1 /* KVM paravirtual clock driver. A clocksource implementation 2 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc. 3 4 This program is free software; you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation; either version 2 of the License, or 7 (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program; if not, write to the Free Software 16 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 17 */ 18 19 #include <linux/clocksource.h> 20 #include <linux/kvm_para.h> 21 #include <asm/pvclock.h> 22 #include <asm/msr.h> 23 #include <asm/apic.h> 24 #include <linux/percpu.h> 25 #include <linux/hardirq.h> 26 #include <linux/cpuhotplug.h> 27 #include <linux/sched.h> 28 #include <linux/sched/clock.h> 29 #include <linux/mm.h> 30 #include <linux/slab.h> 31 #include <linux/set_memory.h> 32 33 #include <asm/hypervisor.h> 34 #include <asm/mem_encrypt.h> 35 #include <asm/x86_init.h> 36 #include <asm/reboot.h> 37 #include <asm/kvmclock.h> 38 39 static int kvmclock __initdata = 1; 40 static int kvmclock_vsyscall __initdata = 1; 41 static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME; 42 static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK; 43 static u64 kvm_sched_clock_offset __ro_after_init; 44 45 static int __init parse_no_kvmclock(char *arg) 46 { 47 kvmclock = 0; 48 return 0; 49 } 50 early_param("no-kvmclock", parse_no_kvmclock); 51 52 static int __init parse_no_kvmclock_vsyscall(char *arg) 53 { 54 kvmclock_vsyscall = 0; 55 return 0; 56 } 57 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall); 58 59 /* Aligned to page sizes to match whats mapped via vsyscalls to userspace */ 60 #define HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS) 61 #define HVC_BOOT_ARRAY_SIZE \ 62 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info)) 63 64 static struct pvclock_vsyscall_time_info 65 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE); 66 static struct pvclock_wall_clock wall_clock __bss_decrypted; 67 static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); 68 static struct pvclock_vsyscall_time_info *hvclock_mem; 69 70 static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void) 71 { 72 return &this_cpu_read(hv_clock_per_cpu)->pvti; 73 } 74 75 static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void) 76 { 77 return this_cpu_read(hv_clock_per_cpu); 78 } 79 80 /* 81 * The wallclock is the time of day when we booted. Since then, some time may 82 * have elapsed since the hypervisor wrote the data. So we try to account for 83 * that with system time 84 */ 85 static void kvm_get_wallclock(struct timespec64 *now) 86 { 87 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock)); 88 preempt_disable(); 89 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now); 90 preempt_enable(); 91 } 92 93 static int kvm_set_wallclock(const struct timespec64 *now) 94 { 95 return -ENODEV; 96 } 97 98 static u64 kvm_clock_read(void) 99 { 100 u64 ret; 101 102 preempt_disable_notrace(); 103 ret = pvclock_clocksource_read(this_cpu_pvti()); 104 preempt_enable_notrace(); 105 return ret; 106 } 107 108 static u64 kvm_clock_get_cycles(struct clocksource *cs) 109 { 110 return kvm_clock_read(); 111 } 112 113 static u64 kvm_sched_clock_read(void) 114 { 115 return kvm_clock_read() - kvm_sched_clock_offset; 116 } 117 118 static inline void kvm_sched_clock_init(bool stable) 119 { 120 if (!stable) { 121 pv_ops.time.sched_clock = kvm_clock_read; 122 clear_sched_clock_stable(); 123 return; 124 } 125 126 kvm_sched_clock_offset = kvm_clock_read(); 127 pv_ops.time.sched_clock = kvm_sched_clock_read; 128 129 pr_info("kvm-clock: using sched offset of %llu cycles", 130 kvm_sched_clock_offset); 131 132 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > 133 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); 134 } 135 136 /* 137 * If we don't do that, there is the possibility that the guest 138 * will calibrate under heavy load - thus, getting a lower lpj - 139 * and execute the delays themselves without load. This is wrong, 140 * because no delay loop can finish beforehand. 141 * Any heuristics is subject to fail, because ultimately, a large 142 * poll of guests can be running and trouble each other. So we preset 143 * lpj here 144 */ 145 static unsigned long kvm_get_tsc_khz(void) 146 { 147 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); 148 return pvclock_tsc_khz(this_cpu_pvti()); 149 } 150 151 static void __init kvm_get_preset_lpj(void) 152 { 153 unsigned long khz; 154 u64 lpj; 155 156 khz = kvm_get_tsc_khz(); 157 158 lpj = ((u64)khz * 1000); 159 do_div(lpj, HZ); 160 preset_lpj = lpj; 161 } 162 163 bool kvm_check_and_clear_guest_paused(void) 164 { 165 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 166 bool ret = false; 167 168 if (!src) 169 return ret; 170 171 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) { 172 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED; 173 pvclock_touch_watchdogs(); 174 ret = true; 175 } 176 return ret; 177 } 178 179 struct clocksource kvm_clock = { 180 .name = "kvm-clock", 181 .read = kvm_clock_get_cycles, 182 .rating = 400, 183 .mask = CLOCKSOURCE_MASK(64), 184 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 185 }; 186 EXPORT_SYMBOL_GPL(kvm_clock); 187 188 static void kvm_register_clock(char *txt) 189 { 190 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); 191 u64 pa; 192 193 if (!src) 194 return; 195 196 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL; 197 wrmsrl(msr_kvm_system_time, pa); 198 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt); 199 } 200 201 static void kvm_save_sched_clock_state(void) 202 { 203 } 204 205 static void kvm_restore_sched_clock_state(void) 206 { 207 kvm_register_clock("primary cpu clock, resume"); 208 } 209 210 #ifdef CONFIG_X86_LOCAL_APIC 211 static void kvm_setup_secondary_clock(void) 212 { 213 kvm_register_clock("secondary cpu clock"); 214 } 215 #endif 216 217 /* 218 * After the clock is registered, the host will keep writing to the 219 * registered memory location. If the guest happens to shutdown, this memory 220 * won't be valid. In cases like kexec, in which you install a new kernel, this 221 * means a random memory location will be kept being written. So before any 222 * kind of shutdown from our side, we unregister the clock by writing anything 223 * that does not have the 'enable' bit set in the msr 224 */ 225 #ifdef CONFIG_KEXEC_CORE 226 static void kvm_crash_shutdown(struct pt_regs *regs) 227 { 228 native_write_msr(msr_kvm_system_time, 0, 0); 229 kvm_disable_steal_time(); 230 native_machine_crash_shutdown(regs); 231 } 232 #endif 233 234 static void kvm_shutdown(void) 235 { 236 native_write_msr(msr_kvm_system_time, 0, 0); 237 kvm_disable_steal_time(); 238 native_machine_shutdown(); 239 } 240 241 static void __init kvmclock_init_mem(void) 242 { 243 unsigned long ncpus; 244 unsigned int order; 245 struct page *p; 246 int r; 247 248 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus()) 249 return; 250 251 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE; 252 order = get_order(ncpus * sizeof(*hvclock_mem)); 253 254 p = alloc_pages(GFP_KERNEL, order); 255 if (!p) { 256 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order)); 257 return; 258 } 259 260 hvclock_mem = page_address(p); 261 262 /* 263 * hvclock is shared between the guest and the hypervisor, must 264 * be mapped decrypted. 265 */ 266 if (sev_active()) { 267 r = set_memory_decrypted((unsigned long) hvclock_mem, 268 1UL << order); 269 if (r) { 270 __free_pages(p, order); 271 hvclock_mem = NULL; 272 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n"); 273 return; 274 } 275 } 276 277 memset(hvclock_mem, 0, PAGE_SIZE << order); 278 } 279 280 static int __init kvm_setup_vsyscall_timeinfo(void) 281 { 282 #ifdef CONFIG_X86_64 283 u8 flags; 284 285 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall) 286 return 0; 287 288 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 289 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) 290 return 0; 291 292 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK; 293 #endif 294 295 kvmclock_init_mem(); 296 297 return 0; 298 } 299 early_initcall(kvm_setup_vsyscall_timeinfo); 300 301 static int kvmclock_setup_percpu(unsigned int cpu) 302 { 303 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu); 304 305 /* 306 * The per cpu area setup replicates CPU0 data to all cpu 307 * pointers. So carefully check. CPU0 has been set up in init 308 * already. 309 */ 310 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0))) 311 return 0; 312 313 /* Use the static page for the first CPUs, allocate otherwise */ 314 if (cpu < HVC_BOOT_ARRAY_SIZE) 315 p = &hv_clock_boot[cpu]; 316 else if (hvclock_mem) 317 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE; 318 else 319 return -ENOMEM; 320 321 per_cpu(hv_clock_per_cpu, cpu) = p; 322 return p ? 0 : -ENOMEM; 323 } 324 325 void __init kvmclock_init(void) 326 { 327 u8 flags; 328 329 if (!kvm_para_available() || !kvmclock) 330 return; 331 332 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { 333 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; 334 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; 335 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { 336 return; 337 } 338 339 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu", 340 kvmclock_setup_percpu, NULL) < 0) { 341 return; 342 } 343 344 pr_info("kvm-clock: Using msrs %x and %x", 345 msr_kvm_system_time, msr_kvm_wall_clock); 346 347 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); 348 kvm_register_clock("primary cpu clock"); 349 pvclock_set_pvti_cpu0_va(hv_clock_boot); 350 351 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) 352 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); 353 354 flags = pvclock_read_flags(&hv_clock_boot[0].pvti); 355 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); 356 357 x86_platform.calibrate_tsc = kvm_get_tsc_khz; 358 x86_platform.calibrate_cpu = kvm_get_tsc_khz; 359 x86_platform.get_wallclock = kvm_get_wallclock; 360 x86_platform.set_wallclock = kvm_set_wallclock; 361 #ifdef CONFIG_X86_LOCAL_APIC 362 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; 363 #endif 364 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; 365 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; 366 machine_ops.shutdown = kvm_shutdown; 367 #ifdef CONFIG_KEXEC_CORE 368 machine_ops.crash_shutdown = kvm_crash_shutdown; 369 #endif 370 kvm_get_preset_lpj(); 371 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC); 372 pv_info.name = "KVM"; 373 } 374