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Linux/arch/ia64/xen/time.c

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  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 
 37 static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
 38 static DEFINE_PER_CPU(unsigned long, xen_stolen_time);
 39 static DEFINE_PER_CPU(unsigned long, xen_blocked_time);
 40 
 41 /* taken from i386/kernel/time-xen.c */
 42 static 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 */
 64 static 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 
 88 static unsigned long
 89 consider_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 
153 static 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 
164 static 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  */
184 static 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 
221 struct 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.  */
229 static void xen_local_tick_resume(void)
230 {
231         /* Just trigger a tick.  */
232         ia64_cpu_local_tick();
233         touch_softlockup_watchdog();
234 }
235 
236 void
237 xen_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 
247 static 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 
253 void
254 xen_timer_resume_on_aps(void)
255 {
256         smp_call_function(&ia64_cpu_local_tick_fn, NULL, 1);
257 }
258 

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