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 */
get64(const u64 * p)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
xen_get_runstate_snapshot_cpu_delta(struct vcpu_runstate_info * res,unsigned int cpu)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
xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info * res,unsigned int cpu)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
xen_manage_runstate_time(int action)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 */
xen_get_runstate_snapshot(struct vcpu_runstate_info * res)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 */
xen_vcpu_stolen(int vcpu)148 bool xen_vcpu_stolen(int vcpu)
149 {
150 return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
151 }
152
xen_steal_clock(int cpu)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
xen_setup_runstate_info(int cpu)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
xen_time_setup_guest(void)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(¶virt_steal_enabled);
182 if (xen_runstate_remote)
183 static_key_slow_inc(¶virt_steal_rq_enabled);
184 }
185