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