/drivers/clocksource/hyperv_timer.c
C | 475 lines | 267 code | 67 blank | 141 comment | 20 complexity | c4dc454c00e4b0299fba77eb87440408 MD5 | raw file
Possible License(s): GPL-2.0
- // SPDX-License-Identifier: GPL-2.0
- /*
- * Clocksource driver for the synthetic counter and timers
- * provided by the Hyper-V hypervisor to guest VMs, as described
- * in the Hyper-V Top Level Functional Spec (TLFS). This driver
- * is instruction set architecture independent.
- *
- * Copyright (C) 2019, Microsoft, Inc.
- *
- * Author: Michael Kelley <mikelley@microsoft.com>
- */
- #include <linux/percpu.h>
- #include <linux/cpumask.h>
- #include <linux/clockchips.h>
- #include <linux/clocksource.h>
- #include <linux/sched_clock.h>
- #include <linux/mm.h>
- #include <linux/cpuhotplug.h>
- #include <clocksource/hyperv_timer.h>
- #include <asm/hyperv-tlfs.h>
- #include <asm/mshyperv.h>
- static struct clock_event_device __percpu *hv_clock_event;
- static u64 hv_sched_clock_offset __ro_after_init;
- /*
- * If false, we're using the old mechanism for stimer0 interrupts
- * where it sends a VMbus message when it expires. The old
- * mechanism is used when running on older versions of Hyper-V
- * that don't support Direct Mode. While Hyper-V provides
- * four stimer's per CPU, Linux uses only stimer0.
- *
- * Because Direct Mode does not require processing a VMbus
- * message, stimer interrupts can be enabled earlier in the
- * process of booting a CPU, and consistent with when timer
- * interrupts are enabled for other clocksource drivers.
- * However, for legacy versions of Hyper-V when Direct Mode
- * is not enabled, setting up stimer interrupts must be
- * delayed until VMbus is initialized and can process the
- * interrupt message.
- */
- static bool direct_mode_enabled;
- static int stimer0_irq;
- static int stimer0_vector;
- static int stimer0_message_sint;
- /*
- * ISR for when stimer0 is operating in Direct Mode. Direct Mode
- * does not use VMbus or any VMbus messages, so process here and not
- * in the VMbus driver code.
- */
- void hv_stimer0_isr(void)
- {
- struct clock_event_device *ce;
- ce = this_cpu_ptr(hv_clock_event);
- ce->event_handler(ce);
- }
- EXPORT_SYMBOL_GPL(hv_stimer0_isr);
- static int hv_ce_set_next_event(unsigned long delta,
- struct clock_event_device *evt)
- {
- u64 current_tick;
- current_tick = hv_read_reference_counter();
- current_tick += delta;
- hv_init_timer(0, current_tick);
- return 0;
- }
- static int hv_ce_shutdown(struct clock_event_device *evt)
- {
- hv_init_timer(0, 0);
- hv_init_timer_config(0, 0);
- if (direct_mode_enabled)
- hv_disable_stimer0_percpu_irq(stimer0_irq);
- return 0;
- }
- static int hv_ce_set_oneshot(struct clock_event_device *evt)
- {
- union hv_stimer_config timer_cfg;
- timer_cfg.as_uint64 = 0;
- timer_cfg.enable = 1;
- timer_cfg.auto_enable = 1;
- if (direct_mode_enabled) {
- /*
- * When it expires, the timer will directly interrupt
- * on the specified hardware vector/IRQ.
- */
- timer_cfg.direct_mode = 1;
- timer_cfg.apic_vector = stimer0_vector;
- hv_enable_stimer0_percpu_irq(stimer0_irq);
- } else {
- /*
- * When it expires, the timer will generate a VMbus message,
- * to be handled by the normal VMbus interrupt handler.
- */
- timer_cfg.direct_mode = 0;
- timer_cfg.sintx = stimer0_message_sint;
- }
- hv_init_timer_config(0, timer_cfg.as_uint64);
- return 0;
- }
- /*
- * hv_stimer_init - Per-cpu initialization of the clockevent
- */
- static int hv_stimer_init(unsigned int cpu)
- {
- struct clock_event_device *ce;
- if (!hv_clock_event)
- return 0;
- ce = per_cpu_ptr(hv_clock_event, cpu);
- ce->name = "Hyper-V clockevent";
- ce->features = CLOCK_EVT_FEAT_ONESHOT;
- ce->cpumask = cpumask_of(cpu);
- ce->rating = 1000;
- ce->set_state_shutdown = hv_ce_shutdown;
- ce->set_state_oneshot = hv_ce_set_oneshot;
- ce->set_next_event = hv_ce_set_next_event;
- clockevents_config_and_register(ce,
- HV_CLOCK_HZ,
- HV_MIN_DELTA_TICKS,
- HV_MAX_MAX_DELTA_TICKS);
- return 0;
- }
- /*
- * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
- */
- int hv_stimer_cleanup(unsigned int cpu)
- {
- struct clock_event_device *ce;
- if (!hv_clock_event)
- return 0;
- /*
- * In the legacy case where Direct Mode is not enabled
- * (which can only be on x86/64), stimer cleanup happens
- * relatively early in the CPU offlining process. We
- * must unbind the stimer-based clockevent device so
- * that the LAPIC timer can take over until clockevents
- * are no longer needed in the offlining process. Note
- * that clockevents_unbind_device() eventually calls
- * hv_ce_shutdown().
- *
- * The unbind should not be done when Direct Mode is
- * enabled because we may be on an architecture where
- * there are no other clockevent devices to fallback to.
- */
- ce = per_cpu_ptr(hv_clock_event, cpu);
- if (direct_mode_enabled)
- hv_ce_shutdown(ce);
- else
- clockevents_unbind_device(ce, cpu);
- return 0;
- }
- EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
- /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
- int hv_stimer_alloc(void)
- {
- int ret = 0;
- /*
- * Synthetic timers are always available except on old versions of
- * Hyper-V on x86. In that case, return as error as Linux will use a
- * clockevent based on emulated LAPIC timer hardware.
- */
- if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
- return -EINVAL;
- hv_clock_event = alloc_percpu(struct clock_event_device);
- if (!hv_clock_event)
- return -ENOMEM;
- direct_mode_enabled = ms_hyperv.misc_features &
- HV_STIMER_DIRECT_MODE_AVAILABLE;
- if (direct_mode_enabled) {
- ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
- hv_stimer0_isr);
- if (ret)
- goto free_percpu;
- /*
- * Since we are in Direct Mode, stimer initialization
- * can be done now with a CPUHP value in the same range
- * as other clockevent devices.
- */
- ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
- "clockevents/hyperv/stimer:starting",
- hv_stimer_init, hv_stimer_cleanup);
- if (ret < 0)
- goto free_stimer0_irq;
- }
- return ret;
- free_stimer0_irq:
- hv_remove_stimer0_irq(stimer0_irq);
- stimer0_irq = 0;
- free_percpu:
- free_percpu(hv_clock_event);
- hv_clock_event = NULL;
- return ret;
- }
- EXPORT_SYMBOL_GPL(hv_stimer_alloc);
- /*
- * hv_stimer_legacy_init -- Called from the VMbus driver to handle
- * the case when Direct Mode is not enabled, and the stimer
- * must be initialized late in the CPU onlining process.
- *
- */
- void hv_stimer_legacy_init(unsigned int cpu, int sint)
- {
- if (direct_mode_enabled)
- return;
- /*
- * This function gets called by each vCPU, so setting the
- * global stimer_message_sint value each time is conceptually
- * not ideal, but the value passed in is always the same and
- * it avoids introducing yet another interface into this
- * clocksource driver just to set the sint in the legacy case.
- */
- stimer0_message_sint = sint;
- (void)hv_stimer_init(cpu);
- }
- EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);
- /*
- * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
- * handle the case when Direct Mode is not enabled, and the
- * stimer must be cleaned up early in the CPU offlining
- * process.
- */
- void hv_stimer_legacy_cleanup(unsigned int cpu)
- {
- if (direct_mode_enabled)
- return;
- (void)hv_stimer_cleanup(cpu);
- }
- EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);
- /* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
- void hv_stimer_free(void)
- {
- if (!hv_clock_event)
- return;
- if (direct_mode_enabled) {
- cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
- hv_remove_stimer0_irq(stimer0_irq);
- stimer0_irq = 0;
- }
- free_percpu(hv_clock_event);
- hv_clock_event = NULL;
- }
- EXPORT_SYMBOL_GPL(hv_stimer_free);
- /*
- * Do a global cleanup of clockevents for the cases of kexec and
- * vmbus exit
- */
- void hv_stimer_global_cleanup(void)
- {
- int cpu;
- /*
- * hv_stime_legacy_cleanup() will stop the stimer if Direct
- * Mode is not enabled, and fallback to the LAPIC timer.
- */
- for_each_present_cpu(cpu) {
- hv_stimer_legacy_cleanup(cpu);
- }
- /*
- * If Direct Mode is enabled, the cpuhp teardown callback
- * (hv_stimer_cleanup) will be run on all CPUs to stop the
- * stimers.
- */
- hv_stimer_free();
- }
- EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
- /*
- * Code and definitions for the Hyper-V clocksources. Two
- * clocksources are defined: one that reads the Hyper-V defined MSR, and
- * the other that uses the TSC reference page feature as defined in the
- * TLFS. The MSR version is for compatibility with old versions of
- * Hyper-V and 32-bit x86. The TSC reference page version is preferred.
- *
- * The Hyper-V clocksource ratings of 250 are chosen to be below the
- * TSC clocksource rating of 300. In configurations where Hyper-V offers
- * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
- * is available and preferred. With the higher rating, it will be the
- * default. On older hardware and Hyper-V versions, the TSC is marked
- * "unstable", so no TSC clocksource is created and the selected Hyper-V
- * clocksource will be the default.
- */
- u64 (*hv_read_reference_counter)(void);
- EXPORT_SYMBOL_GPL(hv_read_reference_counter);
- static union {
- struct ms_hyperv_tsc_page page;
- u8 reserved[PAGE_SIZE];
- } tsc_pg __aligned(PAGE_SIZE);
- struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
- {
- return &tsc_pg.page;
- }
- EXPORT_SYMBOL_GPL(hv_get_tsc_page);
- static u64 notrace read_hv_clock_tsc(void)
- {
- u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());
- if (current_tick == U64_MAX)
- hv_get_time_ref_count(current_tick);
- return current_tick;
- }
- static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
- {
- return read_hv_clock_tsc();
- }
- static u64 notrace read_hv_sched_clock_tsc(void)
- {
- return (read_hv_clock_tsc() - hv_sched_clock_offset) *
- (NSEC_PER_SEC / HV_CLOCK_HZ);
- }
- static void suspend_hv_clock_tsc(struct clocksource *arg)
- {
- u64 tsc_msr;
- /* Disable the TSC page */
- hv_get_reference_tsc(tsc_msr);
- tsc_msr &= ~BIT_ULL(0);
- hv_set_reference_tsc(tsc_msr);
- }
- static void resume_hv_clock_tsc(struct clocksource *arg)
- {
- phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
- u64 tsc_msr;
- /* Re-enable the TSC page */
- hv_get_reference_tsc(tsc_msr);
- tsc_msr &= GENMASK_ULL(11, 0);
- tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
- hv_set_reference_tsc(tsc_msr);
- }
- static int hv_cs_enable(struct clocksource *cs)
- {
- hv_enable_vdso_clocksource();
- return 0;
- }
- static struct clocksource hyperv_cs_tsc = {
- .name = "hyperv_clocksource_tsc_page",
- .rating = 250,
- .read = read_hv_clock_tsc_cs,
- .mask = CLOCKSOURCE_MASK(64),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
- .suspend= suspend_hv_clock_tsc,
- .resume = resume_hv_clock_tsc,
- .enable = hv_cs_enable,
- };
- static u64 notrace read_hv_clock_msr(void)
- {
- u64 current_tick;
- /*
- * Read the partition counter to get the current tick count. This count
- * is set to 0 when the partition is created and is incremented in
- * 100 nanosecond units.
- */
- hv_get_time_ref_count(current_tick);
- return current_tick;
- }
- static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
- {
- return read_hv_clock_msr();
- }
- static u64 notrace read_hv_sched_clock_msr(void)
- {
- return (read_hv_clock_msr() - hv_sched_clock_offset) *
- (NSEC_PER_SEC / HV_CLOCK_HZ);
- }
- static struct clocksource hyperv_cs_msr = {
- .name = "hyperv_clocksource_msr",
- .rating = 250,
- .read = read_hv_clock_msr_cs,
- .mask = CLOCKSOURCE_MASK(64),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
- };
- static bool __init hv_init_tsc_clocksource(void)
- {
- u64 tsc_msr;
- phys_addr_t phys_addr;
- if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
- return false;
- hv_read_reference_counter = read_hv_clock_tsc;
- phys_addr = virt_to_phys(hv_get_tsc_page());
- /*
- * The Hyper-V TLFS specifies to preserve the value of reserved
- * bits in registers. So read the existing value, preserve the
- * low order 12 bits, and add in the guest physical address
- * (which already has at least the low 12 bits set to zero since
- * it is page aligned). Also set the "enable" bit, which is bit 0.
- */
- hv_get_reference_tsc(tsc_msr);
- tsc_msr &= GENMASK_ULL(11, 0);
- tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
- hv_set_reference_tsc(tsc_msr);
- hv_set_clocksource_vdso(hyperv_cs_tsc);
- clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
- hv_sched_clock_offset = hv_read_reference_counter();
- hv_setup_sched_clock(read_hv_sched_clock_tsc);
- return true;
- }
- void __init hv_init_clocksource(void)
- {
- /*
- * Try to set up the TSC page clocksource. If it succeeds, we're
- * done. Otherwise, set up the MSR clocksoruce. At least one of
- * these will always be available except on very old versions of
- * Hyper-V on x86. In that case we won't have a Hyper-V
- * clocksource, but Linux will still run with a clocksource based
- * on the emulated PIT or LAPIC timer.
- */
- if (hv_init_tsc_clocksource())
- return;
- if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))
- return;
- hv_read_reference_counter = read_hv_clock_msr;
- clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
- hv_sched_clock_offset = hv_read_reference_counter();
- hv_setup_sched_clock(read_hv_sched_clock_msr);
- }
- EXPORT_SYMBOL_GPL(hv_init_clocksource);