root/drivers/clocksource/hyperv_timer.c

DEFINITIONS

1. hv_stimer0_isr
2. hv_ce_set_next_event
3. hv_ce_shutdown
4. hv_ce_set_oneshot
5. hv_stimer_init
6. hv_stimer_cleanup
7. hv_stimer_alloc
8. hv_stimer_free
9. hv_stimer_global_cleanup
10. hv_get_tsc_page
11. read_hv_clock_tsc
12. read_hv_sched_clock_tsc
13. read_hv_clock_msr
14. read_hv_sched_clock_msr
15. hv_init_tsc_clocksource
16. hv_init_clocksource

   1 // SPDX-License-Identifier: GPL-2.0
   2 
   3 /*
   4  * Clocksource driver for the synthetic counter and timers
   5  * provided by the Hyper-V hypervisor to guest VMs, as described
   6  * in the Hyper-V Top Level Functional Spec (TLFS). This driver
   7  * is instruction set architecture independent.
   8  *
   9  * Copyright (C) 2019, Microsoft, Inc.
  10  *
  11  * Author:  Michael Kelley <mikelley@microsoft.com>
  12  */
  13 
  14 #include <linux/percpu.h>
  15 #include <linux/cpumask.h>
  16 #include <linux/clockchips.h>
  17 #include <linux/clocksource.h>
  18 #include <linux/sched_clock.h>
  19 #include <linux/mm.h>
  20 #include <clocksource/hyperv_timer.h>
  21 #include <asm/hyperv-tlfs.h>
  22 #include <asm/mshyperv.h>
  23 
  24 static struct clock_event_device __percpu *hv_clock_event;
  25 static u64 hv_sched_clock_offset __ro_after_init;
  26 
  27 /*
  28  * If false, we're using the old mechanism for stimer0 interrupts
  29  * where it sends a VMbus message when it expires. The old
  30  * mechanism is used when running on older versions of Hyper-V
  31  * that don't support Direct Mode. While Hyper-V provides
  32  * four stimer's per CPU, Linux uses only stimer0.
  33  */
  34 static bool direct_mode_enabled;
  35 
  36 static int stimer0_irq;
  37 static int stimer0_vector;
  38 static int stimer0_message_sint;
  39 
  40 /*
  41  * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
  42  * does not use VMbus or any VMbus messages, so process here and not
  43  * in the VMbus driver code.
  44  */
  45 void hv_stimer0_isr(void)
  46 {
  47         struct clock_event_device *ce;
  48 
  49         ce = this_cpu_ptr(hv_clock_event);
  50         ce->event_handler(ce);
  51 }
  52 EXPORT_SYMBOL_GPL(hv_stimer0_isr);
  53 
  54 static int hv_ce_set_next_event(unsigned long delta,
  55                                 struct clock_event_device *evt)
  56 {
  57         u64 current_tick;
  58 
  59         current_tick = hyperv_cs->read(NULL);
  60         current_tick += delta;
  61         hv_init_timer(0, current_tick);
  62         return 0;
  63 }
  64 
  65 static int hv_ce_shutdown(struct clock_event_device *evt)
  66 {
  67         hv_init_timer(0, 0);
  68         hv_init_timer_config(0, 0);
  69         if (direct_mode_enabled)
  70                 hv_disable_stimer0_percpu_irq(stimer0_irq);
  71 
  72         return 0;
  73 }
  74 
  75 static int hv_ce_set_oneshot(struct clock_event_device *evt)
  76 {
  77         union hv_stimer_config timer_cfg;
  78 
  79         timer_cfg.as_uint64 = 0;
  80         timer_cfg.enable = 1;
  81         timer_cfg.auto_enable = 1;
  82         if (direct_mode_enabled) {
  83                 /*
  84                  * When it expires, the timer will directly interrupt
  85                  * on the specified hardware vector/IRQ.
  86                  */
  87                 timer_cfg.direct_mode = 1;
  88                 timer_cfg.apic_vector = stimer0_vector;
  89                 hv_enable_stimer0_percpu_irq(stimer0_irq);
  90         } else {
  91                 /*
  92                  * When it expires, the timer will generate a VMbus message,
  93                  * to be handled by the normal VMbus interrupt handler.
  94                  */
  95                 timer_cfg.direct_mode = 0;
  96                 timer_cfg.sintx = stimer0_message_sint;
  97         }
  98         hv_init_timer_config(0, timer_cfg.as_uint64);
  99         return 0;
 100 }
 101 
 102 /*
 103  * hv_stimer_init - Per-cpu initialization of the clockevent
 104  */
 105 void hv_stimer_init(unsigned int cpu)
 106 {
 107         struct clock_event_device *ce;
 108 
 109         /*
 110          * Synthetic timers are always available except on old versions of
 111          * Hyper-V on x86.  In that case, just return as Linux will use a
 112          * clocksource based on emulated PIT or LAPIC timer hardware.
 113          */
 114         if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
 115                 return;
 116 
 117         ce = per_cpu_ptr(hv_clock_event, cpu);
 118         ce->name = "Hyper-V clockevent";
 119         ce->features = CLOCK_EVT_FEAT_ONESHOT;
 120         ce->cpumask = cpumask_of(cpu);
 121         ce->rating = 1000;
 122         ce->set_state_shutdown = hv_ce_shutdown;
 123         ce->set_state_oneshot = hv_ce_set_oneshot;
 124         ce->set_next_event = hv_ce_set_next_event;
 125 
 126         clockevents_config_and_register(ce,
 127                                         HV_CLOCK_HZ,
 128                                         HV_MIN_DELTA_TICKS,
 129                                         HV_MAX_MAX_DELTA_TICKS);
 130 }
 131 EXPORT_SYMBOL_GPL(hv_stimer_init);
 132 
 133 /*
 134  * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
 135  */
 136 void hv_stimer_cleanup(unsigned int cpu)
 137 {
 138         struct clock_event_device *ce;
 139 
 140         /* Turn off clockevent device */
 141         if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
 142                 ce = per_cpu_ptr(hv_clock_event, cpu);
 143                 hv_ce_shutdown(ce);
 144         }
 145 }
 146 EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
 147 
 148 /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
 149 int hv_stimer_alloc(int sint)
 150 {
 151         int ret;
 152 
 153         hv_clock_event = alloc_percpu(struct clock_event_device);
 154         if (!hv_clock_event)
 155                 return -ENOMEM;
 156 
 157         direct_mode_enabled = ms_hyperv.misc_features &
 158                         HV_STIMER_DIRECT_MODE_AVAILABLE;
 159         if (direct_mode_enabled) {
 160                 ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
 161                                 hv_stimer0_isr);
 162                 if (ret) {
 163                         free_percpu(hv_clock_event);
 164                         hv_clock_event = NULL;
 165                         return ret;
 166                 }
 167         }
 168 
 169         stimer0_message_sint = sint;
 170         return 0;
 171 }
 172 EXPORT_SYMBOL_GPL(hv_stimer_alloc);
 173 
 174 /* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
 175 void hv_stimer_free(void)
 176 {
 177         if (direct_mode_enabled && (stimer0_irq != 0)) {
 178                 hv_remove_stimer0_irq(stimer0_irq);
 179                 stimer0_irq = 0;
 180         }
 181         free_percpu(hv_clock_event);
 182         hv_clock_event = NULL;
 183 }
 184 EXPORT_SYMBOL_GPL(hv_stimer_free);
 185 
 186 /*
 187  * Do a global cleanup of clockevents for the cases of kexec and
 188  * vmbus exit
 189  */
 190 void hv_stimer_global_cleanup(void)
 191 {
 192         int     cpu;
 193         struct clock_event_device *ce;
 194 
 195         if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
 196                 for_each_present_cpu(cpu) {
 197                         ce = per_cpu_ptr(hv_clock_event, cpu);
 198                         clockevents_unbind_device(ce, cpu);
 199                 }
 200         }
 201         hv_stimer_free();
 202 }
 203 EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
 204 
 205 /*
 206  * Code and definitions for the Hyper-V clocksources.  Two
 207  * clocksources are defined: one that reads the Hyper-V defined MSR, and
 208  * the other that uses the TSC reference page feature as defined in the
 209  * TLFS.  The MSR version is for compatibility with old versions of
 210  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
 211  */
 212 
 213 struct clocksource *hyperv_cs;
 214 EXPORT_SYMBOL_GPL(hyperv_cs);
 215 
 216 static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
 217 
 218 struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
 219 {
 220         return &tsc_pg;
 221 }
 222 EXPORT_SYMBOL_GPL(hv_get_tsc_page);
 223 
 224 static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
 225 {
 226         u64 current_tick = hv_read_tsc_page(&tsc_pg);
 227 
 228         if (current_tick == U64_MAX)
 229                 hv_get_time_ref_count(current_tick);
 230 
 231         return current_tick;
 232 }
 233 
 234 static u64 read_hv_sched_clock_tsc(void)
 235 {
 236         return (read_hv_clock_tsc(NULL) - hv_sched_clock_offset) *
 237                 (NSEC_PER_SEC / HV_CLOCK_HZ);
 238 }
 239 
 240 static struct clocksource hyperv_cs_tsc = {
 241         .name   = "hyperv_clocksource_tsc_page",
 242         .rating = 400,
 243         .read   = read_hv_clock_tsc,
 244         .mask   = CLOCKSOURCE_MASK(64),
 245         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 246 };
 247 
 248 static u64 notrace read_hv_clock_msr(struct clocksource *arg)
 249 {
 250         u64 current_tick;
 251         /*
 252          * Read the partition counter to get the current tick count. This count
 253          * is set to 0 when the partition is created and is incremented in
 254          * 100 nanosecond units.
 255          */
 256         hv_get_time_ref_count(current_tick);
 257         return current_tick;
 258 }
 259 
 260 static u64 read_hv_sched_clock_msr(void)
 261 {
 262         return (read_hv_clock_msr(NULL) - hv_sched_clock_offset) *
 263                 (NSEC_PER_SEC / HV_CLOCK_HZ);
 264 }
 265 
 266 static struct clocksource hyperv_cs_msr = {
 267         .name   = "hyperv_clocksource_msr",
 268         .rating = 400,
 269         .read   = read_hv_clock_msr,
 270         .mask   = CLOCKSOURCE_MASK(64),
 271         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 272 };
 273 
 274 static bool __init hv_init_tsc_clocksource(void)
 275 {
 276         u64             tsc_msr;
 277         phys_addr_t     phys_addr;
 278 
 279         if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
 280                 return false;
 281 
 282         hyperv_cs = &hyperv_cs_tsc;
 283         phys_addr = virt_to_phys(&tsc_pg);
 284 
 285         /*
 286          * The Hyper-V TLFS specifies to preserve the value of reserved
 287          * bits in registers. So read the existing value, preserve the
 288          * low order 12 bits, and add in the guest physical address
 289          * (which already has at least the low 12 bits set to zero since
 290          * it is page aligned). Also set the "enable" bit, which is bit 0.
 291          */
 292         hv_get_reference_tsc(tsc_msr);
 293         tsc_msr &= GENMASK_ULL(11, 0);
 294         tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
 295         hv_set_reference_tsc(tsc_msr);
 296 
 297         hv_set_clocksource_vdso(hyperv_cs_tsc);
 298         clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
 299 
 300         hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
 301         hv_setup_sched_clock(read_hv_sched_clock_tsc);
 302 
 303         return true;
 304 }
 305 
 306 void __init hv_init_clocksource(void)
 307 {
 308         /*
 309          * Try to set up the TSC page clocksource. If it succeeds, we're
 310          * done. Otherwise, set up the MSR clocksoruce.  At least one of
 311          * these will always be available except on very old versions of
 312          * Hyper-V on x86.  In that case we won't have a Hyper-V
 313          * clocksource, but Linux will still run with a clocksource based
 314          * on the emulated PIT or LAPIC timer.
 315          */
 316         if (hv_init_tsc_clocksource())
 317                 return;
 318 
 319         if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))
 320                 return;
 321 
 322         hyperv_cs = &hyperv_cs_msr;
 323         clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
 324 
 325         hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
 326         hv_setup_sched_clock(read_hv_sched_clock_msr);
 327 }
 328 EXPORT_SYMBOL_GPL(hv_init_clocksource);