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 #include <linux/cc_platform.h> 20 21 #include <asm/hypervisor.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 struct pvclock_vsyscall_time_info *hvclock_mem; 53 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); 54 EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu); 55 56 /* 57 * The wallclock is the time of day when we booted. Since then, some time may 58 * have elapsed since the hypervisor wrote the data. So we try to account for 59 * that with system time 60 */ 61 static void kvm_get_wallclock(struct timespec64 *now) 62 { 63 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock)); 64 preempt_disable(); 65 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now); 66 preempt_enable(); 67 } 68 69 static int kvm_set_wallclock(const struct timespec64 *now) 70 { 71 return -ENODEV; 72 } 73 74 static u64 kvm_clock_read(void) 75 { 76 u64 ret; 77 78 preempt_disable_notrace(); 79 ret = pvclock_clocksource_read_nowd(this_cpu_pvti()); 80 preempt_enable_notrace(); 81 return ret; 82 } 83 84 static u64 kvm_clock_get_cycles(struct clocksource *cs) 85 { 86 return kvm_clock_read(); 87 } 88 89 static noinstr u64 kvm_sched_clock_read(void) 90 { 91 return pvclock_clocksource_read_nowd(this_cpu_pvti()) - kvm_sched_clock_offset; 92 } 93 94 static inline void kvm_sched_clock_init(bool stable) 95 { 96 if (!stable) 97 clear_sched_clock_stable(); 98 kvm_sched_clock_offset = kvm_clock_read(); 99 paravirt_set_sched_clock(kvm_sched_clock_read); 100 101 pr_info("kvm-clock: using sched offset of %llu cycles", 102 kvm_sched_clock_offset); 103 104 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 105 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 106 } 107 108 /* 109 * If we don't do that, there is the possibility that the guest 110 * will calibrate under heavy load - thus, getting a lower lpj - 111 * and execute the delays themselves without load. This is wrong, 112 * because no delay loop can finish beforehand. 113 * Any heuristics is subject to fail, because ultimately, a large 114 * poll of guests can be running and trouble each other. So we preset 115 * lpj here 116 */ 117 static unsigned long kvm_get_tsc_khz(void) 118 { 119 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); 120 return pvclock_tsc_khz(this_cpu_pvti()); 121 } 122 123 static void __init kvm_get_preset_lpj(void) 124 { 125 unsigned long khz; 126 u64 lpj; 127 128 khz = kvm_get_tsc_khz(); 129 130 lpj = ((u64)khz * 1000); 131 do_div(lpj, HZ); 132 preset_lpj = lpj; 133 } 134 135 bool kvm_check_and_clear_guest_paused(void) 136 { 137 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 138 bool ret = false; 139 140 if (!src) 141 return ret; 142 143 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) { 144 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED; 145 pvclock_touch_watchdogs(); 146 ret = true; 147 } 148 return ret; 149 } 150 151 static int kvm_cs_enable(struct clocksource *cs) 152 { 153 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK); 154 return 0; 155 } 156 157 struct clocksource kvm_clock = { 158 .name = "kvm-clock", 159 .read = kvm_clock_get_cycles, 160 .rating = 400, 161 .mask = CLOCKSOURCE_MASK(64), 162 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 163 .enable = kvm_cs_enable, 164 }; 165 EXPORT_SYMBOL_GPL(kvm_clock); 166 167 static void kvm_register_clock(char *txt) 168 { 169 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 170 u64 pa; 171 172 if (!src) 173 return; 174 175 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL; 176 wrmsrl(msr_kvm_system_time, pa); 177 pr_debug("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt); 178 } 179 180 static void kvm_save_sched_clock_state(void) 181 { 182 } 183 184 static void kvm_restore_sched_clock_state(void) 185 { 186 kvm_register_clock("primary cpu clock, resume"); 187 } 188 189 #ifdef CONFIG_X86_LOCAL_APIC 190 static void kvm_setup_secondary_clock(void) 191 { 192 kvm_register_clock("secondary cpu clock"); 193 } 194 #endif 195 196 void kvmclock_disable(void) 197 { 198 native_write_msr(msr_kvm_system_time, 0, 0); 199 } 200 201 static void __init kvmclock_init_mem(void) 202 { 203 unsigned long ncpus; 204 unsigned int order; 205 struct page *p; 206 int r; 207 208 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus()) 209 return; 210 211 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE; 212 order = get_order(ncpus * sizeof(*hvclock_mem)); 213 214 p = alloc_pages(GFP_KERNEL, order); 215 if (!p) { 216 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order)); 217 return; 218 } 219 220 hvclock_mem = page_address(p); 221 222 /* 223 * hvclock is shared between the guest and the hypervisor, must 224 * be mapped decrypted. 225 */ 226 if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) { 227 r = set_memory_decrypted((unsigned long) hvclock_mem, 228 1UL << order); 229 if (r) { 230 __free_pages(p, order); 231 hvclock_mem = NULL; 232 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n"); 233 return; 234 } 235 } 236 237 memset(hvclock_mem, 0, PAGE_SIZE << order); 238 } 239 240 static int __init kvm_setup_vsyscall_timeinfo(void) 241 { 242 if (!kvm_para_available() || !kvmclock || nopv) 243 return 0; 244 245 kvmclock_init_mem(); 246 247 #ifdef CONFIG_X86_64 248 if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) { 249 u8 flags; 250 251 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 252 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) 253 return 0; 254 255 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; 256 } 257 #endif 258 259 return 0; 260 } 261 early_initcall(kvm_setup_vsyscall_timeinfo); 262 263 static int kvmclock_setup_percpu(unsigned int cpu) 264 { 265 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu); 266 267 /* 268 * The per cpu area setup replicates CPU0 data to all cpu 269 * pointers. So carefully check. CPU0 has been set up in init 270 * already. 271 */ 272 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0))) 273 return 0; 274 275 /* Use the static page for the first CPUs, allocate otherwise */ 276 if (cpu < HVC_BOOT_ARRAY_SIZE) 277 p = &hv_clock_boot[cpu]; 278 else if (hvclock_mem) 279 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE; 280 else 281 return -ENOMEM; 282 283 per_cpu(hv_clock_per_cpu, cpu) = p; 284 return p ? 0 : -ENOMEM; 285 } 286 287 void __init kvmclock_init(void) 288 { 289 u8 flags; 290 291 if (!kvm_para_available() || !kvmclock) 292 return; 293 294 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 295 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 296 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 297 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { 298 return; 299 } 300 301 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu", 302 kvmclock_setup_percpu, NULL) < 0) { 303 return; 304 } 305 306 pr_info("kvm-clock: Using msrs %x and %x", 307 msr_kvm_system_time, msr_kvm_wall_clock); 308 309 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); 310 kvm_register_clock("primary cpu clock"); 311 pvclock_set_pvti_cpu0_va(hv_clock_boot); 312 313 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 314 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 315 316 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 317 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 318 319 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 320 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 321 x86_platform.get_wallclock = kvm_get_wallclock; 322 x86_platform.set_wallclock = kvm_set_wallclock; 323 #ifdef CONFIG_X86_LOCAL_APIC 324 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; 325 #endif 326 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 327 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 328 kvm_get_preset_lpj(); 329 330 /* 331 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate 332 * with P/T states and does not stop in deep C-states. 333 * 334 * Invariant TSC exposed by host means kvmclock is not necessary: 335 * can use TSC as clocksource. 336 * 337 */ 338 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && 339 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && 340 !check_tsc_unstable()) 341 kvm_clock.rating = 299; 342 343 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 344 pv_info.name = "KVM"; 345 } 346