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// 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);
}