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 src = &get_cpu_var(hv_clock); 78 ret = pvclock_clocksource_read(src); 79 put_cpu_var(hv_clock); 80 return ret; 81 } 82 83 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 84 { 85 return kvm_clock_read(); 86 } 87 88 /* 89 * If we don't do that, there is the possibility that the guest 90 * will calibrate under heavy load - thus, getting a lower lpj - 91 * and execute the delays themselves without load. This is wrong, 92 * because no delay loop can finish beforehand. 93 * Any heuristics is subject to fail, because ultimately, a large 94 * poll of guests can be running and trouble each other. So we preset 95 * lpj here 96 */ 97 static unsigned long kvm_get_tsc_khz(void) 98 { 99 struct pvclock_vcpu_time_info *src; 100 src = &per_cpu(hv_clock, 0); 101 return pvclock_tsc_khz(src); 102 } 103 104 static void kvm_get_preset_lpj(void) 105 { 106 unsigned long khz; 107 u64 lpj; 108 109 khz = kvm_get_tsc_khz(); 110 111 lpj = ((u64)khz * 1000); 112 do_div(lpj, HZ); 113 preset_lpj = lpj; 114 } 115 116 static struct clocksource kvm_clock = { 117 .name = "kvm-clock", 118 .read = kvm_clock_get_cycles, 119 .rating = 400, 120 .mask = CLOCKSOURCE_MASK(64), 121 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 122 }; 123 124 int kvm_register_clock(char *txt) 125 { 126 int cpu = smp_processor_id(); 127 int low, high, ret; 128 129 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; 130 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); 131 ret = native_write_msr_safe(msr_kvm_system_time, low, high); 132 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 133 cpu, high, low, txt); 134 135 return ret; 136 } 137 138 #ifdef CONFIG_X86_LOCAL_APIC 139 static void __cpuinit kvm_setup_secondary_clock(void) 140 { 141 /* 142 * Now that the first cpu already had this clocksource initialized, 143 * we shouldn't fail. 144 */ 145 WARN_ON(kvm_register_clock("secondary cpu clock")); 146 /* ok, done with our trickery, call native */ 147 setup_secondary_APIC_clock(); 148 } 149 #endif 150 151 /* 152 * After the clock is registered, the host will keep writing to the 153 * registered memory location. If the guest happens to shutdown, this memory 154 * won't be valid. In cases like kexec, in which you install a new kernel, this 155 * means a random memory location will be kept being written. So before any 156 * kind of shutdown from our side, we unregister the clock by writting anything 157 * that does not have the 'enable' bit set in the msr 158 */ 159 #ifdef CONFIG_KEXEC 160 static void kvm_crash_shutdown(struct pt_regs *regs) 161 { 162 native_write_msr(msr_kvm_system_time, 0, 0); 163 native_machine_crash_shutdown(regs); 164 } 165 #endif 166 167 static void kvm_shutdown(void) 168 { 169 native_write_msr(msr_kvm_system_time, 0, 0); 170 native_machine_shutdown(); 171 } 172 173 void __init kvmclock_init(void) 174 { 175 if (!kvm_para_available()) 176 return; 177 178 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 179 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 180 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 181 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) 182 return; 183 184 printk(KERN_INFO "kvm-clock: Using msrs %x and %x", 185 msr_kvm_system_time, msr_kvm_wall_clock); 186 187 if (kvm_register_clock("boot clock")) 188 return; 189 pv_time_ops.sched_clock = kvm_clock_read; 190 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 191 x86_platform.get_wallclock = kvm_get_wallclock; 192 x86_platform.set_wallclock = kvm_set_wallclock; 193 #ifdef CONFIG_X86_LOCAL_APIC 194 x86_cpuinit.setup_percpu_clockev = 195 kvm_setup_secondary_clock; 196 #endif 197 machine_ops.shutdown = kvm_shutdown; 198 #ifdef CONFIG_KEXEC 199 machine_ops.crash_shutdown = kvm_crash_shutdown; 200 #endif 201 kvm_get_preset_lpj(); 202 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 203 pv_info.paravirt_enabled = 1; 204 pv_info.name = "KVM"; 205 206 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 207 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 208 } 209