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 <linux/hardirq.h> 26 #include <linux/cpuhotplug.h> 27 #include <linux/sched.h> 28 #include <linux/sched/clock.h> 29 #include <linux/mm.h> 30 31 #include <asm/hypervisor.h> 32 #include <asm/mem_encrypt.h> 33 #include <asm/x86_init.h> 34 #include <asm/reboot.h> 35 #include <asm/kvmclock.h> 36 37 static int kvmclock __initdata = 1; 38 static int kvmclock_vsyscall __initdata = 1; 39 static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME; 40 static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK; 41 static u64 kvm_sched_clock_offset __ro_after_init; 42 43 static int __init parse_no_kvmclock(char *arg) 44 { 45 kvmclock = 0; 46 return 0; 47 } 48 early_param("no-kvmclock", parse_no_kvmclock); 49 50 static int __init parse_no_kvmclock_vsyscall(char *arg) 51 { 52 kvmclock_vsyscall = 0; 53 return 0; 54 } 55 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall); 56 57 /* Aligned to page sizes to match whats mapped via vsyscalls to userspace */ 58 #define HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS) 59 #define HVC_BOOT_ARRAY_SIZE \ 60 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info)) 61 62 static struct pvclock_vsyscall_time_info 63 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __aligned(PAGE_SIZE); 64 static struct pvclock_wall_clock wall_clock; 65 static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); 66 67 static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void) 68 { 69 return &this_cpu_read(hv_clock_per_cpu)->pvti; 70 } 71 72 static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void) 73 { 74 return this_cpu_read(hv_clock_per_cpu); 75 } 76 77 /* 78 * The wallclock is the time of day when we booted. Since then, some time may 79 * have elapsed since the hypervisor wrote the data. So we try to account for 80 * that with system time 81 */ 82 static void kvm_get_wallclock(struct timespec64 *now) 83 { 84 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock)); 85 preempt_disable(); 86 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now); 87 preempt_enable(); 88 } 89 90 static int kvm_set_wallclock(const struct timespec64 *now) 91 { 92 return -ENODEV; 93 } 94 95 static u64 kvm_clock_read(void) 96 { 97 u64 ret; 98 99 preempt_disable_notrace(); 100 ret = pvclock_clocksource_read(this_cpu_pvti()); 101 preempt_enable_notrace(); 102 return ret; 103 } 104 105 static u64 kvm_clock_get_cycles(struct clocksource *cs) 106 { 107 return kvm_clock_read(); 108 } 109 110 static u64 kvm_sched_clock_read(void) 111 { 112 return kvm_clock_read() - kvm_sched_clock_offset; 113 } 114 115 static inline void kvm_sched_clock_init(bool stable) 116 { 117 if (!stable) { 118 pv_time_ops.sched_clock = kvm_clock_read; 119 clear_sched_clock_stable(); 120 return; 121 } 122 123 kvm_sched_clock_offset = kvm_clock_read(); 124 pv_time_ops.sched_clock = kvm_sched_clock_read; 125 126 pr_info("kvm-clock: using sched offset of %llu cycles", 127 kvm_sched_clock_offset); 128 129 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 130 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 131 } 132 133 /* 134 * If we don't do that, there is the possibility that the guest 135 * will calibrate under heavy load - thus, getting a lower lpj - 136 * and execute the delays themselves without load. This is wrong, 137 * because no delay loop can finish beforehand. 138 * Any heuristics is subject to fail, because ultimately, a large 139 * poll of guests can be running and trouble each other. So we preset 140 * lpj here 141 */ 142 static unsigned long kvm_get_tsc_khz(void) 143 { 144 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); 145 return pvclock_tsc_khz(this_cpu_pvti()); 146 } 147 148 static void __init kvm_get_preset_lpj(void) 149 { 150 unsigned long khz; 151 u64 lpj; 152 153 khz = kvm_get_tsc_khz(); 154 155 lpj = ((u64)khz * 1000); 156 do_div(lpj, HZ); 157 preset_lpj = lpj; 158 } 159 160 bool kvm_check_and_clear_guest_paused(void) 161 { 162 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 163 bool ret = false; 164 165 if (!src) 166 return ret; 167 168 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) { 169 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED; 170 pvclock_touch_watchdogs(); 171 ret = true; 172 } 173 return ret; 174 } 175 176 struct clocksource kvm_clock = { 177 .name = "kvm-clock", 178 .read = kvm_clock_get_cycles, 179 .rating = 400, 180 .mask = CLOCKSOURCE_MASK(64), 181 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 182 }; 183 EXPORT_SYMBOL_GPL(kvm_clock); 184 185 static void kvm_register_clock(char *txt) 186 { 187 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 188 u64 pa; 189 190 if (!src) 191 return; 192 193 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL; 194 wrmsrl(msr_kvm_system_time, pa); 195 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt); 196 } 197 198 static void kvm_save_sched_clock_state(void) 199 { 200 } 201 202 static void kvm_restore_sched_clock_state(void) 203 { 204 kvm_register_clock("primary cpu clock, resume"); 205 } 206 207 #ifdef CONFIG_X86_LOCAL_APIC 208 static void kvm_setup_secondary_clock(void) 209 { 210 kvm_register_clock("secondary cpu clock"); 211 } 212 #endif 213 214 /* 215 * After the clock is registered, the host will keep writing to the 216 * registered memory location. If the guest happens to shutdown, this memory 217 * won't be valid. In cases like kexec, in which you install a new kernel, this 218 * means a random memory location will be kept being written. So before any 219 * kind of shutdown from our side, we unregister the clock by writing anything 220 * that does not have the 'enable' bit set in the msr 221 */ 222 #ifdef CONFIG_KEXEC_CORE 223 static void kvm_crash_shutdown(struct pt_regs *regs) 224 { 225 native_write_msr(msr_kvm_system_time, 0, 0); 226 kvm_disable_steal_time(); 227 native_machine_crash_shutdown(regs); 228 } 229 #endif 230 231 static void kvm_shutdown(void) 232 { 233 native_write_msr(msr_kvm_system_time, 0, 0); 234 kvm_disable_steal_time(); 235 native_machine_shutdown(); 236 } 237 238 static int __init kvm_setup_vsyscall_timeinfo(void) 239 { 240 #ifdef CONFIG_X86_64 241 u8 flags; 242 243 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall) 244 return 0; 245 246 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 247 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) 248 return 0; 249 250 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 251 #endif 252 return 0; 253 } 254 early_initcall(kvm_setup_vsyscall_timeinfo); 255 256 static int kvmclock_setup_percpu(unsigned int cpu) 257 { 258 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu); 259 260 /* 261 * The per cpu area setup replicates CPU0 data to all cpu 262 * pointers. So carefully check. CPU0 has been set up in init 263 * already. 264 */ 265 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0))) 266 return 0; 267 268 /* Use the static page for the first CPUs, allocate otherwise */ 269 if (cpu < HVC_BOOT_ARRAY_SIZE) 270 p = &hv_clock_boot[cpu]; 271 else 272 p = kzalloc(sizeof(*p), GFP_KERNEL); 273 274 per_cpu(hv_clock_per_cpu, cpu) = p; 275 return p ? 0 : -ENOMEM; 276 } 277 278 void __init kvmclock_init(void) 279 { 280 u8 flags; 281 282 if (!kvm_para_available() || !kvmclock) 283 return; 284 285 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 286 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 287 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 288 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { 289 return; 290 } 291 292 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu", 293 kvmclock_setup_percpu, NULL) < 0) { 294 return; 295 } 296 297 pr_info("kvm-clock: Using msrs %x and %x", 298 msr_kvm_system_time, msr_kvm_wall_clock); 299 300 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); 301 kvm_register_clock("primary cpu clock"); 302 pvclock_set_pvti_cpu0_va(hv_clock_boot); 303 304 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 305 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 306 307 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 308 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 309 310 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 311 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 312 x86_platform.get_wallclock = kvm_get_wallclock; 313 x86_platform.set_wallclock = kvm_set_wallclock; 314 #ifdef CONFIG_X86_LOCAL_APIC 315 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; 316 #endif 317 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 318 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 319 machine_ops.shutdown = kvm_shutdown; 320 #ifdef CONFIG_KEXEC_CORE 321 machine_ops.crash_shutdown = kvm_crash_shutdown; 322 #endif 323 kvm_get_preset_lpj(); 324 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 325 pv_info.name = "KVM"; 326 } 327