1/******************************************************************************
  2 * arch/ia64/xen/time.c
  3 *
  4 * Copyright (c) 2008 Isaku Yamahata <yamahata at valinux co jp>
  5 *                    VA Linux Systems Japan K.K.
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License as published by
  9 * the Free Software Foundation; either version 2 of the License, or
 10 * (at your option) any later version.
 11 *
 12 * This program is distributed in the hope that it will be useful,
 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 * GNU General Public License for more details.
 16 *
 17 * You should have received a copy of the GNU General Public License
 18 * along with this program; if not, write to the Free Software
 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 20 *
 21 */
 22
 23#include <linux/delay.h>
 24#include <linux/kernel_stat.h>
 25#include <linux/posix-timers.h>
 26#include <linux/irq.h>
 27#include <linux/clocksource.h>
 28
 29#include <asm/timex.h>
 30
 31#include <asm/xen/hypervisor.h>
 32
 33#include <xen/interface/vcpu.h>
 34
 35#include "../kernel/fsyscall_gtod_data.h"
 36
 37static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
 38static DEFINE_PER_CPU(unsigned long, xen_stolen_time);
 39static DEFINE_PER_CPU(unsigned long, xen_blocked_time);
 40
 41/* taken from i386/kernel/time-xen.c */
 42static void xen_init_missing_ticks_accounting(int cpu)
 43{
 44	struct vcpu_register_runstate_memory_area area;
 45	struct vcpu_runstate_info *runstate = &per_cpu(xen_runstate, cpu);
 46	int rc;
 47
 48	memset(runstate, 0, sizeof(*runstate));
 49
 50	area.addr.v = runstate;
 51	rc = HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu,
 52				&area);
 53	WARN_ON(rc && rc != -ENOSYS);
 54
 55	per_cpu(xen_blocked_time, cpu) = runstate->time[RUNSTATE_blocked];
 56	per_cpu(xen_stolen_time, cpu) = runstate->time[RUNSTATE_runnable]
 57					    + runstate->time[RUNSTATE_offline];
 58}
 59
 60/*
 61 * Runstate accounting
 62 */
 63/* stolen from arch/x86/xen/time.c */
 64static void get_runstate_snapshot(struct vcpu_runstate_info *res)
 65{
 66	u64 state_time;
 67	struct vcpu_runstate_info *state;
 68
 69	BUG_ON(preemptible());
 70
 71	state = &__get_cpu_var(xen_runstate);
 72
 73	/*
 74	 * The runstate info is always updated by the hypervisor on
 75	 * the current CPU, so there's no need to use anything
 76	 * stronger than a compiler barrier when fetching it.
 77	 */
 78	do {
 79		state_time = state->state_entry_time;
 80		rmb();
 81		*res = *state;
 82		rmb();
 83	} while (state->state_entry_time != state_time);
 84}
 85
 86#define NS_PER_TICK (1000000000LL/HZ)
 87
 88static unsigned long
 89consider_steal_time(unsigned long new_itm)
 90{
 91	unsigned long stolen, blocked;
 92	unsigned long delta_itm = 0, stolentick = 0;
 93	int cpu = smp_processor_id();
 94	struct vcpu_runstate_info runstate;
 95	struct task_struct *p = current;
 96
 97	get_runstate_snapshot(&runstate);
 98
 99	/*
100	 * Check for vcpu migration effect
101	 * In this case, itc value is reversed.
102	 * This causes huge stolen value.
103	 * This function just checks and reject this effect.
104	 */
105	if (!time_after_eq(runstate.time[RUNSTATE_blocked],
106			   per_cpu(xen_blocked_time, cpu)))
107		blocked = 0;
108
109	if (!time_after_eq(runstate.time[RUNSTATE_runnable] +
110			   runstate.time[RUNSTATE_offline],
111			   per_cpu(xen_stolen_time, cpu)))
112		stolen = 0;
113
114	if (!time_after(delta_itm + new_itm, ia64_get_itc()))
115		stolentick = ia64_get_itc() - new_itm;
116
117	do_div(stolentick, NS_PER_TICK);
118	stolentick++;
119
120	do_div(stolen, NS_PER_TICK);
121
122	if (stolen > stolentick)
123		stolen = stolentick;
124
125	stolentick -= stolen;
126	do_div(blocked, NS_PER_TICK);
127
128	if (blocked > stolentick)
129		blocked = stolentick;
130
131	if (stolen > 0 || blocked > 0) {
132		account_steal_ticks(stolen);
133		account_idle_ticks(blocked);
134		run_local_timers();
135
136		rcu_check_callbacks(cpu, user_mode(get_irq_regs()));
137
138		scheduler_tick();
139		run_posix_cpu_timers(p);
140		delta_itm += local_cpu_data->itm_delta * (stolen + blocked);
141
142		if (cpu == time_keeper_id)
143			xtime_update(stolen + blocked);
144
145		local_cpu_data->itm_next = delta_itm + new_itm;
146
147		per_cpu(xen_stolen_time, cpu) += NS_PER_TICK * stolen;
148		per_cpu(xen_blocked_time, cpu) += NS_PER_TICK * blocked;
149	}
150	return delta_itm;
151}
152
153static int xen_do_steal_accounting(unsigned long *new_itm)
154{
155	unsigned long delta_itm;
156	delta_itm = consider_steal_time(*new_itm);
157	*new_itm += delta_itm;
158	if (time_after(*new_itm, ia64_get_itc()) && delta_itm)
159		return 1;
160
161	return 0;
162}
163
164static void xen_itc_jitter_data_reset(void)
165{
166	u64 lcycle, ret;
167
168	do {
169		lcycle = itc_jitter_data.itc_lastcycle;
170		ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, 0);
171	} while (unlikely(ret != lcycle));
172}
173
174/* based on xen_sched_clock() in arch/x86/xen/time.c. */
175/*
176 * This relies on HAVE_UNSTABLE_SCHED_CLOCK. If it can't be defined,
177 * something similar logic should be implemented here.
178 */
179/*
180 * Xen sched_clock implementation.  Returns the number of unstolen
181 * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
182 * states.
183 */
184static unsigned long long xen_sched_clock(void)
185{
186	struct vcpu_runstate_info runstate;
187
188	unsigned long long now;
189	unsigned long long offset;
190	unsigned long long ret;
191
192	/*
193	 * Ideally sched_clock should be called on a per-cpu basis
194	 * anyway, so preempt should already be disabled, but that's
195	 * not current practice at the moment.
196	 */
197	preempt_disable();
198
199	/*
200	 * both ia64_native_sched_clock() and xen's runstate are
201	 * based on mAR.ITC. So difference of them makes sense.
202	 */
203	now = ia64_native_sched_clock();
204
205	get_runstate_snapshot(&runstate);
206
207	WARN_ON(runstate.state != RUNSTATE_running);
208
209	offset = 0;
210	if (now > runstate.state_entry_time)
211		offset = now - runstate.state_entry_time;
212	ret = runstate.time[RUNSTATE_blocked] +
213		runstate.time[RUNSTATE_running] +
214		offset;
215
216	preempt_enable();
217
218	return ret;
219}
220
221struct pv_time_ops xen_time_ops __initdata = {
222	.init_missing_ticks_accounting	= xen_init_missing_ticks_accounting,
223	.do_steal_accounting		= xen_do_steal_accounting,
224	.clocksource_resume		= xen_itc_jitter_data_reset,
225	.sched_clock			= xen_sched_clock,
226};
227
228/* Called after suspend, to resume time.  */
229static void xen_local_tick_resume(void)
230{
231	/* Just trigger a tick.  */
232	ia64_cpu_local_tick();
233	touch_softlockup_watchdog();
234}
235
236void
237xen_timer_resume(void)
238{
239	unsigned int cpu;
240
241	xen_local_tick_resume();
242
243	for_each_online_cpu(cpu)
244		xen_init_missing_ticks_accounting(cpu);
245}
246
247static void ia64_cpu_local_tick_fn(void *unused)
248{
249	xen_local_tick_resume();
250	xen_init_missing_ticks_accounting(smp_processor_id());
251}
252
253void
254xen_timer_resume_on_aps(void)
255{
256	smp_call_function(&ia64_cpu_local_tick_fn, NULL, 1);
257}