![Glauber Costa](/assets/img/avatar_default.png)
KVM intends to use paravirt code to calibrate khz. Xen current code will do just fine. So as a first step, factor out code to pvclock.c. Signed-off-by: Glauber Costa <gcosta@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
497 lines
12 KiB
C
497 lines
12 KiB
C
/*
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* Xen time implementation.
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*
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* This is implemented in terms of a clocksource driver which uses
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* the hypervisor clock as a nanosecond timebase, and a clockevent
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* driver which uses the hypervisor's timer mechanism.
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*
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* Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
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*/
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/clocksource.h>
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#include <linux/clockchips.h>
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#include <linux/kernel_stat.h>
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#include <linux/math64.h>
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#include <asm/pvclock.h>
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#include <asm/xen/hypervisor.h>
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#include <asm/xen/hypercall.h>
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#include <xen/events.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/vcpu.h>
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#include "xen-ops.h"
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#define XEN_SHIFT 22
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/* Xen may fire a timer up to this many ns early */
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#define TIMER_SLOP 100000
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#define NS_PER_TICK (1000000000LL / HZ)
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/* runstate info updated by Xen */
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static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);
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/* snapshots of runstate info */
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static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate_snapshot);
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/* unused ns of stolen and blocked time */
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static DEFINE_PER_CPU(u64, residual_stolen);
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static DEFINE_PER_CPU(u64, residual_blocked);
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/* return an consistent snapshot of 64-bit time/counter value */
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static u64 get64(const u64 *p)
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{
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u64 ret;
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if (BITS_PER_LONG < 64) {
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u32 *p32 = (u32 *)p;
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u32 h, l;
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/*
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* Read high then low, and then make sure high is
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* still the same; this will only loop if low wraps
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* and carries into high.
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* XXX some clean way to make this endian-proof?
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*/
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do {
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h = p32[1];
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barrier();
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l = p32[0];
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barrier();
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} while (p32[1] != h);
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ret = (((u64)h) << 32) | l;
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} else
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ret = *p;
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return ret;
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}
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/*
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* Runstate accounting
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*/
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static void get_runstate_snapshot(struct vcpu_runstate_info *res)
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{
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u64 state_time;
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struct vcpu_runstate_info *state;
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BUG_ON(preemptible());
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state = &__get_cpu_var(runstate);
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/*
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* The runstate info is always updated by the hypervisor on
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* the current CPU, so there's no need to use anything
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* stronger than a compiler barrier when fetching it.
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*/
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do {
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state_time = get64(&state->state_entry_time);
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barrier();
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*res = *state;
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barrier();
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} while (get64(&state->state_entry_time) != state_time);
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}
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/* return true when a vcpu could run but has no real cpu to run on */
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bool xen_vcpu_stolen(int vcpu)
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{
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return per_cpu(runstate, vcpu).state == RUNSTATE_runnable;
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}
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static void setup_runstate_info(int cpu)
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{
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struct vcpu_register_runstate_memory_area area;
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area.addr.v = &per_cpu(runstate, cpu);
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if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
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cpu, &area))
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BUG();
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}
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static void do_stolen_accounting(void)
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{
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struct vcpu_runstate_info state;
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struct vcpu_runstate_info *snap;
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s64 blocked, runnable, offline, stolen;
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cputime_t ticks;
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get_runstate_snapshot(&state);
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WARN_ON(state.state != RUNSTATE_running);
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snap = &__get_cpu_var(runstate_snapshot);
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/* work out how much time the VCPU has not been runn*ing* */
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blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked];
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runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];
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offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];
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*snap = state;
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/* Add the appropriate number of ticks of stolen time,
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including any left-overs from last time. Passing NULL to
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account_steal_time accounts the time as stolen. */
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stolen = runnable + offline + __get_cpu_var(residual_stolen);
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if (stolen < 0)
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stolen = 0;
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ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
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__get_cpu_var(residual_stolen) = stolen;
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account_steal_time(NULL, ticks);
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/* Add the appropriate number of ticks of blocked time,
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including any left-overs from last time. Passing idle to
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account_steal_time accounts the time as idle/wait. */
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blocked += __get_cpu_var(residual_blocked);
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if (blocked < 0)
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blocked = 0;
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ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
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__get_cpu_var(residual_blocked) = blocked;
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account_steal_time(idle_task(smp_processor_id()), ticks);
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}
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/*
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* Xen sched_clock implementation. Returns the number of unstolen
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* nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
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* states.
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*/
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unsigned long long xen_sched_clock(void)
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{
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struct vcpu_runstate_info state;
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cycle_t now;
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u64 ret;
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s64 offset;
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/*
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* Ideally sched_clock should be called on a per-cpu basis
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* anyway, so preempt should already be disabled, but that's
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* not current practice at the moment.
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*/
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preempt_disable();
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now = xen_clocksource_read();
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get_runstate_snapshot(&state);
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WARN_ON(state.state != RUNSTATE_running);
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offset = now - state.state_entry_time;
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if (offset < 0)
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offset = 0;
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ret = state.time[RUNSTATE_blocked] +
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state.time[RUNSTATE_running] +
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offset;
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preempt_enable();
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return ret;
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}
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/* Get the TSC speed from Xen */
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unsigned long xen_tsc_khz(void)
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{
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struct pvclock_vcpu_time_info *info =
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&HYPERVISOR_shared_info->vcpu_info[0].time;
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return pvclock_tsc_khz(info);
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}
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cycle_t xen_clocksource_read(void)
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{
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struct pvclock_vcpu_time_info *src;
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cycle_t ret;
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src = &get_cpu_var(xen_vcpu)->time;
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ret = pvclock_clocksource_read(src);
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put_cpu_var(xen_vcpu);
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return ret;
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}
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static void xen_read_wallclock(struct timespec *ts)
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{
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struct shared_info *s = HYPERVISOR_shared_info;
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struct pvclock_wall_clock *wall_clock = &(s->wc);
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struct pvclock_vcpu_time_info *vcpu_time;
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vcpu_time = &get_cpu_var(xen_vcpu)->time;
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pvclock_read_wallclock(wall_clock, vcpu_time, ts);
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put_cpu_var(xen_vcpu);
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}
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unsigned long xen_get_wallclock(void)
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{
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struct timespec ts;
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xen_read_wallclock(&ts);
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return ts.tv_sec;
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}
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int xen_set_wallclock(unsigned long now)
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{
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/* do nothing for domU */
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return -1;
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}
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static struct clocksource xen_clocksource __read_mostly = {
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.name = "xen",
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.rating = 400,
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.read = xen_clocksource_read,
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.mask = ~0,
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.mult = 1<<XEN_SHIFT, /* time directly in nanoseconds */
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.shift = XEN_SHIFT,
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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/*
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Xen clockevent implementation
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Xen has two clockevent implementations:
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The old timer_op one works with all released versions of Xen prior
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to version 3.0.4. This version of the hypervisor provides a
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single-shot timer with nanosecond resolution. However, sharing the
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same event channel is a 100Hz tick which is delivered while the
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vcpu is running. We don't care about or use this tick, but it will
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cause the core time code to think the timer fired too soon, and
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will end up resetting it each time. It could be filtered, but
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doing so has complications when the ktime clocksource is not yet
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the xen clocksource (ie, at boot time).
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The new vcpu_op-based timer interface allows the tick timer period
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to be changed or turned off. The tick timer is not useful as a
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periodic timer because events are only delivered to running vcpus.
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The one-shot timer can report when a timeout is in the past, so
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set_next_event is capable of returning -ETIME when appropriate.
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This interface is used when available.
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*/
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/*
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Get a hypervisor absolute time. In theory we could maintain an
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offset between the kernel's time and the hypervisor's time, and
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apply that to a kernel's absolute timeout. Unfortunately the
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hypervisor and kernel times can drift even if the kernel is using
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the Xen clocksource, because ntp can warp the kernel's clocksource.
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*/
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static s64 get_abs_timeout(unsigned long delta)
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{
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return xen_clocksource_read() + delta;
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}
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static void xen_timerop_set_mode(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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/* unsupported */
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WARN_ON(1);
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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case CLOCK_EVT_MODE_RESUME:
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break;
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case CLOCK_EVT_MODE_UNUSED:
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case CLOCK_EVT_MODE_SHUTDOWN:
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HYPERVISOR_set_timer_op(0); /* cancel timeout */
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break;
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}
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}
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static int xen_timerop_set_next_event(unsigned long delta,
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struct clock_event_device *evt)
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{
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WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
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if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
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BUG();
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/* We may have missed the deadline, but there's no real way of
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knowing for sure. If the event was in the past, then we'll
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get an immediate interrupt. */
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return 0;
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}
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static const struct clock_event_device xen_timerop_clockevent = {
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.name = "xen",
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.features = CLOCK_EVT_FEAT_ONESHOT,
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.max_delta_ns = 0xffffffff,
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.min_delta_ns = TIMER_SLOP,
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.mult = 1,
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.shift = 0,
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.rating = 500,
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.set_mode = xen_timerop_set_mode,
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.set_next_event = xen_timerop_set_next_event,
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};
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static void xen_vcpuop_set_mode(enum clock_event_mode mode,
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struct clock_event_device *evt)
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{
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int cpu = smp_processor_id();
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switch (mode) {
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case CLOCK_EVT_MODE_PERIODIC:
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WARN_ON(1); /* unsupported */
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break;
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case CLOCK_EVT_MODE_ONESHOT:
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if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
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BUG();
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break;
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case CLOCK_EVT_MODE_UNUSED:
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case CLOCK_EVT_MODE_SHUTDOWN:
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if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL) ||
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HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
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BUG();
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break;
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case CLOCK_EVT_MODE_RESUME:
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break;
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}
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}
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static int xen_vcpuop_set_next_event(unsigned long delta,
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struct clock_event_device *evt)
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{
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int cpu = smp_processor_id();
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struct vcpu_set_singleshot_timer single;
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int ret;
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WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
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single.timeout_abs_ns = get_abs_timeout(delta);
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single.flags = VCPU_SSHOTTMR_future;
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ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single);
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BUG_ON(ret != 0 && ret != -ETIME);
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return ret;
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}
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static const struct clock_event_device xen_vcpuop_clockevent = {
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.name = "xen",
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.features = CLOCK_EVT_FEAT_ONESHOT,
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.max_delta_ns = 0xffffffff,
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.min_delta_ns = TIMER_SLOP,
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.mult = 1,
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.shift = 0,
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.rating = 500,
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.set_mode = xen_vcpuop_set_mode,
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.set_next_event = xen_vcpuop_set_next_event,
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};
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static const struct clock_event_device *xen_clockevent =
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&xen_timerop_clockevent;
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static DEFINE_PER_CPU(struct clock_event_device, xen_clock_events);
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static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
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{
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struct clock_event_device *evt = &__get_cpu_var(xen_clock_events);
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irqreturn_t ret;
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ret = IRQ_NONE;
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if (evt->event_handler) {
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evt->event_handler(evt);
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ret = IRQ_HANDLED;
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}
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do_stolen_accounting();
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return ret;
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}
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void xen_setup_timer(int cpu)
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{
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const char *name;
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struct clock_event_device *evt;
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int irq;
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printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
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name = kasprintf(GFP_KERNEL, "timer%d", cpu);
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if (!name)
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name = "<timer kasprintf failed>";
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irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
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IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
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name, NULL);
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evt = &per_cpu(xen_clock_events, cpu);
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memcpy(evt, xen_clockevent, sizeof(*evt));
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evt->cpumask = cpumask_of_cpu(cpu);
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evt->irq = irq;
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setup_runstate_info(cpu);
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}
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void xen_teardown_timer(int cpu)
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{
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struct clock_event_device *evt;
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BUG_ON(cpu == 0);
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evt = &per_cpu(xen_clock_events, cpu);
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unbind_from_irqhandler(evt->irq, NULL);
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}
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void xen_setup_cpu_clockevents(void)
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{
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BUG_ON(preemptible());
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clockevents_register_device(&__get_cpu_var(xen_clock_events));
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}
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void xen_timer_resume(void)
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{
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int cpu;
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if (xen_clockevent != &xen_vcpuop_clockevent)
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return;
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for_each_online_cpu(cpu) {
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if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
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BUG();
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}
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}
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__init void xen_time_init(void)
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{
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int cpu = smp_processor_id();
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clocksource_register(&xen_clocksource);
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if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
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/* Successfully turned off 100Hz tick, so we have the
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vcpuop-based timer interface */
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printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
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xen_clockevent = &xen_vcpuop_clockevent;
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}
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/* Set initial system time with full resolution */
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xen_read_wallclock(&xtime);
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set_normalized_timespec(&wall_to_monotonic,
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-xtime.tv_sec, -xtime.tv_nsec);
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setup_force_cpu_cap(X86_FEATURE_TSC);
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xen_setup_timer(cpu);
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xen_setup_cpu_clockevents();
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}
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