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