// 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 <clocksource/hyperv_timer.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
static struct clock_event_device __percpu *hv_clock_event;
/*
* 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.
*/
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 = hyperv_cs->read(NULL);
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
*/
void hv_stimer_init(unsigned int cpu)
{
struct clock_event_device *ce;
/*
* Synthetic timers are always available except on old versions of
* Hyper-V on x86. In that case, just return as Linux will use a
* clocksource based on emulated PIT or LAPIC timer hardware.
*/
if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
return;
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);
}
EXPORT_SYMBOL_GPL(hv_stimer_init);
/*
* hv_stimer_cleanup - Per-cpu cleanup of the clockevent
*/
void hv_stimer_cleanup(unsigned int cpu)
{
struct clock_event_device *ce;
/* Turn off clockevent device */
if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
ce = per_cpu_ptr(hv_clock_event, cpu);
hv_ce_shutdown(ce);
}
}
EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
int hv_stimer_alloc(int sint)
{
int ret;
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) {
free_percpu(hv_clock_event);
hv_clock_event = NULL;
return ret;
}
}
stimer0_message_sint = sint;
return 0;
}
EXPORT_SYMBOL_GPL(hv_stimer_alloc);
/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
void hv_stimer_free(void)
{
if (direct_mode_enabled && (stimer0_irq != 0)) {
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;
struct clock_event_device *ce;
if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
for_each_present_cpu(cpu) {
ce = per_cpu_ptr(hv_clock_event, cpu);
clockevents_unbind_device(ce, cpu);
}
}
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.
*/
struct clocksource *hyperv_cs;
EXPORT_SYMBOL_GPL(hyperv_cs);
#ifdef CONFIG_HYPERV_TSCPAGE
static struct ms_hyperv_tsc_page *tsc_pg;
struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
{
return tsc_pg;
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);
static u64 notrace read_hv_sched_clock_tsc(void)
{
u64 current_tick = hv_read_tsc_page(tsc_pg);
if (current_tick == U64_MAX)
hv_get_time_ref_count(current_tick);
return current_tick;
}
static u64 read_hv_clock_tsc(struct clocksource *arg)
{
return read_hv_sched_clock_tsc();
}
static struct clocksource hyperv_cs_tsc = {
.name = "hyperv_clocksource_tsc_page",
.rating = 400,
.read = read_hv_clock_tsc,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#endif
static u64 notrace read_hv_sched_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 read_hv_clock_msr(struct clocksource *arg)
{
return read_hv_sched_clock_msr();
}
static struct clocksource hyperv_cs_msr = {
.name = "hyperv_clocksource_msr",
.rating = 400,
.read = read_hv_clock_msr,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#ifdef CONFIG_HYPERV_TSCPAGE
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;
tsc_pg = vmalloc(PAGE_SIZE);
if (!tsc_pg)
return false;
hyperv_cs = &hyperv_cs_tsc;
phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
/*
* 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);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
return true;
}
#else
static bool __init hv_init_tsc_clocksource(void)
{
return false;
}
#endif
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;
hyperv_cs = &hyperv_cs_msr;
clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ);
}
EXPORT_SYMBOL_GPL(hv_init_clocksource);
