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;
  28 static int msr_kvm_wall_clock __ro_after_init;
  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 HV_CLOCK_SIZE   (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS)
  47 #define HVC_BOOT_ARRAY_SIZE \
  48         (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
  49
  50 static struct pvclock_vsyscall_time_info
  51                         hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
  52 static struct pvclock_wall_clock wall_clock __bss_decrypted;
  53 static struct pvclock_vsyscall_time_info *hvclock_mem;
  54 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
  55 EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu);
  56
  57 /*
  58  * The wallclock is the time of day when we booted. Since then, some time may
  59  * have elapsed since the hypervisor wrote the data. So we try to account for
  60  * that with system time
  61  */
  62 static void kvm_get_wallclock(struct timespec64 *now)
  63 {
  64         wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
  65         preempt_disable();
  66         pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
  67         preempt_enable();
  68 }
  69
  70 static int kvm_set_wallclock(const struct timespec64 *now)
  71 {
  72         return -ENODEV;
  73 }
  74
  75 static u64 kvm_clock_read(void)
  76 {
  77         u64 ret;
  78
  79         preempt_disable_notrace();
  80         ret = pvclock_clocksource_read(this_cpu_pvti());
  81         preempt_enable_notrace();
  82         return ret;
  83 }
  84
  85 static u64 kvm_clock_get_cycles(struct clocksource *cs)
  86 {
  87         return kvm_clock_read();
  88 }
  89
  90 static u64 kvm_sched_clock_read(void)
  91 {
  92         return kvm_clock_read() - kvm_sched_clock_offset;
  93 }
  94
  95 static inline void kvm_sched_clock_init(bool stable)
  96 {
  97         if (!stable)
  98                 clear_sched_clock_stable();
  99         kvm_sched_clock_offset = kvm_clock_read();
 100         pv_ops.time.sched_clock = kvm_sched_clock_read;
 101
 102         pr_info("kvm-clock: using sched offset of %llu cycles",
 103                 kvm_sched_clock_offset);
 104
 105         BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
 106                 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
 107 }
 108
 109 /*
 110  * If we don't do that, there is the possibility that the guest
 111  * will calibrate under heavy load - thus, getting a lower lpj -
 112  * and execute the delays themselves without load. This is wrong,
 113  * because no delay loop can finish beforehand.
 114  * Any heuristics is subject to fail, because ultimately, a large
 115  * poll of guests can be running and trouble each other. So we preset
 116  * lpj here
 117  */
 118 static unsigned long kvm_get_tsc_khz(void)
 119 {
 120         setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
 121         return pvclock_tsc_khz(this_cpu_pvti());
 122 }
 123
 124 static void __init kvm_get_preset_lpj(void)
 125 {
 126         unsigned long khz;
 127         u64 lpj;
 128
 129         khz = kvm_get_tsc_khz();
 130
 131         lpj = ((u64)khz * 1000);
 132         do_div(lpj, HZ);
 133         preset_lpj = lpj;
 134 }
 135
 136 bool kvm_check_and_clear_guest_paused(void)
 137 {
 138         struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
 139         bool ret = false;
 140
 141         if (!src)
 142                 return ret;
 143
 144         if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
 145                 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
 146                 pvclock_touch_watchdogs();
 147                 ret = true;
 148         }
 149         return ret;
 150 }
 151
 152 static int kvm_cs_enable(struct clocksource *cs)
 153 {
 154         vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
 155         return 0;
 156 }
 157
 158 struct clocksource kvm_clock = {
 159         .name   = "kvm-clock",
 160         .read   = kvm_clock_get_cycles,
 161         .rating = 400,
 162         .mask   = CLOCKSOURCE_MASK(64),
 163         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 164         .enable = kvm_cs_enable,
 165 };
 166 EXPORT_SYMBOL_GPL(kvm_clock);
 167
 168 static void kvm_register_clock(char *txt)
 169 {
 170         struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
 171         u64 pa;
 172
 173         if (!src)
 174                 return;
 175
 176         pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
 177         wrmsrl(msr_kvm_system_time, pa);
 178         pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
 179 }
 180
 181 static void kvm_save_sched_clock_state(void)
 182 {
 183 }
 184
 185 static void kvm_restore_sched_clock_state(void)
 186 {
 187         kvm_register_clock("primary cpu clock, resume");
 188 }
 189
 190 #ifdef CONFIG_X86_LOCAL_APIC
 191 static void kvm_setup_secondary_clock(void)
 192 {
 193         kvm_register_clock("secondary cpu clock");
 194 }
 195 #endif
 196
 197 void kvmclock_disable(void)
 198 {
 199         if (msr_kvm_system_time)
 200                 native_write_msr(msr_kvm_system_time, 0, 0);
 201 }
 202
 203 static void __init kvmclock_init_mem(void)
 204 {
 205         unsigned long ncpus;
 206         unsigned int order;
 207         struct page *p;
 208         int r;
 209
 210         if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
 211                 return;
 212
 213         ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
 214         order = get_order(ncpus * sizeof(*hvclock_mem));
 215
 216         p = alloc_pages(GFP_KERNEL, order);
 217         if (!p) {
 218                 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
 219                 return;
 220         }
 221
 222         hvclock_mem = page_address(p);
 223
 224         /*
 225          * hvclock is shared between the guest and the hypervisor, must
 226          * be mapped decrypted.
 227          */
 228         if (sev_active()) {
 229                 r = set_memory_decrypted((unsigned long) hvclock_mem,
 230                                          1UL << order);
 231                 if (r) {
 232                         __free_pages(p, order);
 233                         hvclock_mem = NULL;
 234                         pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
 235                         return;
 236                 }
 237         }
 238
 239         memset(hvclock_mem, 0, PAGE_SIZE << order);
 240 }
 241
 242 static int __init kvm_setup_vsyscall_timeinfo(void)
 243 {
 244         kvmclock_init_mem();
 245
 246 #ifdef CONFIG_X86_64
 247         if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
 248                 u8 flags;
 249
 250                 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
 251                 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
 252                         return 0;
 253
 254                 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
 255         }
 256 #endif
 257
 258         return 0;
 259 }
 260 early_initcall(kvm_setup_vsyscall_timeinfo);
 261
 262 static int kvmclock_setup_percpu(unsigned int cpu)
 263 {
 264         struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
 265
 266         /*
 267          * The per cpu area setup replicates CPU0 data to all cpu
 268          * pointers. So carefully check. CPU0 has been set up in init
 269          * already.
 270          */
 271         if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
 272                 return 0;
 273
 274         /* Use the static page for the first CPUs, allocate otherwise */
 275         if (cpu < HVC_BOOT_ARRAY_SIZE)
 276                 p = &hv_clock_boot[cpu];
 277         else if (hvclock_mem)
 278                 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
 279         else
 280                 return -ENOMEM;
 281
 282         per_cpu(hv_clock_per_cpu, cpu) = p;
 283         return p ? 0 : -ENOMEM;
 284 }
 285
 286 void __init kvmclock_init(void)
 287 {
 288         u8 flags;
 289
 290         if (!kvm_para_available() || !kvmclock)
 291                 return;
 292
 293         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
 294                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
 295                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
 296         } else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
 297                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
 298                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
 299         } else {
 300                 return;
 301         }
 302
 303         if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
 304                               kvmclock_setup_percpu, NULL) < 0) {
 305                 return;
 306         }
 307
 308         pr_info("kvm-clock: Using msrs %x and %x",
 309                 msr_kvm_system_time, msr_kvm_wall_clock);
 310
 311         this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
 312         kvm_register_clock("primary cpu clock");
 313         pvclock_set_pvti_cpu0_va(hv_clock_boot);
 314
 315         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
 316                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
 317
 318         flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
 319         kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
 320
 321         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
 322         x86_platform.calibrate_cpu = kvm_get_tsc_khz;
 323         x86_platform.get_wallclock = kvm_get_wallclock;
 324         x86_platform.set_wallclock = kvm_set_wallclock;
 325 #ifdef CONFIG_X86_LOCAL_APIC
 326         x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
 327 #endif
 328         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
 329         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
 330         kvm_get_preset_lpj();
 331
 332         /*
 333          * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
 334          * with P/T states and does not stop in deep C-states.
 335          *
 336          * Invariant TSC exposed by host means kvmclock is not necessary:
 337          * can use TSC as clocksource.
 338          *
 339          */
 340         if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
 341             boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
 342             !check_tsc_unstable())
 343                 kvm_clock.rating = 299;
 344
 345         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 346         pv_info.name = "KVM";
 347 }