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