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