| 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 | static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; |
| 33 | static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; |
| 34 | |
| 35 | static int parse_no_kvmclock(char *arg) |
| 36 | { |
| 37 | kvmclock = 0; |
| 38 | return 0; |
| 39 | } |
| 40 | early_param("no-kvmclock", parse_no_kvmclock); |
| 41 | |
| 42 | /* The hypervisor will put information about time periodically here */ |
| 43 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock); |
| 44 | static struct pvclock_wall_clock wall_clock; |
| 45 | |
| 46 | /* |
| 47 | * The wallclock is the time of day when we booted. Since then, some time may |
| 48 | * have elapsed since the hypervisor wrote the data. So we try to account for |
| 49 | * that with system time |
| 50 | */ |
| 51 | static unsigned long kvm_get_wallclock(void) |
| 52 | { |
| 53 | struct pvclock_vcpu_time_info *vcpu_time; |
| 54 | struct timespec ts; |
| 55 | int low, high; |
| 56 | |
| 57 | low = (int)__pa_symbol(&wall_clock); |
| 58 | high = ((u64)__pa_symbol(&wall_clock) >> 32); |
| 59 | |
| 60 | native_write_msr(msr_kvm_wall_clock, low, high); |
| 61 | |
| 62 | vcpu_time = &get_cpu_var(hv_clock); |
| 63 | pvclock_read_wallclock(&wall_clock, vcpu_time, &ts); |
| 64 | put_cpu_var(hv_clock); |
| 65 | |
| 66 | return ts.tv_sec; |
| 67 | } |
| 68 | |
| 69 | static int kvm_set_wallclock(unsigned long now) |
| 70 | { |
| 71 | return -1; |
| 72 | } |
| 73 | |
| 74 | static cycle_t kvm_clock_read(void) |
| 75 | { |
| 76 | struct pvclock_vcpu_time_info *src; |
| 77 | cycle_t ret; |
| 78 | |
| 79 | src = &get_cpu_var(hv_clock); |
| 80 | ret = pvclock_clocksource_read(src); |
| 81 | put_cpu_var(hv_clock); |
| 82 | return ret; |
| 83 | } |
| 84 | |
| 85 | static cycle_t kvm_clock_get_cycles(struct clocksource *cs) |
| 86 | { |
| 87 | return kvm_clock_read(); |
| 88 | } |
| 89 | |
| 90 | /* |
| 91 | * If we don't do that, there is the possibility that the guest |
| 92 | * will calibrate under heavy load - thus, getting a lower lpj - |
| 93 | * and execute the delays themselves without load. This is wrong, |
| 94 | * because no delay loop can finish beforehand. |
| 95 | * Any heuristics is subject to fail, because ultimately, a large |
| 96 | * poll of guests can be running and trouble each other. So we preset |
| 97 | * lpj here |
| 98 | */ |
| 99 | static unsigned long kvm_get_tsc_khz(void) |
| 100 | { |
| 101 | struct pvclock_vcpu_time_info *src; |
| 102 | src = &per_cpu(hv_clock, 0); |
| 103 | return pvclock_tsc_khz(src); |
| 104 | } |
| 105 | |
| 106 | static void kvm_get_preset_lpj(void) |
| 107 | { |
| 108 | unsigned long khz; |
| 109 | u64 lpj; |
| 110 | |
| 111 | khz = kvm_get_tsc_khz(); |
| 112 | |
| 113 | lpj = ((u64)khz * 1000); |
| 114 | do_div(lpj, HZ); |
| 115 | preset_lpj = lpj; |
| 116 | } |
| 117 | |
| 118 | static struct clocksource kvm_clock = { |
| 119 | .name = "kvm-clock", |
| 120 | .read = kvm_clock_get_cycles, |
| 121 | .rating = 400, |
| 122 | .mask = CLOCKSOURCE_MASK(64), |
| 123 | .mult = 1 << KVM_SCALE, |
| 124 | .shift = KVM_SCALE, |
| 125 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
| 126 | }; |
| 127 | |
| 128 | static int kvm_register_clock(char *txt) |
| 129 | { |
| 130 | int cpu = smp_processor_id(); |
| 131 | int low, high; |
| 132 | low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; |
| 133 | high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); |
| 134 | printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n", |
| 135 | cpu, high, low, txt); |
| 136 | |
| 137 | return native_write_msr_safe(msr_kvm_system_time, low, high); |
| 138 | } |
| 139 | |
| 140 | #ifdef CONFIG_X86_LOCAL_APIC |
| 141 | static void __cpuinit kvm_setup_secondary_clock(void) |
| 142 | { |
| 143 | /* |
| 144 | * Now that the first cpu already had this clocksource initialized, |
| 145 | * we shouldn't fail. |
| 146 | */ |
| 147 | WARN_ON(kvm_register_clock("secondary cpu clock")); |
| 148 | /* ok, done with our trickery, call native */ |
| 149 | setup_secondary_APIC_clock(); |
| 150 | } |
| 151 | #endif |
| 152 | |
| 153 | #ifdef CONFIG_SMP |
| 154 | static void __init kvm_smp_prepare_boot_cpu(void) |
| 155 | { |
| 156 | WARN_ON(kvm_register_clock("primary cpu clock")); |
| 157 | native_smp_prepare_boot_cpu(); |
| 158 | } |
| 159 | #endif |
| 160 | |
| 161 | /* |
| 162 | * After the clock is registered, the host will keep writing to the |
| 163 | * registered memory location. If the guest happens to shutdown, this memory |
| 164 | * won't be valid. In cases like kexec, in which you install a new kernel, this |
| 165 | * means a random memory location will be kept being written. So before any |
| 166 | * kind of shutdown from our side, we unregister the clock by writting anything |
| 167 | * that does not have the 'enable' bit set in the msr |
| 168 | */ |
| 169 | #ifdef CONFIG_KEXEC |
| 170 | static void kvm_crash_shutdown(struct pt_regs *regs) |
| 171 | { |
| 172 | native_write_msr(msr_kvm_system_time, 0, 0); |
| 173 | native_machine_crash_shutdown(regs); |
| 174 | } |
| 175 | #endif |
| 176 | |
| 177 | static void kvm_shutdown(void) |
| 178 | { |
| 179 | native_write_msr(msr_kvm_system_time, 0, 0); |
| 180 | native_machine_shutdown(); |
| 181 | } |
| 182 | |
| 183 | void __init kvmclock_init(void) |
| 184 | { |
| 185 | if (!kvm_para_available()) |
| 186 | return; |
| 187 | |
| 188 | if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { |
| 189 | msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; |
| 190 | msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; |
| 191 | } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE))) |
| 192 | return; |
| 193 | |
| 194 | printk(KERN_INFO "kvm-clock: Using msrs %x and %x", |
| 195 | msr_kvm_system_time, msr_kvm_wall_clock); |
| 196 | |
| 197 | if (kvm_register_clock("boot clock")) |
| 198 | return; |
| 199 | pv_time_ops.sched_clock = kvm_clock_read; |
| 200 | x86_platform.calibrate_tsc = kvm_get_tsc_khz; |
| 201 | x86_platform.get_wallclock = kvm_get_wallclock; |
| 202 | x86_platform.set_wallclock = kvm_set_wallclock; |
| 203 | #ifdef CONFIG_X86_LOCAL_APIC |
| 204 | x86_cpuinit.setup_percpu_clockev = |
| 205 | kvm_setup_secondary_clock; |
| 206 | #endif |
| 207 | #ifdef CONFIG_SMP |
| 208 | smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; |
| 209 | #endif |
| 210 | machine_ops.shutdown = kvm_shutdown; |
| 211 | #ifdef CONFIG_KEXEC |
| 212 | machine_ops.crash_shutdown = kvm_crash_shutdown; |
| 213 | #endif |
| 214 | kvm_get_preset_lpj(); |
| 215 | clocksource_register(&kvm_clock); |
| 216 | pv_info.paravirt_enabled = 1; |
| 217 | pv_info.name = "KVM"; |
| 218 | |
| 219 | if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) |
| 220 | pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); |
| 221 | } |