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 28 #include <asm/x86_init.h> 29 #include <asm/reboot.h> 30 31 static int kvmclock = 1; 32 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; 33 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; 34 35 static int parse_no_kvmclock(char *arg) 36 { 37 kvmclock = 0; 38 return 0; 39 } 40 early_param("no-kvmclock", parse_no_kvmclock); 41 42 /* The hypervisor will put information about time periodically here */ 43 static struct pvclock_vsyscall_time_info *hv_clock; 44 static struct pvclock_wall_clock wall_clock; 45 46 /* 47 * The wallclock is the time of day when we booted. Since then, some time may 48 * have elapsed since the hypervisor wrote the data. So we try to account for 49 * that with system time 50 */ 51 static unsigned long kvm_get_wallclock(void) 52 { 53 struct pvclock_vcpu_time_info *vcpu_time; 54 struct timespec ts; 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 preempt_disable(); 64 cpu = smp_processor_id(); 65 66 vcpu_time = &hv_clock[cpu].pvti; 67 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); 68 69 preempt_enable(); 70 71 return ts.tv_sec; 72 } 73 74 static int kvm_set_wallclock(unsigned long now) 75 { 76 return -1; 77 } 78 79 static cycle_t kvm_clock_read(void) 80 { 81 struct pvclock_vcpu_time_info *src; 82 cycle_t ret; 83 int cpu; 84 85 preempt_disable_notrace(); 86 cpu = smp_processor_id(); 87 src = &hv_clock[cpu].pvti; 88 ret = pvclock_clocksource_read(src); 89 preempt_enable_notrace(); 90 return ret; 91 } 92 93 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 94 { 95 return kvm_clock_read(); 96 } 97 98 /* 99 * If we don't do that, there is the possibility that the guest 100 * will calibrate under heavy load - thus, getting a lower lpj - 101 * and execute the delays themselves without load. This is wrong, 102 * because no delay loop can finish beforehand. 103 * Any heuristics is subject to fail, because ultimately, a large 104 * poll of guests can be running and trouble each other. So we preset 105 * lpj here 106 */ 107 static unsigned long kvm_get_tsc_khz(void) 108 { 109 struct pvclock_vcpu_time_info *src; 110 int cpu; 111 unsigned long tsc_khz; 112 113 preempt_disable(); 114 cpu = smp_processor_id(); 115 src = &hv_clock[cpu].pvti; 116 tsc_khz = pvclock_tsc_khz(src); 117 preempt_enable(); 118 return tsc_khz; 119 } 120 121 static void kvm_get_preset_lpj(void) 122 { 123 unsigned long khz; 124 u64 lpj; 125 126 khz = kvm_get_tsc_khz(); 127 128 lpj = ((u64)khz * 1000); 129 do_div(lpj, HZ); 130 preset_lpj = lpj; 131 } 132 133 bool kvm_check_and_clear_guest_paused(void) 134 { 135 bool ret = false; 136 struct pvclock_vcpu_time_info *src; 137 int cpu = smp_processor_id(); 138 139 if (!hv_clock) 140 return ret; 141 142 src = &hv_clock[cpu].pvti; 143 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 144 src->flags &= ~PVCLOCK_GUEST_STOPPED; 145 ret = true; 146 } 147 148 return ret; 149 } 150 151 static struct clocksource kvm_clock = { 152 .name = "kvm-clock", 153 .read = kvm_clock_get_cycles, 154 .rating = 400, 155 .mask = CLOCKSOURCE_MASK(64), 156 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 157 }; 158 159 int kvm_register_clock(char *txt) 160 { 161 int cpu = smp_processor_id(); 162 int low, high, ret; 163 struct pvclock_vcpu_time_info *src = &hv_clock[cpu].pvti; 164 165 low = (int)__pa(src) | 1; 166 high = ((u64)__pa(src) >> 32); 167 ret = native_write_msr_safe(msr_kvm_system_time, low, high); 168 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 169 cpu, high, low, txt); 170 171 return ret; 172 } 173 174 static void kvm_save_sched_clock_state(void) 175 { 176 } 177 178 static void kvm_restore_sched_clock_state(void) 179 { 180 kvm_register_clock("primary cpu clock, resume"); 181 } 182 183 #ifdef CONFIG_X86_LOCAL_APIC 184 static void __cpuinit kvm_setup_secondary_clock(void) 185 { 186 /* 187 * Now that the first cpu already had this clocksource initialized, 188 * we shouldn't fail. 189 */ 190 WARN_ON(kvm_register_clock("secondary cpu clock")); 191 } 192 #endif 193 194 /* 195 * After the clock is registered, the host will keep writing to the 196 * registered memory location. If the guest happens to shutdown, this memory 197 * won't be valid. In cases like kexec, in which you install a new kernel, this 198 * means a random memory location will be kept being written. So before any 199 * kind of shutdown from our side, we unregister the clock by writting anything 200 * that does not have the 'enable' bit set in the msr 201 */ 202 #ifdef CONFIG_KEXEC 203 static void kvm_crash_shutdown(struct pt_regs *regs) 204 { 205 native_write_msr(msr_kvm_system_time, 0, 0); 206 kvm_disable_steal_time(); 207 native_machine_crash_shutdown(regs); 208 } 209 #endif 210 211 static void kvm_shutdown(void) 212 { 213 native_write_msr(msr_kvm_system_time, 0, 0); 214 kvm_disable_steal_time(); 215 native_machine_shutdown(); 216 } 217 218 void __init kvmclock_init(void) 219 { 220 unsigned long mem; 221 222 if (!kvm_para_available()) 223 return; 224 225 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 226 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 227 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 228 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 229 return; 230 231 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 232 msr_kvm_system_time, msr_kvm_wall_clock); 233 234 mem = memblock_alloc(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS, 235 PAGE_SIZE); 236 if (!mem) 237 return; 238 hv_clock = __va(mem); 239 240 if (kvm_register_clock("boot clock")) { 241 hv_clock = NULL; 242 memblock_free(mem, 243 sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 244 return; 245 } 246 pv_time_ops.sched_clock = kvm_clock_read; 247 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 248 x86_platform.get_wallclock = kvm_get_wallclock; 249 x86_platform.set_wallclock = kvm_set_wallclock; 250 #ifdef CONFIG_X86_LOCAL_APIC 251 x86_cpuinit.early_percpu_clock_init = 252 kvm_setup_secondary_clock; 253 #endif 254 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 255 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 256 machine_ops.shutdown = kvm_shutdown; 257 #ifdef CONFIG_KEXEC 258 machine_ops.crash_shutdown = kvm_crash_shutdown; 259 #endif 260 kvm_get_preset_lpj(); 261 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 262 pv_info.paravirt_enabled = 1; 263 pv_info.name = "KVM"; 264 265 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 266 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 267 } 268 269 int __init kvm_setup_vsyscall_timeinfo(void) 270 { 271 #ifdef CONFIG_X86_64 272 int cpu; 273 int ret; 274 u8 flags; 275 struct pvclock_vcpu_time_info *vcpu_time; 276 unsigned int size; 277 278 size = sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS; 279 280 preempt_disable(); 281 cpu = smp_processor_id(); 282 283 vcpu_time = &hv_clock[cpu].pvti; 284 flags = pvclock_read_flags(vcpu_time); 285 286 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) { 287 preempt_enable(); 288 return 1; 289 } 290 291 if ((ret = pvclock_init_vsyscall(hv_clock, size))) { 292 preempt_enable(); 293 return ret; 294 } 295 296 preempt_enable(); 297 298 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 299 #endif 300 return 0; 301 } 302