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