1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* KVM paravirtual clock driver. A clocksource implementation 3 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc. 4 */ 5 6 #include <linux/clocksource.h> 7 #include <linux/kvm_para.h> 8 #include <asm/pvclock.h> 9 #include <asm/msr.h> 10 #include <asm/apic.h> 11 #include <linux/percpu.h> 12 #include <linux/hardirq.h> 13 #include <linux/cpuhotplug.h> 14 #include <linux/sched.h> 15 #include <linux/sched/clock.h> 16 #include <linux/mm.h> 17 #include <linux/slab.h> 18 #include <linux/set_memory.h> 19 20 #include <asm/hypervisor.h> 21 #include <asm/mem_encrypt.h> 22 #include <asm/x86_init.h> 23 #include <asm/reboot.h> 24 #include <asm/kvmclock.h> 25 26 static int kvmclock __initdata = 1; 27 static int kvmclock_vsyscall __initdata = 1; 28 static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME; 29 static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK; 30 static u64 kvm_sched_clock_offset __ro_after_init; 31 32 static int __init parse_no_kvmclock(char *arg) 33 { 34 kvmclock = 0; 35 return 0; 36 } 37 early_param("no-kvmclock", parse_no_kvmclock); 38 39 static int __init parse_no_kvmclock_vsyscall(char *arg) 40 { 41 kvmclock_vsyscall = 0; 42 return 0; 43 } 44 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall); 45 46 /* Aligned to page sizes to match whats mapped via vsyscalls to userspace */ 47 #define HVC_BOOT_ARRAY_SIZE \ 48 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info)) 49 50 static struct pvclock_vsyscall_time_info 51 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE); 52 static struct pvclock_wall_clock wall_clock __bss_decrypted; 53 static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); 54 static struct pvclock_vsyscall_time_info *hvclock_mem; 55 56 static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void) 57 { 58 return &this_cpu_read(hv_clock_per_cpu)->pvti; 59 } 60 61 static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void) 62 { 63 return this_cpu_read(hv_clock_per_cpu); 64 } 65 66 /* 67 * The wallclock is the time of day when we booted. Since then, some time may 68 * have elapsed since the hypervisor wrote the data. So we try to account for 69 * that with system time 70 */ 71 static void kvm_get_wallclock(struct timespec64 *now) 72 { 73 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock)); 74 preempt_disable(); 75 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now); 76 preempt_enable(); 77 } 78 79 static int kvm_set_wallclock(const struct timespec64 *now) 80 { 81 return -ENODEV; 82 } 83 84 static u64 kvm_clock_read(void) 85 { 86 u64 ret; 87 88 preempt_disable_notrace(); 89 ret = pvclock_clocksource_read(this_cpu_pvti()); 90 preempt_enable_notrace(); 91 return ret; 92 } 93 94 static u64 kvm_clock_get_cycles(struct clocksource *cs) 95 { 96 return kvm_clock_read(); 97 } 98 99 static u64 kvm_sched_clock_read(void) 100 { 101 return kvm_clock_read() - kvm_sched_clock_offset; 102 } 103 104 static inline void kvm_sched_clock_init(bool stable) 105 { 106 if (!stable) 107 clear_sched_clock_stable(); 108 kvm_sched_clock_offset = kvm_clock_read(); 109 pv_ops.time.sched_clock = kvm_sched_clock_read; 110 111 pr_info("kvm-clock: using sched offset of %llu cycles", 112 kvm_sched_clock_offset); 113 114 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 115 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 116 } 117 118 /* 119 * If we don't do that, there is the possibility that the guest 120 * will calibrate under heavy load - thus, getting a lower lpj - 121 * and execute the delays themselves without load. This is wrong, 122 * because no delay loop can finish beforehand. 123 * Any heuristics is subject to fail, because ultimately, a large 124 * poll of guests can be running and trouble each other. So we preset 125 * lpj here 126 */ 127 static unsigned long kvm_get_tsc_khz(void) 128 { 129 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); 130 return pvclock_tsc_khz(this_cpu_pvti()); 131 } 132 133 static void __init kvm_get_preset_lpj(void) 134 { 135 unsigned long khz; 136 u64 lpj; 137 138 khz = kvm_get_tsc_khz(); 139 140 lpj = ((u64)khz * 1000); 141 do_div(lpj, HZ); 142 preset_lpj = lpj; 143 } 144 145 bool kvm_check_and_clear_guest_paused(void) 146 { 147 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 148 bool ret = false; 149 150 if (!src) 151 return ret; 152 153 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) { 154 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED; 155 pvclock_touch_watchdogs(); 156 ret = true; 157 } 158 return ret; 159 } 160 161 static int kvm_cs_enable(struct clocksource *cs) 162 { 163 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK); 164 return 0; 165 } 166 167 struct clocksource kvm_clock = { 168 .name = "kvm-clock", 169 .read = kvm_clock_get_cycles, 170 .rating = 400, 171 .mask = CLOCKSOURCE_MASK(64), 172 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 173 .enable = kvm_cs_enable, 174 }; 175 EXPORT_SYMBOL_GPL(kvm_clock); 176 177 static void kvm_register_clock(char *txt) 178 { 179 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 180 u64 pa; 181 182 if (!src) 183 return; 184 185 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL; 186 wrmsrl(msr_kvm_system_time, pa); 187 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt); 188 } 189 190 static void kvm_save_sched_clock_state(void) 191 { 192 } 193 194 static void kvm_restore_sched_clock_state(void) 195 { 196 kvm_register_clock("primary cpu clock, resume"); 197 } 198 199 #ifdef CONFIG_X86_LOCAL_APIC 200 static void kvm_setup_secondary_clock(void) 201 { 202 kvm_register_clock("secondary cpu clock"); 203 } 204 #endif 205 206 /* 207 * After the clock is registered, the host will keep writing to the 208 * registered memory location. If the guest happens to shutdown, this memory 209 * won't be valid. In cases like kexec, in which you install a new kernel, this 210 * means a random memory location will be kept being written. So before any 211 * kind of shutdown from our side, we unregister the clock by writing anything 212 * that does not have the 'enable' bit set in the msr 213 */ 214 #ifdef CONFIG_KEXEC_CORE 215 static void kvm_crash_shutdown(struct pt_regs *regs) 216 { 217 native_write_msr(msr_kvm_system_time, 0, 0); 218 kvm_disable_steal_time(); 219 native_machine_crash_shutdown(regs); 220 } 221 #endif 222 223 static void kvm_shutdown(void) 224 { 225 native_write_msr(msr_kvm_system_time, 0, 0); 226 kvm_disable_steal_time(); 227 native_machine_shutdown(); 228 } 229 230 static void __init kvmclock_init_mem(void) 231 { 232 unsigned long ncpus; 233 unsigned int order; 234 struct page *p; 235 int r; 236 237 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus()) 238 return; 239 240 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE; 241 order = get_order(ncpus * sizeof(*hvclock_mem)); 242 243 p = alloc_pages(GFP_KERNEL, order); 244 if (!p) { 245 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order)); 246 return; 247 } 248 249 hvclock_mem = page_address(p); 250 251 /* 252 * hvclock is shared between the guest and the hypervisor, must 253 * be mapped decrypted. 254 */ 255 if (sev_active()) { 256 r = set_memory_decrypted((unsigned long) hvclock_mem, 257 1UL << order); 258 if (r) { 259 __free_pages(p, order); 260 hvclock_mem = NULL; 261 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n"); 262 return; 263 } 264 } 265 266 memset(hvclock_mem, 0, PAGE_SIZE << order); 267 } 268 269 static int __init kvm_setup_vsyscall_timeinfo(void) 270 { 271 #ifdef CONFIG_X86_64 272 u8 flags; 273 274 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall) 275 return 0; 276 277 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 278 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) 279 return 0; 280 281 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; 282 #endif 283 284 kvmclock_init_mem(); 285 286 return 0; 287 } 288 early_initcall(kvm_setup_vsyscall_timeinfo); 289 290 static int kvmclock_setup_percpu(unsigned int cpu) 291 { 292 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu); 293 294 /* 295 * The per cpu area setup replicates CPU0 data to all cpu 296 * pointers. So carefully check. CPU0 has been set up in init 297 * already. 298 */ 299 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0))) 300 return 0; 301 302 /* Use the static page for the first CPUs, allocate otherwise */ 303 if (cpu < HVC_BOOT_ARRAY_SIZE) 304 p = &hv_clock_boot[cpu]; 305 else if (hvclock_mem) 306 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE; 307 else 308 return -ENOMEM; 309 310 per_cpu(hv_clock_per_cpu, cpu) = p; 311 return p ? 0 : -ENOMEM; 312 } 313 314 void __init kvmclock_init(void) 315 { 316 u8 flags; 317 318 if (!kvm_para_available() || !kvmclock) 319 return; 320 321 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 322 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 323 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 324 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { 325 return; 326 } 327 328 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu", 329 kvmclock_setup_percpu, NULL) < 0) { 330 return; 331 } 332 333 pr_info("kvm-clock: Using msrs %x and %x", 334 msr_kvm_system_time, msr_kvm_wall_clock); 335 336 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); 337 kvm_register_clock("primary cpu clock"); 338 pvclock_set_pvti_cpu0_va(hv_clock_boot); 339 340 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 341 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 342 343 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 344 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 345 346 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 347 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 348 x86_platform.get_wallclock = kvm_get_wallclock; 349 x86_platform.set_wallclock = kvm_set_wallclock; 350 #ifdef CONFIG_X86_LOCAL_APIC 351 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; 352 #endif 353 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 354 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 355 machine_ops.shutdown = kvm_shutdown; 356 #ifdef CONFIG_KEXEC_CORE 357 machine_ops.crash_shutdown = kvm_crash_shutdown; 358 #endif 359 kvm_get_preset_lpj(); 360 361 /* 362 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate 363 * with P/T states and does not stop in deep C-states. 364 * 365 * Invariant TSC exposed by host means kvmclock is not necessary: 366 * can use TSC as clocksource. 367 * 368 */ 369 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && 370 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && 371 !check_tsc_unstable()) 372 kvm_clock.rating = 299; 373 374 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 375 pv_info.name = "KVM"; 376 } 377