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