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 cpu = get_cpu(); 63 64 vcpu_time = &hv_clock[cpu].pvti; 65 pvclock_read_wallclock(&wall_clock, vcpu_time, now); 66 67 put_cpu(); 68 } 69 70 static int kvm_set_wallclock(const struct timespec *now) 71 { 72 return -1; 73 } 74 75 static cycle_t kvm_clock_read(void) 76 { 77 struct pvclock_vcpu_time_info *src; 78 cycle_t ret; 79 int cpu; 80 81 preempt_disable_notrace(); 82 cpu = smp_processor_id(); 83 src = &hv_clock[cpu].pvti; 84 ret = pvclock_clocksource_read(src); 85 preempt_enable_notrace(); 86 return ret; 87 } 88 89 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 90 { 91 return kvm_clock_read(); 92 } 93 94 /* 95 * If we don't do that, there is the possibility that the guest 96 * will calibrate under heavy load - thus, getting a lower lpj - 97 * and execute the delays themselves without load. This is wrong, 98 * because no delay loop can finish beforehand. 99 * Any heuristics is subject to fail, because ultimately, a large 100 * poll of guests can be running and trouble each other. So we preset 101 * lpj here 102 */ 103 static unsigned long kvm_get_tsc_khz(void) 104 { 105 struct pvclock_vcpu_time_info *src; 106 int cpu; 107 unsigned long tsc_khz; 108 109 cpu = get_cpu(); 110 src = &hv_clock[cpu].pvti; 111 tsc_khz = pvclock_tsc_khz(src); 112 put_cpu(); 113 return tsc_khz; 114 } 115 116 static void kvm_get_preset_lpj(void) 117 { 118 unsigned long khz; 119 u64 lpj; 120 121 khz = kvm_get_tsc_khz(); 122 123 lpj = ((u64)khz * 1000); 124 do_div(lpj, HZ); 125 preset_lpj = lpj; 126 } 127 128 bool kvm_check_and_clear_guest_paused(void) 129 { 130 bool ret = false; 131 struct pvclock_vcpu_time_info *src; 132 int cpu = smp_processor_id(); 133 134 if (!hv_clock) 135 return ret; 136 137 src = &hv_clock[cpu].pvti; 138 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 139 src->flags &= ~PVCLOCK_GUEST_STOPPED; 140 pvclock_touch_watchdogs(); 141 ret = true; 142 } 143 144 return ret; 145 } 146 147 static struct clocksource kvm_clock = { 148 .name = "kvm-clock", 149 .read = kvm_clock_get_cycles, 150 .rating = 400, 151 .mask = CLOCKSOURCE_MASK(64), 152 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 153 }; 154 155 int kvm_register_clock(char *txt) 156 { 157 int cpu = smp_processor_id(); 158 int low, high, ret; 159 struct pvclock_vcpu_time_info *src; 160 161 if (!hv_clock) 162 return 0; 163 164 src = &hv_clock[cpu].pvti; 165 low = (int)slow_virt_to_phys(src) | 1; 166 high = ((u64)slow_virt_to_phys(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 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 int size; 222 223 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 224 225 if (!kvm_para_available()) 226 return; 227 228 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 229 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 230 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 231 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 232 return; 233 234 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 235 msr_kvm_system_time, msr_kvm_wall_clock); 236 237 mem = memblock_alloc(size, PAGE_SIZE); 238 if (!mem) 239 return; 240 hv_clock = __va(mem); 241 memset(hv_clock, 0, size); 242 243 if (kvm_register_clock("primary cpu clock")) { 244 hv_clock = NULL; 245 memblock_free(mem, size); 246 return; 247 } 248 pv_time_ops.sched_clock = kvm_clock_read; 249 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 250 x86_platform.get_wallclock = kvm_get_wallclock; 251 x86_platform.set_wallclock = kvm_set_wallclock; 252 #ifdef CONFIG_X86_LOCAL_APIC 253 x86_cpuinit.early_percpu_clock_init = 254 kvm_setup_secondary_clock; 255 #endif 256 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 257 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 258 machine_ops.shutdown = kvm_shutdown; 259 #ifdef CONFIG_KEXEC 260 machine_ops.crash_shutdown = kvm_crash_shutdown; 261 #endif 262 kvm_get_preset_lpj(); 263 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 264 pv_info.name = "KVM"; 265 266 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 267 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 268 } 269 270 int __init kvm_setup_vsyscall_timeinfo(void) 271 { 272 #ifdef CONFIG_X86_64 273 int cpu; 274 int ret; 275 u8 flags; 276 struct pvclock_vcpu_time_info *vcpu_time; 277 unsigned int size; 278 279 if (!hv_clock) 280 return 0; 281 282 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS); 283 284 cpu = get_cpu(); 285 286 vcpu_time = &hv_clock[cpu].pvti; 287 flags = pvclock_read_flags(vcpu_time); 288 289 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) { 290 put_cpu(); 291 return 1; 292 } 293 294 if ((ret = pvclock_init_vsyscall(hv_clock, size))) { 295 put_cpu(); 296 return ret; 297 } 298 299 put_cpu(); 300 301 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 302 #endif 303 return 0; 304 } 305