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/*
* Xen time implementation.
*
* This is implemented in terms of a clocksource driver which uses
* the hypervisor clock as a nanosecond timebase, and a clockevent
* driver which uses the hypervisor's timer mechanism.
*
* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
*/
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/pvclock_gtod.h>
#include <linux/timekeeper_internal.h>
#include <asm/pvclock.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/events.h>
#include <xen/features.h>
#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>
#include "xen-ops.h"
/* Xen may fire a timer up to this many ns early */
#define TIMER_SLOP 100000
/* Get the TSC speed from Xen */
static unsigned long xen_tsc_khz(void)
{
struct pvclock_vcpu_time_info *info =
&HYPERVISOR_shared_info->vcpu_info[0].time;
return pvclock_tsc_khz(info);
}
cycle_t xen_clocksource_read(void)
{
struct pvclock_vcpu_time_info *src;
cycle_t ret;
preempt_disable_notrace();
src = &__this_cpu_read(xen_vcpu)->time;
ret = pvclock_clocksource_read(src);
preempt_enable_notrace();
return ret;
}
static cycle_t xen_clocksource_get_cycles(struct clocksource *cs)
{
return xen_clocksource_read();
}
static void xen_read_wallclock(struct timespec *ts)
{
struct shared_info *s = HYPERVISOR_shared_info;
struct pvclock_wall_clock *wall_clock = &(s->wc);
struct pvclock_vcpu_time_info *vcpu_time;
vcpu_time = &get_cpu_var(xen_vcpu)->time;
pvclock_read_wallclock(wall_clock, vcpu_time, ts);
put_cpu_var(xen_vcpu);
}
static void xen_get_wallclock(struct timespec *now)
{
xen_read_wallclock(now);
}
static int xen_set_wallclock(const struct timespec *now)
{
return -1;
}
static int xen_pvclock_gtod_notify(struct notifier_block *nb,
unsigned long was_set, void *priv)
{
/* Protected by the calling core code serialization */
static struct timespec64 next_sync;
struct xen_platform_op op;
struct timespec64 now;
struct timekeeper *tk = priv;
static bool settime64_supported = true;
int ret;
now.tv_sec = tk->xtime_sec;
now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
/*
* We only take the expensive HV call when the clock was set
* or when the 11 minutes RTC synchronization time elapsed.
*/
if (!was_set && timespec64_compare(&now, &next_sync) < 0)
return NOTIFY_OK;
again:
if (settime64_supported) {
op.cmd = XENPF_settime64;
op.u.settime64.mbz = 0;
op.u.settime64.secs = now.tv_sec;
op.u.settime64.nsecs = now.tv_nsec;
op.u.settime64.system_time = xen_clocksource_read();
} else {
op.cmd = XENPF_settime32;
op.u.settime32.secs = now.tv_sec;
op.u.settime32.nsecs = now.tv_nsec;
op.u.settime32.system_time = xen_clocksource_read();
}
ret = HYPERVISOR_platform_op(&op);
if (ret == -ENOSYS && settime64_supported) {
settime64_supported = false;
goto again;
}
if (ret < 0)
return NOTIFY_BAD;
/*
* Move the next drift compensation time 11 minutes
* ahead. That's emulating the sync_cmos_clock() update for
* the hardware RTC.
*/
next_sync = now;
next_sync.tv_sec += 11 * 60;
return NOTIFY_OK;
}
static struct notifier_block xen_pvclock_gtod_notifier = {
.notifier_call = xen_pvclock_gtod_notify,
};
static struct clocksource xen_clocksource __read_mostly = {
.name = "xen",
.rating = 400,
.read = xen_clocksource_get_cycles,
.mask = ~0,
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
/*
Xen clockevent implementation
Xen has two clockevent implementations:
The old timer_op one works with all released versions of Xen prior
to version 3.0.4. This version of the hypervisor provides a
single-shot timer with nanosecond resolution. However, sharing the
same event channel is a 100Hz tick which is delivered while the
vcpu is running. We don't care about or use this tick, but it will
cause the core time code to think the timer fired too soon, and
will end up resetting it each time. It could be filtered, but
doing so has complications when the ktime clocksource is not yet
the xen clocksource (ie, at boot time).
The new vcpu_op-based timer interface allows the tick timer period
to be changed or turned off. The tick timer is not useful as a
periodic timer because events are only delivered to running vcpus.
The one-shot timer can report when a timeout is in the past, so
set_next_event is capable of returning -ETIME when appropriate.
This interface is used when available.
*/
/*
Get a hypervisor absolute time. In theory we could maintain an
offset between the kernel's time and the hypervisor's time, and
apply that to a kernel's absolute timeout. Unfortunately the
hypervisor and kernel times can drift even if the kernel is using
the Xen clocksource, because ntp can warp the kernel's clocksource.
*/
static s64 get_abs_timeout(unsigned long delta)
{
return xen_clocksource_read() + delta;
}
static int xen_timerop_shutdown(struct clock_event_device *evt)
{
/* cancel timeout */
HYPERVISOR_set_timer_op(0);
return 0;
}
static int xen_timerop_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
WARN_ON(!clockevent_state_oneshot(evt));
if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
BUG();
/* We may have missed the deadline, but there's no real way of
knowing for sure. If the event was in the past, then we'll
get an immediate interrupt. */
return 0;
}
static const struct clock_event_device xen_timerop_clockevent = {
.name = "xen",
.features = CLOCK_EVT_FEAT_ONESHOT,
.max_delta_ns = 0xffffffff,
.min_delta_ns = TIMER_SLOP,
.mult = 1,
.shift = 0,
.rating = 500,
.set_state_shutdown = xen_timerop_shutdown,
.set_next_event = xen_timerop_set_next_event,
};
static int xen_vcpuop_shutdown(struct clock_event_device *evt)
{
int cpu = smp_processor_id();
if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, xen_vcpu_nr(cpu),
NULL) ||
HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
NULL))
BUG();
return 0;
}
static int xen_vcpuop_set_oneshot(struct clock_event_device *evt)
{
int cpu = smp_processor_id();
if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
NULL))
BUG();
return 0;
}
static int xen_vcpuop_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
int cpu = smp_processor_id();
struct vcpu_set_singleshot_timer single;
int ret;
WARN_ON(!clockevent_state_oneshot(evt));
single.timeout_abs_ns = get_abs_timeout(delta);
/* Get an event anyway, even if the timeout is already expired */
single.flags = 0;
ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, xen_vcpu_nr(cpu),
&single);
BUG_ON(ret != 0);
return ret;
}
static const struct clock_event_device xen_vcpuop_clockevent = {
.name = "xen",
.features = CLOCK_EVT_FEAT_ONESHOT,
.max_delta_ns = 0xffffffff,
.min_delta_ns = TIMER_SLOP,
.mult = 1,
.shift = 0,
.rating = 500,
.set_state_shutdown = xen_vcpuop_shutdown,
.set_state_oneshot = xen_vcpuop_set_oneshot,
.set_next_event = xen_vcpuop_set_next_event,
};
static const struct clock_event_device *xen_clockevent =
&xen_timerop_clockevent;
struct xen_clock_event_device {
struct clock_event_device evt;
char name[16];
};
static DEFINE_PER_CPU(struct xen_clock_event_device, xen_clock_events) = { .evt.irq = -1 };
static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = this_cpu_ptr(&xen_clock_events.evt);
irqreturn_t ret;
ret = IRQ_NONE;
if (evt->event_handler) {
evt->event_handler(evt);
ret = IRQ_HANDLED;
}
return ret;
}
void xen_teardown_timer(int cpu)
{
struct clock_event_device *evt;
BUG_ON(cpu == 0);
evt = &per_cpu(xen_clock_events
|