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/arch_hooks.h> 23 #include <asm/msr.h> 24 #include <asm/apic.h> 25 #include <linux/percpu.h> 26 #include <asm/reboot.h> 27 28 #define KVM_SCALE 22 29 30 static int kvmclock = 1; 31 32 static int parse_no_kvmclock(char *arg) 33 { 34 kvmclock = 0; 35 return 0; 36 } 37 early_param("no-kvmclock", parse_no_kvmclock); 38 39 /* The hypervisor will put information about time periodically here */ 40 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); 41 static struct pvclock_wall_clock wall_clock; 42 43 /* 44 * The wallclock is the time of day when we booted. Since then, some time may 45 * have elapsed since the hypervisor wrote the data. So we try to account for 46 * that with system time 47 */ 48 static unsigned long kvm_get_wallclock(void) 49 { 50 struct pvclock_vcpu_time_info *vcpu_time; 51 struct timespec ts; 52 int low, high; 53 54 low = (int)__pa(&wall_clock); 55 high = ((u64)__pa(&wall_clock) >> 32); 56 native_write_msr(MSR_KVM_WALL_CLOCK, low, high); 57 58 vcpu_time = &get_cpu_var(hv_clock); 59 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); 60 put_cpu_var(hv_clock); 61 62 return ts.tv_sec; 63 } 64 65 static int kvm_set_wallclock(unsigned long now) 66 { 67 return -1; 68 } 69 70 static cycle_t kvm_clock_read(void) 71 { 72 struct pvclock_vcpu_time_info *src; 73 cycle_t ret; 74 75 src = &get_cpu_var(hv_clock); 76 ret = pvclock_clocksource_read(src); 77 put_cpu_var(hv_clock); 78 return ret; 79 } 80 81 /* 82 * If we don't do that, there is the possibility that the guest 83 * will calibrate under heavy load - thus, getting a lower lpj - 84 * and execute the delays themselves without load. This is wrong, 85 * because no delay loop can finish beforehand. 86 * Any heuristics is subject to fail, because ultimately, a large 87 * poll of guests can be running and trouble each other. So we preset 88 * lpj here 89 */ 90 static unsigned long kvm_get_tsc_khz(void) 91 { 92 return preset_lpj; 93 } 94 95 static void kvm_get_preset_lpj(void) 96 { 97 struct pvclock_vcpu_time_info *src; 98 unsigned long khz; 99 u64 lpj; 100 101 src = &per_cpu(hv_clock, 0); 102 khz = pvclock_tsc_khz(src); 103 104 lpj = ((u64)khz * 1000); 105 do_div(lpj, HZ); 106 preset_lpj = lpj; 107 } 108 109 static struct clocksource kvm_clock = { 110 .name = "kvm-clock", 111 .read = kvm_clock_read, 112 .rating = 400, 113 .mask = CLOCKSOURCE_MASK(64), 114 .mult = 1 << KVM_SCALE, 115 .shift = KVM_SCALE, 116 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 117 }; 118 119 static int kvm_register_clock(char *txt) 120 { 121 int cpu = smp_processor_id(); 122 int low, high; 123 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; 124 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); 125 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", 126 cpu, high, low, txt); 127 return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high); 128 } 129 130 #ifdef CONFIG_X86_LOCAL_APIC 131 static void kvm_setup_secondary_clock(void) 132 { 133 /* 134 * Now that the first cpu already had this clocksource initialized, 135 * we shouldn't fail. 136 */ 137 WARN_ON(kvm_register_clock("secondary cpu clock")); 138 /* ok, done with our trickery, call native */ 139 setup_secondary_APIC_clock(); 140 } 141 #endif 142 143 #ifdef CONFIG_SMP 144 static void __init kvm_smp_prepare_boot_cpu(void) 145 { 146 WARN_ON(kvm_register_clock("primary cpu clock")); 147 native_smp_prepare_boot_cpu(); 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_safe(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_safe(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_CLOCKSOURCE)) { 179 if (kvm_register_clock("boot clock")) 180 return; 181 pv_time_ops.get_wallclock = kvm_get_wallclock; 182 pv_time_ops.set_wallclock = kvm_set_wallclock; 183 pv_time_ops.sched_clock = kvm_clock_read; 184 pv_time_ops.get_tsc_khz = kvm_get_tsc_khz; 185 #ifdef CONFIG_X86_LOCAL_APIC 186 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock; 187 #endif 188 #ifdef CONFIG_SMP 189 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; 190 #endif 191 machine_ops.shutdown = kvm_shutdown; 192 #ifdef CONFIG_KEXEC 193 machine_ops.crash_shutdown = kvm_crash_shutdown; 194 #endif 195 kvm_get_preset_lpj(); 196 clocksource_register(&kvm_clock); 197 } 198 } 199