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 27 #include <asm/x86_init.h> 28 #include <asm/reboot.h> 29 30 static int kvmclock = 1; 31 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; 32 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; 33 34 static int parse_no_kvmclock(char *arg) 35 { 36 kvmclock = 0; 37 return 0; 38 } 39 early_param("no-kvmclock", parse_no_kvmclock); 40 41 /* The hypervisor will put information about time periodically here */ 42 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); 43 static struct pvclock_wall_clock wall_clock; 44 45 /* 46 * The wallclock is the time of day when we booted. Since then, some time may 47 * have elapsed since the hypervisor wrote the data. So we try to account for 48 * that with system time 49 */ 50 static unsigned long kvm_get_wallclock(void) 51 { 52 struct pvclock_vcpu_time_info *vcpu_time; 53 struct timespec ts; 54 int low, high; 55 56 low = (int)__pa_symbol(&wall_clock); 57 high = ((u64)__pa_symbol(&wall_clock) >> 32); 58 59 native_write_msr(msr_kvm_wall_clock, low, high); 60 61 vcpu_time = &get_cpu_var(hv_clock); 62 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); 63 put_cpu_var(hv_clock); 64 65 return ts.tv_sec; 66 } 67 68 static int kvm_set_wallclock(unsigned long now) 69 { 70 return -1; 71 } 72 73 static cycle_t kvm_clock_read(void) 74 { 75 struct pvclock_vcpu_time_info *src; 76 cycle_t ret; 77 78 preempt_disable_notrace(); 79 src = &__get_cpu_var(hv_clock); 80 ret = pvclock_clocksource_read(src); 81 preempt_enable_notrace(); 82 return ret; 83 } 84 85 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 86 { 87 return kvm_clock_read(); 88 } 89 90 /* 91 * If we don't do that, there is the possibility that the guest 92 * will calibrate under heavy load - thus, getting a lower lpj - 93 * and execute the delays themselves without load. This is wrong, 94 * because no delay loop can finish beforehand. 95 * Any heuristics is subject to fail, because ultimately, a large 96 * poll of guests can be running and trouble each other. So we preset 97 * lpj here 98 */ 99 static unsigned long kvm_get_tsc_khz(void) 100 { 101 struct pvclock_vcpu_time_info *src; 102 src = &per_cpu(hv_clock, 0); 103 return pvclock_tsc_khz(src); 104 } 105 106 static void kvm_get_preset_lpj(void) 107 { 108 unsigned long khz; 109 u64 lpj; 110 111 khz = kvm_get_tsc_khz(); 112 113 lpj = ((u64)khz * 1000); 114 do_div(lpj, HZ); 115 preset_lpj = lpj; 116 } 117 118 bool kvm_check_and_clear_guest_paused(void) 119 { 120 bool ret = false; 121 struct pvclock_vcpu_time_info *src; 122 123 /* 124 * per_cpu() is safe here because this function is only called from 125 * timer functions where preemption is already disabled. 126 */ 127 WARN_ON(!in_atomic()); 128 src = &__get_cpu_var(hv_clock); 129 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) { 130 __this_cpu_and(hv_clock.flags, ~PVCLOCK_GUEST_STOPPED); 131 ret = true; 132 } 133 134 return ret; 135 } 136 137 static struct clocksource kvm_clock = { 138 .name = "kvm-clock", 139 .read = kvm_clock_get_cycles, 140 .rating = 400, 141 .mask = CLOCKSOURCE_MASK(64), 142 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 143 }; 144 145 int kvm_register_clock(char *txt) 146 { 147 int cpu = smp_processor_id(); 148 int low, high, ret; 149 150 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; 151 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); 152 ret = native_write_msr_safe(msr_kvm_system_time, low, high); 153 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 154 cpu, high, low, txt); 155 156 return ret; 157 } 158 159 static void kvm_save_sched_clock_state(void) 160 { 161 } 162 163 static void kvm_restore_sched_clock_state(void) 164 { 165 kvm_register_clock("primary cpu clock, resume"); 166 } 167 168 #ifdef CONFIG_X86_LOCAL_APIC 169 static void __cpuinit kvm_setup_secondary_clock(void) 170 { 171 /* 172 * Now that the first cpu already had this clocksource initialized, 173 * we shouldn't fail. 174 */ 175 WARN_ON(kvm_register_clock("secondary cpu clock")); 176 } 177 #endif 178 179 /* 180 * After the clock is registered, the host will keep writing to the 181 * registered memory location. If the guest happens to shutdown, this memory 182 * won't be valid. In cases like kexec, in which you install a new kernel, this 183 * means a random memory location will be kept being written. So before any 184 * kind of shutdown from our side, we unregister the clock by writting anything 185 * that does not have the 'enable' bit set in the msr 186 */ 187 #ifdef CONFIG_KEXEC 188 static void kvm_crash_shutdown(struct pt_regs *regs) 189 { 190 native_write_msr(msr_kvm_system_time, 0, 0); 191 kvm_disable_steal_time(); 192 native_machine_crash_shutdown(regs); 193 } 194 #endif 195 196 static void kvm_shutdown(void) 197 { 198 native_write_msr(msr_kvm_system_time, 0, 0); 199 kvm_disable_steal_time(); 200 native_machine_shutdown(); 201 } 202 203 void __init kvmclock_init(void) 204 { 205 if (!kvm_para_available()) 206 return; 207 208 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 209 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 210 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 211 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 212 return; 213 214 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 215 msr_kvm_system_time, msr_kvm_wall_clock); 216 217 if (kvm_register_clock("boot clock")) 218 return; 219 pv_time_ops.sched_clock = kvm_clock_read; 220 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 221 x86_platform.get_wallclock = kvm_get_wallclock; 222 x86_platform.set_wallclock = kvm_set_wallclock; 223 #ifdef CONFIG_X86_LOCAL_APIC 224 x86_cpuinit.early_percpu_clock_init = 225 kvm_setup_secondary_clock; 226 #endif 227 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 228 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 229 machine_ops.shutdown = kvm_shutdown; 230 #ifdef CONFIG_KEXEC 231 machine_ops.crash_shutdown = kvm_crash_shutdown; 232 #endif 233 kvm_get_preset_lpj(); 234 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 235 pv_info.paravirt_enabled = 1; 236 pv_info.name = "KVM"; 237 238 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 239 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 240 } 241