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 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 __cpuinit 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 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 unsigned long mem; 222 int size; 223 224 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 225 226 if (!kvm_para_available()) 227 return; 228 229 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 230 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 231 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 232 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 233 return; 234 235 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 236 msr_kvm_system_time, msr_kvm_wall_clock); 237 238 mem = memblock_alloc(size, PAGE_SIZE); 239 if (!mem) 240 return; 241 hv_clock = __va(mem); 242 memset(hv_clock, 0, size); 243 244 if (kvm_register_clock("boot clock")) { 245 hv_clock = NULL; 246 memblock_free(mem, size); 247 return; 248 } 249 pv_time_ops.sched_clock = kvm_clock_read; 250 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 251 x86_platform.get_wallclock = kvm_get_wallclock; 252 x86_platform.set_wallclock = kvm_set_wallclock; 253 #ifdef CONFIG_X86_LOCAL_APIC 254 x86_cpuinit.early_percpu_clock_init = 255 kvm_setup_secondary_clock; 256 #endif 257 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 258 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 259 machine_ops.shutdown = kvm_shutdown; 260 #ifdef CONFIG_KEXEC 261 machine_ops.crash_shutdown = kvm_crash_shutdown; 262 #endif 263 kvm_get_preset_lpj(); 264 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 265 pv_info.paravirt_enabled = 1; 266 pv_info.name = "KVM"; 267 268 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 269 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 270 } 271 272 int __init kvm_setup_vsyscall_timeinfo(void) 273 { 274 #ifdef CONFIG_X86_64 275 int cpu; 276 int ret; 277 u8 flags; 278 struct pvclock_vcpu_time_info *vcpu_time; 279 unsigned int size; 280 281 if (!hv_clock) 282 return 0; 283 284 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 285 286 preempt_disable(); 287 cpu = smp_processor_id(); 288 289 vcpu_time = &hv_clock[cpu].pvti; 290 flags = pvclock_read_flags(vcpu_time); 291 292 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) { 293 preempt_enable(); 294 return 1; 295 } 296 297 if ((ret = pvclock_init_vsyscall(hv_clock, size))) { 298 preempt_enable(); 299 return ret; 300 } 301 302 preempt_enable(); 303 304 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 305 #endif 306 return 0; 307 } 308