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