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