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 void kvm_get_wallclock(struct timespec *now) 52 { 53 struct pvclock_vcpu_time_info *vcpu_time; 54 int low, high; 55 int cpu; 56 57 low = (int)__pa_symbol(&wall_clock); 58 high = ((u64)__pa_symbol(&wall_clock) >> 32); 59 60 native_write_msr(msr_kvm_wall_clock, low, high); 61 62 preempt_disable(); 63 cpu = smp_processor_id(); 64 65 vcpu_time = &hv_clock[cpu].pvti; 66 pvclock_read_wallclock(&wall_clock, vcpu_time, now); 67 68 preempt_enable(); 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 preempt_disable(); 111 cpu = smp_processor_id(); 112 src = &hv_clock[cpu].pvti; 113 tsc_khz = pvclock_tsc_khz(src); 114 preempt_enable(); 115 return tsc_khz; 116 } 117 118 static void kvm_get_preset_lpj(void) 119 { 120 unsigned long khz; 121 u64 lpj; 122 123 khz = kvm_get_tsc_khz(); 124 125 lpj = ((u64)khz * 1000); 126 do_div(lpj, HZ); 127 preset_lpj = lpj; 128 } 129 130 bool kvm_check_and_clear_guest_paused(void) 131 { 132 bool ret = false; 133 struct pvclock_vcpu_time_info *src; 134 int cpu = smp_processor_id(); 135 136 if (!hv_clock) 137 return ret; 138 139 src = &hv_clock[cpu].pvti; 140 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 141 src->flags &= ~PVCLOCK_GUEST_STOPPED; 142 pvclock_touch_watchdogs(); 143 ret = true; 144 } 145 146 return ret; 147 } 148 149 static struct clocksource kvm_clock = { 150 .name = "kvm-clock", 151 .read = kvm_clock_get_cycles, 152 .rating = 400, 153 .mask = CLOCKSOURCE_MASK(64), 154 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 155 }; 156 157 int kvm_register_clock(char *txt) 158 { 159 int cpu = smp_processor_id(); 160 int low, high, ret; 161 struct pvclock_vcpu_time_info *src; 162 163 if (!hv_clock) 164 return 0; 165 166 src = &hv_clock[cpu].pvti; 167 low = (int)slow_virt_to_phys(src) | 1; 168 high = ((u64)slow_virt_to_phys(src) >> 32); 169 ret = native_write_msr_safe(msr_kvm_system_time, low, high); 170 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 171 cpu, high, low, txt); 172 173 return ret; 174 } 175 176 static void kvm_save_sched_clock_state(void) 177 { 178 } 179 180 static void kvm_restore_sched_clock_state(void) 181 { 182 kvm_register_clock("primary cpu clock, resume"); 183 } 184 185 #ifdef CONFIG_X86_LOCAL_APIC 186 static void kvm_setup_secondary_clock(void) 187 { 188 /* 189 * Now that the first cpu already had this clocksource initialized, 190 * we shouldn't fail. 191 */ 192 WARN_ON(kvm_register_clock("secondary cpu clock")); 193 } 194 #endif 195 196 /* 197 * After the clock is registered, the host will keep writing to the 198 * registered memory location. If the guest happens to shutdown, this memory 199 * won't be valid. In cases like kexec, in which you install a new kernel, this 200 * means a random memory location will be kept being written. So before any 201 * kind of shutdown from our side, we unregister the clock by writting anything 202 * that does not have the 'enable' bit set in the msr 203 */ 204 #ifdef CONFIG_KEXEC 205 static void kvm_crash_shutdown(struct pt_regs *regs) 206 { 207 native_write_msr(msr_kvm_system_time, 0, 0); 208 kvm_disable_steal_time(); 209 native_machine_crash_shutdown(regs); 210 } 211 #endif 212 213 static void kvm_shutdown(void) 214 { 215 native_write_msr(msr_kvm_system_time, 0, 0); 216 kvm_disable_steal_time(); 217 native_machine_shutdown(); 218 } 219 220 void __init kvmclock_init(void) 221 { 222 unsigned long mem; 223 int size; 224 225 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 226 227 if (!kvm_para_available()) 228 return; 229 230 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 231 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 232 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 233 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 234 return; 235 236 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 237 msr_kvm_system_time, msr_kvm_wall_clock); 238 239 mem = memblock_alloc(size, PAGE_SIZE); 240 if (!mem) 241 return; 242 hv_clock = __va(mem); 243 memset(hv_clock, 0, size); 244 245 if (kvm_register_clock("primary cpu clock")) { 246 hv_clock = NULL; 247 memblock_free(mem, size); 248 return; 249 } 250 pv_time_ops.sched_clock = kvm_clock_read; 251 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 252 x86_platform.get_wallclock = kvm_get_wallclock; 253 x86_platform.set_wallclock = kvm_set_wallclock; 254 #ifdef CONFIG_X86_LOCAL_APIC 255 x86_cpuinit.early_percpu_clock_init = 256 kvm_setup_secondary_clock; 257 #endif 258 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 259 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 260 machine_ops.shutdown = kvm_shutdown; 261 #ifdef CONFIG_KEXEC 262 machine_ops.crash_shutdown = kvm_crash_shutdown; 263 #endif 264 kvm_get_preset_lpj(); 265 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 266 pv_info.paravirt_enabled = 1; 267 pv_info.name = "KVM"; 268 269 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 270 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 271 } 272 273 int __init kvm_setup_vsyscall_timeinfo(void) 274 { 275 #ifdef CONFIG_X86_64 276 int cpu; 277 int ret; 278 u8 flags; 279 struct pvclock_vcpu_time_info *vcpu_time; 280 unsigned int size; 281 282 if (!hv_clock) 283 return 0; 284 285 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 286 287 preempt_disable(); 288 cpu = smp_processor_id(); 289 290 vcpu_time = &hv_clock[cpu].pvti; 291 flags = pvclock_read_flags(vcpu_time); 292 293 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) { 294 preempt_enable(); 295 return 1; 296 } 297 298 if ((ret = pvclock_init_vsyscall(hv_clock, size))) { 299 preempt_enable(); 300 return ret; 301 } 302 303 preempt_enable(); 304 305 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 306 #endif 307 return 0; 308 } 309