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