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#define KVM_SCALE 22 30 31static int kvmclock = 1; 32static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; 33static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; 34 35static int parse_no_kvmclock(char *arg) 36{ 37 kvmclock = 0; 38 return 0; 39} 40early_param("no-kvmclock", parse_no_kvmclock); 41 42/* The hypervisor will put information about time periodically here */ 43static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); 44static 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 */ 51static unsigned long kvm_get_wallclock(void) 52{ 53 struct pvclock_vcpu_time_info *vcpu_time; 54 struct timespec ts; 55 int low, high; 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 vcpu_time = &get_cpu_var(hv_clock); 63 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); 64 put_cpu_var(hv_clock); 65 66 return ts.tv_sec; 67} 68 69static int kvm_set_wallclock(unsigned long now) 70{ 71 return -1; 72} 73 74static cycle_t kvm_clock_read(void) 75{ 76 struct pvclock_vcpu_time_info *src; 77 cycle_t ret; 78 79 src = &get_cpu_var(hv_clock); 80 ret = pvclock_clocksource_read(src); 81 put_cpu_var(hv_clock); 82 return ret; 83} 84 85static 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 */ 99static 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 106static 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 118static struct clocksource kvm_clock = { 119 .name = "kvm-clock", 120 .read = kvm_clock_get_cycles, 121 .rating = 400, 122 .mask = CLOCKSOURCE_MASK(64), 123 .mult = 1 << KVM_SCALE, 124 .shift = KVM_SCALE, 125 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 126}; 127 128static int kvm_register_clock(char *txt) 129{ 130 int cpu = smp_processor_id(); 131 int low, high; 132 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; 133 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); 134 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 135 cpu, high, low, txt); 136 137 return native_write_msr_safe(msr_kvm_system_time, low, high); 138} 139 140#ifdef CONFIG_X86_LOCAL_APIC 141static void __cpuinit kvm_setup_secondary_clock(void) 142{ 143 /* 144 * Now that the first cpu already had this clocksource initialized, 145 * we shouldn't fail. 146 */ 147 WARN_ON(kvm_register_clock("secondary cpu clock")); 148 /* ok, done with our trickery, call native */ 149 setup_secondary_APIC_clock(); 150} 151#endif 152 153#ifdef CONFIG_SMP 154static void __init kvm_smp_prepare_boot_cpu(void) 155{ 156 WARN_ON(kvm_register_clock("primary cpu clock")); 157 native_smp_prepare_boot_cpu(); 158} 159#endif 160 161/* 162 * After the clock is registered, the host will keep writing to the 163 * registered memory location. If the guest happens to shutdown, this memory 164 * won't be valid. In cases like kexec, in which you install a new kernel, this 165 * means a random memory location will be kept being written. So before any 166 * kind of shutdown from our side, we unregister the clock by writting anything 167 * that does not have the 'enable' bit set in the msr 168 */ 169#ifdef CONFIG_KEXEC 170static void kvm_crash_shutdown(struct pt_regs *regs) 171{ 172 native_write_msr(msr_kvm_system_time, 0, 0); 173 native_machine_crash_shutdown(regs); 174} 175#endif 176 177static void kvm_shutdown(void) 178{ 179 native_write_msr(msr_kvm_system_time, 0, 0); 180 native_machine_shutdown(); 181} 182 183void __init kvmclock_init(void) 184{ 185 if (!kvm_para_available()) 186 return; 187 188 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 189 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 190 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 191 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 192 return; 193 194 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 195 msr_kvm_system_time, msr_kvm_wall_clock); 196 197 if (kvm_register_clock("boot clock")) 198 return; 199 pv_time_ops.sched_clock = kvm_clock_read; 200 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 201 x86_platform.get_wallclock = kvm_get_wallclock; 202 x86_platform.set_wallclock = kvm_set_wallclock; 203#ifdef CONFIG_X86_LOCAL_APIC 204 x86_cpuinit.setup_percpu_clockev = 205 kvm_setup_secondary_clock; 206#endif 207#ifdef CONFIG_SMP 208 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; 209#endif 210 machine_ops.shutdown = kvm_shutdown; 211#ifdef CONFIG_KEXEC 212 machine_ops.crash_shutdown = kvm_crash_shutdown; 213#endif 214 kvm_get_preset_lpj(); 215 clocksource_register(&kvm_clock); 216 pv_info.paravirt_enabled = 1; 217 pv_info.name = "KVM"; 218 219 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 220 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 221} 222