arch/x86/kernel/kvmclock.c

   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 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(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 u64 kvm_sched_clock_read(void)
  90 {
  91         return kvm_clock_read() - 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_info("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 (sev_active()) {
 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         kvmclock_init_mem();
 243
 244 #ifdef CONFIG_X86_64
 245         if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
 246                 u8 flags;
 247
 248                 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
 249                 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
 250                         return 0;
 251
 252                 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
 253         }
 254 #endif
 255
 256         return 0;
 257 }
 258 early_initcall(kvm_setup_vsyscall_timeinfo);
 259
 260 static int kvmclock_setup_percpu(unsigned int cpu)
 261 {
 262         struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
 263
 264         /*
 265          * The per cpu area setup replicates CPU0 data to all cpu
 266          * pointers. So carefully check. CPU0 has been set up in init
 267          * already.
 268          */
 269         if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
 270                 return 0;
 271
 272         /* Use the static page for the first CPUs, allocate otherwise */
 273         if (cpu < HVC_BOOT_ARRAY_SIZE)
 274                 p = &hv_clock_boot[cpu];
 275         else if (hvclock_mem)
 276                 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
 277         else
 278                 return -ENOMEM;
 279
 280         per_cpu(hv_clock_per_cpu, cpu) = p;
 281         return p ? 0 : -ENOMEM;
 282 }
 283
 284 void __init kvmclock_init(void)
 285 {
 286         u8 flags;
 287
 288         if (!kvm_para_available() || !kvmclock)
 289                 return;
 290
 291         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 292                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 293                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 294         } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
 295                 return;
 296         }
 297
 298         if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
 299                               kvmclock_setup_percpu, NULL) < 0) {
 300                 return;
 301         }
 302
 303         pr_info("kvm-clock: Using msrs %x and %x",
 304                 msr_kvm_system_time, msr_kvm_wall_clock);
 305
 306         this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
 307         kvm_register_clock("primary cpu clock");
 308         pvclock_set_pvti_cpu0_va(hv_clock_boot);
 309
 310         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 311                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 312
 313         flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
 314         kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
 315
 316         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 317         x86_platform.calibrate_cpu = kvm_get_tsc_khz;
 318         x86_platform.get_wallclock = kvm_get_wallclock;
 319         x86_platform.set_wallclock = kvm_set_wallclock;
 320 #ifdef CONFIG_X86_LOCAL_APIC
 321         x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
 322 #endif
 323         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 324         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
 325         kvm_get_preset_lpj();
 326
 327         /*
 328          * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
 329          * with P/T states and does not stop in deep C-states.
 330          *
 331          * Invariant TSC exposed by host means kvmclock is not necessary:
 332          * can use TSC as clocksource.
 333          *
 334          */
 335         if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
 336             boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
 337             !check_tsc_unstable())
 338                 kvm_clock.rating = 299;
 339
 340         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 341         pv_info.name = "KVM";
 342 }