arch/ia64/xen/time.c

   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/xen/hypervisor.h>
  30
  31 #include <xen/interface/vcpu.h>
  32
  33 #include "../kernel/fsyscall_gtod_data.h"
  34
  35 DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);
  36 DEFINE_PER_CPU(unsigned long, processed_stolen_time);
  37 DEFINE_PER_CPU(unsigned long, processed_blocked_time);
  38
  39 /* taken from i386/kernel/time-xen.c */
  40 static void xen_init_missing_ticks_accounting(int cpu)
  41 {
  42         struct vcpu_register_runstate_memory_area area;
  43         struct vcpu_runstate_info *runstate = &per_cpu(runstate, cpu);
  44         int rc;
  45
  46         memset(runstate, 0, sizeof(*runstate));
  47
  48         area.addr.v = runstate;
  49         rc = HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, cpu,
  50                                 &area);
  51         WARN_ON(rc && rc != -ENOSYS);
  52
  53         per_cpu(processed_blocked_time, cpu) = runstate->time[RUNSTATE_blocked];
  54         per_cpu(processed_stolen_time, cpu) = runstate->time[RUNSTATE_runnable]
  55                                             + runstate->time[RUNSTATE_offline];
  56 }
  57
  58 /*
  59  * Runstate accounting
  60  */
  61 /* stolen from arch/x86/xen/time.c */
  62 static void get_runstate_snapshot(struct vcpu_runstate_info *res)
  63 {
  64         u64 state_time;
  65         struct vcpu_runstate_info *state;
  66
  67         BUG_ON(preemptible());
  68
  69         state = &__get_cpu_var(runstate);
  70
  71         /*
  72          * The runstate info is always updated by the hypervisor on
  73          * the current CPU, so there's no need to use anything
  74          * stronger than a compiler barrier when fetching it.
  75          */
  76         do {
  77                 state_time = state->state_entry_time;
  78                 rmb();
  79                 *res = *state;
  80                 rmb();
  81         } while (state->state_entry_time != state_time);
  82 }
  83
  84 #define NS_PER_TICK (1000000000LL/HZ)
  85
  86 static unsigned long
  87 consider_steal_time(unsigned long new_itm)
  88 {
  89         unsigned long stolen, blocked;
  90         unsigned long delta_itm = 0, stolentick = 0;
  91         int cpu = smp_processor_id();
  92         struct vcpu_runstate_info runstate;
  93         struct task_struct *p = current;
  94
  95         get_runstate_snapshot(&runstate);
  96
  97         /*
  98          * Check for vcpu migration effect
  99          * In this case, itc value is reversed.
 100          * This causes huge stolen value.
 101          * This function just checks and reject this effect.
 102          */
 103         if (!time_after_eq(runstate.time[RUNSTATE_blocked],
 104                            per_cpu(processed_blocked_time, cpu)))
 105                 blocked = 0;
 106
 107         if (!time_after_eq(runstate.time[RUNSTATE_runnable] +
 108                            runstate.time[RUNSTATE_offline],
 109                            per_cpu(processed_stolen_time, cpu)))
 110                 stolen = 0;
 111
 112         if (!time_after(delta_itm + new_itm, ia64_get_itc()))
 113                 stolentick = ia64_get_itc() - new_itm;
 114
 115         do_div(stolentick, NS_PER_TICK);
 116         stolentick++;
 117
 118         do_div(stolen, NS_PER_TICK);
 119
 120         if (stolen > stolentick)
 121                 stolen = stolentick;
 122
 123         stolentick -= stolen;
 124         do_div(blocked, NS_PER_TICK);
 125
 126         if (blocked > stolentick)
 127                 blocked = stolentick;
 128
 129         if (stolen > 0 || blocked > 0) {
 130                 account_steal_time(NULL, jiffies_to_cputime(stolen));
 131                 account_steal_time(idle_task(cpu), jiffies_to_cputime(blocked));
 132                 run_local_timers();
 133
 134                 if (rcu_pending(cpu))
 135                         rcu_check_callbacks(cpu, user_mode(get_irq_regs()));
 136
 137                 scheduler_tick();
 138                 run_posix_cpu_timers(p);
 139                 delta_itm += local_cpu_data->itm_delta * (stolen + blocked);
 140
 141                 if (cpu == time_keeper_id) {
 142                         write_seqlock(&xtime_lock);
 143                         do_timer(stolen + blocked);
 144                         local_cpu_data->itm_next = delta_itm + new_itm;
 145                         write_sequnlock(&xtime_lock);
 146                 } else {
 147                         local_cpu_data->itm_next = delta_itm + new_itm;
 148                 }
 149                 per_cpu(processed_stolen_time, cpu) += NS_PER_TICK * stolen;
 150                 per_cpu(processed_blocked_time, cpu) += NS_PER_TICK * blocked;
 151         }
 152         return delta_itm;
 153 }
 154
 155 static int xen_do_steal_accounting(unsigned long *new_itm)
 156 {
 157         unsigned long delta_itm;
 158         delta_itm = consider_steal_time(*new_itm);
 159         *new_itm += delta_itm;
 160         if (time_after(*new_itm, ia64_get_itc()) && delta_itm)
 161                 return 1;
 162
 163         return 0;
 164 }
 165
 166 static void xen_itc_jitter_data_reset(void)
 167 {
 168         u64 lcycle, ret;
 169
 170         do {
 171                 lcycle = itc_jitter_data.itc_lastcycle;
 172                 ret = cmpxchg(&itc_jitter_data.itc_lastcycle, lcycle, 0);
 173         } while (unlikely(ret != lcycle));
 174 }
 175
 176 struct pv_time_ops xen_time_ops __initdata = {
 177         .init_missing_ticks_accounting  = xen_init_missing_ticks_accounting,
 178         .do_steal_accounting            = xen_do_steal_accounting,
 179         .clocksource_resume             = xen_itc_jitter_data_reset,
 180 };