drivers/xen/time.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Xen stolen ticks accounting.
   4  */
   5 #include <linux/kernel.h>
   6 #include <linux/kernel_stat.h>
   7 #include <linux/math64.h>
   8 #include <linux/gfp.h>
   9 #include <linux/slab.h>
  10 #include <linux/static_call.h>
  11
  12 #include <asm/paravirt.h>
  13 #include <asm/xen/hypervisor.h>
  14 #include <asm/xen/hypercall.h>
  15
  16 #include <xen/events.h>
  17 #include <xen/features.h>
  18 #include <xen/interface/xen.h>
  19 #include <xen/interface/vcpu.h>
  20 #include <xen/xen-ops.h>
  21
  22 /* runstate info updated by Xen */
  23 static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
  24
  25 static DEFINE_PER_CPU(u64[4], old_runstate_time);
  26
  27 /* return an consistent snapshot of 64-bit time/counter value */
  28 static u64 get64(const u64 *p)
  29 {
  30         u64 ret;
  31
  32         if (BITS_PER_LONG < 64) {
  33                 u32 *p32 = (u32 *)p;
  34                 u32 h, l, h2;
  35
  36                 /*
  37                  * Read high then low, and then make sure high is
  38                  * still the same; this will only loop if low wraps
  39                  * and carries into high.
  40                  * XXX some clean way to make this endian-proof?
  41                  */
  42                 do {
  43                         h = READ_ONCE(p32[1]);
  44                         l = READ_ONCE(p32[0]);
  45                         h2 = READ_ONCE(p32[1]);
  46                 } while(h2 != h);
  47
  48                 ret = (((u64)h) << 32) | l;
  49         } else
  50                 ret = READ_ONCE(*p);
  51
  52         return ret;
  53 }
  54
  55 static void xen_get_runstate_snapshot_cpu_delta(
  56                               struct vcpu_runstate_info *res, unsigned int cpu)
  57 {
  58         u64 state_time;
  59         struct vcpu_runstate_info *state;
  60
  61         BUG_ON(preemptible());
  62
  63         state = per_cpu_ptr(&xen_runstate, cpu);
  64
  65         do {
  66                 state_time = get64(&state->state_entry_time);
  67                 rmb();  /* Hypervisor might update data. */
  68                 *res = __READ_ONCE(*state);
  69                 rmb();  /* Hypervisor might update data. */
  70         } while (get64(&state->state_entry_time) != state_time ||
  71                  (state_time & XEN_RUNSTATE_UPDATE));
  72 }
  73
  74 static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
  75                                           unsigned int cpu)
  76 {
  77         int i;
  78
  79         xen_get_runstate_snapshot_cpu_delta(res, cpu);
  80
  81         for (i = 0; i < 4; i++)
  82                 res->time[i] += per_cpu(old_runstate_time, cpu)[i];
  83 }
  84
  85 void xen_manage_runstate_time(int action)
  86 {
  87         static struct vcpu_runstate_info *runstate_delta;
  88         struct vcpu_runstate_info state;
  89         int cpu, i;
  90
  91         switch (action) {
  92         case -1: /* backup runstate time before suspend */
  93                 if (unlikely(runstate_delta))
  94                         pr_warn_once("%s: memory leak as runstate_delta is not NULL\n",
  95                                         __func__);
  96
  97                 runstate_delta = kmalloc_array(num_possible_cpus(),
  98                                         sizeof(*runstate_delta),
  99                                         GFP_ATOMIC);
 100                 if (unlikely(!runstate_delta)) {
 101                         pr_warn("%s: failed to allocate runstate_delta\n",
 102                                         __func__);
 103                         return;
 104                 }
 105
 106                 for_each_possible_cpu(cpu) {
 107                         xen_get_runstate_snapshot_cpu_delta(&state, cpu);
 108                         memcpy(runstate_delta[cpu].time, state.time,
 109                                         sizeof(runstate_delta[cpu].time));
 110                 }
 111
 112                 break;
 113
 114         case 0: /* backup runstate time after resume */
 115                 if (unlikely(!runstate_delta)) {
 116                         pr_warn("%s: cannot accumulate runstate time as runstate_delta is NULL\n",
 117                                         __func__);
 118                         return;
 119                 }
 120
 121                 for_each_possible_cpu(cpu) {
 122                         for (i = 0; i < 4; i++)
 123                                 per_cpu(old_runstate_time, cpu)[i] +=
 124                                         runstate_delta[cpu].time[i];
 125                 }
 126
 127                 break;
 128
 129         default: /* do not accumulate runstate time for checkpointing */
 130                 break;
 131         }
 132
 133         if (action != -1 && runstate_delta) {
 134                 kfree(runstate_delta);
 135                 runstate_delta = NULL;
 136         }
 137 }
 138
 139 /*
 140  * Runstate accounting
 141  */
 142 void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
 143 {
 144         xen_get_runstate_snapshot_cpu(res, smp_processor_id());
 145 }
 146
 147 /* return true when a vcpu could run but has no real cpu to run on */
 148 bool xen_vcpu_stolen(int vcpu)
 149 {
 150         return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
 151 }
 152
 153 u64 xen_steal_clock(int cpu)
 154 {
 155         struct vcpu_runstate_info state;
 156
 157         xen_get_runstate_snapshot_cpu(&state, cpu);
 158         return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
 159 }
 160
 161 void xen_setup_runstate_info(int cpu)
 162 {
 163         struct vcpu_register_runstate_memory_area area;
 164
 165         area.addr.v = &per_cpu(xen_runstate, cpu);
 166
 167         if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
 168                                xen_vcpu_nr(cpu), &area))
 169                 BUG();
 170 }
 171
 172 void __init xen_time_setup_guest(void)
 173 {
 174         bool xen_runstate_remote;
 175
 176         xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
 177                                         VMASST_TYPE_runstate_update_flag);
 178
 179         static_call_update(pv_steal_clock, xen_steal_clock);
 180
 181         static_key_slow_inc(&paravirt_steal_enabled);
 182         if (xen_runstate_remote)
 183                 static_key_slow_inc(&paravirt_steal_rq_enabled);
 184 }