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