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 <asm/reboot.h> 26 27 #define KVM_SCALE 22 28 29 static int kvmclock = 1; 30 31 static int parse_no_kvmclock(char *arg) 32 { 33 kvmclock = 0; 34 return 0; 35 } 36 early_param("no-kvmclock", parse_no_kvmclock); 37 38 /* The hypervisor will put information about time periodically here */ 39 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); 40 static struct pvclock_wall_clock wall_clock; 41 42 /* 43 * The wallclock is the time of day when we booted. Since then, some time may 44 * have elapsed since the hypervisor wrote the data. So we try to account for 45 * that with system time 46 */ 47 static unsigned long kvm_get_wallclock(void) 48 { 49 struct pvclock_vcpu_time_info *vcpu_time; 50 struct timespec ts; 51 int low, high; 52 53 low = (int)__pa(&wall_clock); 54 high = ((u64)__pa(&wall_clock) >> 32); 55 native_write_msr(MSR_KVM_WALL_CLOCK, low, high); 56 57 vcpu_time = &get_cpu_var(hv_clock); 58 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); 59 put_cpu_var(hv_clock); 60 61 return ts.tv_sec; 62 } 63 64 static int kvm_set_wallclock(unsigned long now) 65 { 66 return -1; 67 } 68 69 static cycle_t kvm_clock_read(void) 70 { 71 struct pvclock_vcpu_time_info *src; 72 cycle_t ret; 73 74 src = &get_cpu_var(hv_clock); 75 ret = pvclock_clocksource_read(src); 76 put_cpu_var(hv_clock); 77 return ret; 78 } 79 80 static cycle_t kvm_clock_get_cycles(struct clocksource *cs) 81 { 82 return kvm_clock_read(); 83 } 84 85 /* 86 * If we don't do that, there is the possibility that the guest 87 * will calibrate under heavy load - thus, getting a lower lpj - 88 * and execute the delays themselves without load. This is wrong, 89 * because no delay loop can finish beforehand. 90 * Any heuristics is subject to fail, because ultimately, a large 91 * poll of guests can be running and trouble each other. So we preset 92 * lpj here 93 */ 94 static unsigned long kvm_get_tsc_khz(void) 95 { 96 struct pvclock_vcpu_time_info *src; 97 src = &per_cpu(hv_clock, 0); 98 return pvclock_tsc_khz(src); 99 } 100 101 static void kvm_get_preset_lpj(void) 102 { 103 unsigned long khz; 104 u64 lpj; 105 106 khz = kvm_get_tsc_khz(); 107 108 lpj = ((u64)khz * 1000); 109 do_div(lpj, HZ); 110 preset_lpj = lpj; 111 } 112 113 static struct clocksource kvm_clock = { 114 .name = "kvm-clock", 115 .read = kvm_clock_get_cycles, 116 .rating = 400, 117 .mask = CLOCKSOURCE_MASK(64), 118 .mult = 1 << KVM_SCALE, 119 .shift = KVM_SCALE, 120 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 121 }; 122 123 static int kvm_register_clock(char *txt) 124 { 125 int cpu = smp_processor_id(); 126 int low, high; 127 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; 128 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); 129 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 130 cpu, high, low, txt); 131 return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high); 132 } 133 134 #ifdef CONFIG_X86_LOCAL_APIC 135 static void __cpuinit kvm_setup_secondary_clock(void) 136 { 137 /* 138 * Now that the first cpu already had this clocksource initialized, 139 * we shouldn't fail. 140 */ 141 WARN_ON(kvm_register_clock("secondary cpu clock")); 142 /* ok, done with our trickery, call native */ 143 setup_secondary_APIC_clock(); 144 } 145 #endif 146 147 #ifdef CONFIG_SMP 148 static void __init kvm_smp_prepare_boot_cpu(void) 149 { 150 WARN_ON(kvm_register_clock("primary cpu clock")); 151 native_smp_prepare_boot_cpu(); 152 } 153 #endif 154 155 /* 156 * After the clock is registered, the host will keep writing to the 157 * registered memory location. If the guest happens to shutdown, this memory 158 * won't be valid. In cases like kexec, in which you install a new kernel, this 159 * means a random memory location will be kept being written. So before any 160 * kind of shutdown from our side, we unregister the clock by writting anything 161 * that does not have the 'enable' bit set in the msr 162 */ 163 #ifdef CONFIG_KEXEC 164 static void kvm_crash_shutdown(struct pt_regs *regs) 165 { 166 native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); 167 native_machine_crash_shutdown(regs); 168 } 169 #endif 170 171 static void kvm_shutdown(void) 172 { 173 native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); 174 native_machine_shutdown(); 175 } 176 177 void __init kvmclock_init(void) 178 { 179 if (!kvm_para_available()) 180 return; 181 182 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { 183 if (kvm_register_clock("boot clock")) 184 return; 185 pv_time_ops.get_wallclock = kvm_get_wallclock; 186 pv_time_ops.set_wallclock = kvm_set_wallclock; 187 pv_time_ops.sched_clock = kvm_clock_read; 188 pv_time_ops.get_tsc_khz = kvm_get_tsc_khz; 189 #ifdef CONFIG_X86_LOCAL_APIC 190 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock; 191 #endif 192 #ifdef CONFIG_SMP 193 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; 194 #endif 195 machine_ops.shutdown = kvm_shutdown; 196 #ifdef CONFIG_KEXEC 197 machine_ops.crash_shutdown = kvm_crash_shutdown; 198 #endif 199 kvm_get_preset_lpj(); 200 clocksource_register(&kvm_clock); 201 pv_info.paravirt_enabled = 1; 202 pv_info.name = "KVM"; 203 } 204 } 205