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 29 #include <asm/x86_init.h> 30 #include <asm/reboot.h> 31 32 static int kvmclock __ro_after_init = 1; 33 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; 34 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; 35 static cycle_t kvm_sched_clock_offset; 36 37 static int parse_no_kvmclock(char *arg) 38 { 39 kvmclock = 0; 40 return 0; 41 } 42 early_param("no-kvmclock", parse_no_kvmclock); 43 44 /* The hypervisor will put information about time periodically here */ 45 static struct pvclock_vsyscall_time_info *hv_clock; 46 static struct pvclock_wall_clock wall_clock; 47 48 struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void) 49 { 50 return hv_clock; 51 } 52 53 /* 54 * The wallclock is the time of day when we booted. Since then, some time may 55 * have elapsed since the hypervisor wrote the data. So we try to account for 56 * that with system time 57 */ 58 static void kvm_get_wallclock(struct timespec *now) 59 { 60 struct pvclock_vcpu_time_info *vcpu_time; 61 int low, high; 62 int cpu; 63 64 low = (int)__pa_symbol(&wall_clock); 65 high = ((u64)__pa_symbol(&wall_clock) >> 32); 66 67 native_write_msr(msr_kvm_wall_clock, low, high); 68 69 cpu = get_cpu(); 70 71 vcpu_time = &hv_clock[cpu].pvti; 72 pvclock_read_wallclock(&wall_clock, vcpu_time, now); 73 74 put_cpu(); 75 } 76 77 static int kvm_set_wallclock(const struct timespec *now) 78 { 79 return -1; 80 } 81 82 static cycle_t kvm_clock_read(void) 83 { 84 struct pvclock_vcpu_time_info *src; 85 cycle_t ret; 86 int cpu; 87 88 preempt_disable_notrace(); 89 cpu = smp_processor_id(); 90 src = &hv_clock[cpu].pvti; 91 ret = pvclock_clocksource_read(src); 92 preempt_enable_notrace(); 93 return ret; 94 } 95 96 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 97 { 98 return kvm_clock_read(); 99 } 100 101 static cycle_t kvm_sched_clock_read(void) 102 { 103 return kvm_clock_read() - kvm_sched_clock_offset; 104 } 105 106 static inline void kvm_sched_clock_init(bool stable) 107 { 108 if (!stable) { 109 pv_time_ops.sched_clock = kvm_clock_read; 110 return; 111 } 112 113 kvm_sched_clock_offset = kvm_clock_read(); 114 pv_time_ops.sched_clock = kvm_sched_clock_read; 115 set_sched_clock_stable(); 116 117 printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n", 118 kvm_sched_clock_offset); 119 120 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 121 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 122 } 123 124 /* 125 * If we don't do that, there is the possibility that the guest 126 * will calibrate under heavy load - thus, getting a lower lpj - 127 * and execute the delays themselves without load. This is wrong, 128 * because no delay loop can finish beforehand. 129 * Any heuristics is subject to fail, because ultimately, a large 130 * poll of guests can be running and trouble each other. So we preset 131 * lpj here 132 */ 133 static unsigned long kvm_get_tsc_khz(void) 134 { 135 struct pvclock_vcpu_time_info *src; 136 int cpu; 137 unsigned long tsc_khz; 138 139 cpu = get_cpu(); 140 src = &hv_clock[cpu].pvti; 141 tsc_khz = pvclock_tsc_khz(src); 142 put_cpu(); 143 return tsc_khz; 144 } 145 146 static void kvm_get_preset_lpj(void) 147 { 148 unsigned long khz; 149 u64 lpj; 150 151 khz = kvm_get_tsc_khz(); 152 153 lpj = ((u64)khz * 1000); 154 do_div(lpj, HZ); 155 preset_lpj = lpj; 156 } 157 158 bool kvm_check_and_clear_guest_paused(void) 159 { 160 bool ret = false; 161 struct pvclock_vcpu_time_info *src; 162 int cpu = smp_processor_id(); 163 164 if (!hv_clock) 165 return ret; 166 167 src = &hv_clock[cpu].pvti; 168 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 169 src->flags &= ~PVCLOCK_GUEST_STOPPED; 170 pvclock_touch_watchdogs(); 171 ret = true; 172 } 173 174 return ret; 175 } 176 177 static struct clocksource kvm_clock = { 178 .name = "kvm-clock", 179 .read = kvm_clock_get_cycles, 180 .rating = 400, 181 .mask = CLOCKSOURCE_MASK(64), 182 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 183 }; 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 void __init kvmclock_init(void) 249 { 250 struct pvclock_vcpu_time_info *vcpu_time; 251 unsigned long mem; 252 int size, cpu; 253 u8 flags; 254 255 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 256 257 if (!kvm_para_available()) 258 return; 259 260 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 261 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 262 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 263 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 264 return; 265 266 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 267 msr_kvm_system_time, msr_kvm_wall_clock); 268 269 mem = memblock_alloc(size, PAGE_SIZE); 270 if (!mem) 271 return; 272 hv_clock = __va(mem); 273 memset(hv_clock, 0, size); 274 275 if (kvm_register_clock("primary cpu clock")) { 276 hv_clock = NULL; 277 memblock_free(mem, size); 278 return; 279 } 280 281 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 282 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 283 284 cpu = get_cpu(); 285 vcpu_time = &hv_clock[cpu].pvti; 286 flags = pvclock_read_flags(vcpu_time); 287 288 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 289 put_cpu(); 290 291 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 292 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 293 x86_platform.get_wallclock = kvm_get_wallclock; 294 x86_platform.set_wallclock = kvm_set_wallclock; 295 #ifdef CONFIG_X86_LOCAL_APIC 296 x86_cpuinit.early_percpu_clock_init = 297 kvm_setup_secondary_clock; 298 #endif 299 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 300 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 301 machine_ops.shutdown = kvm_shutdown; 302 #ifdef CONFIG_KEXEC_CORE 303 machine_ops.crash_shutdown = kvm_crash_shutdown; 304 #endif 305 kvm_get_preset_lpj(); 306 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 307 pv_info.name = "KVM"; 308 } 309 310 int __init kvm_setup_vsyscall_timeinfo(void) 311 { 312 #ifdef CONFIG_X86_64 313 int cpu; 314 u8 flags; 315 struct pvclock_vcpu_time_info *vcpu_time; 316 unsigned int size; 317 318 if (!hv_clock) 319 return 0; 320 321 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 322 323 cpu = get_cpu(); 324 325 vcpu_time = &hv_clock[cpu].pvti; 326 flags = pvclock_read_flags(vcpu_time); 327 328 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) { 329 put_cpu(); 330 return 1; 331 } 332 333 put_cpu(); 334 335 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 336 #endif 337 return 0; 338 } 339