu(); 368 369 vcpu_time = &hv_clock[cpu].pvti; 370 flags = pvclock_read_flags(vcpu_time); 371 372 put_cpu(); 373 374 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) 375 return 1; 376 377 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 378 #endif 379 return 0; 380 } 381