1 /*
2 * Xen stolen ticks accounting.
3 */
4 #include <linux/kernel.h>
5 #include <linux/kernel_stat.h>
6 #include <linux/math64.h>
7 #include <linux/gfp.h>
8
9 #include <asm/paravirt.h>
10 #include <asm/xen/hypervisor.h>
11 #include <asm/xen/hypercall.h>
12
13 #include <xen/events.h>
14 #include <xen/features.h>
15 #include <xen/interface/xen.h>
16 #include <xen/interface/vcpu.h>
17 #include <xen/xen-ops.h>
18
19 /* runstate info updated by Xen */
20 static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
21
22 /* return an consistent snapshot of 64-bit time/counter value */
get64(const u64 * p)23 static u64 get64(const u64 *p)
24 {
25 u64 ret;
26
27 if (BITS_PER_LONG < 64) {
28 u32 *p32 = (u32 *)p;
29 u32 h, l, h2;
30
31 /*
32 * Read high then low, and then make sure high is
33 * still the same; this will only loop if low wraps
34 * and carries into high.
35 * XXX some clean way to make this endian-proof?
36 */
37 do {
38 h = READ_ONCE(p32[1]);
39 l = READ_ONCE(p32[0]);
40 h2 = READ_ONCE(p32[1]);
41 } while(h2 != h);
42
43 ret = (((u64)h) << 32) | l;
44 } else
45 ret = READ_ONCE(*p);
46
47 return ret;
48 }
49
xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info * res,unsigned int cpu)50 static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
51 unsigned int cpu)
52 {
53 u64 state_time;
54 struct vcpu_runstate_info *state;
55
56 BUG_ON(preemptible());
57
58 state = per_cpu_ptr(&xen_runstate, cpu);
59
60 do {
61 state_time = get64(&state->state_entry_time);
62 rmb(); /* Hypervisor might update data. */
63 *res = READ_ONCE(*state);
64 rmb(); /* Hypervisor might update data. */
65 } while (get64(&state->state_entry_time) != state_time ||
66 (state_time & XEN_RUNSTATE_UPDATE));
67 }
68
69 /*
70 * Runstate accounting
71 */
xen_get_runstate_snapshot(struct vcpu_runstate_info * res)72 void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
73 {
74 xen_get_runstate_snapshot_cpu(res, smp_processor_id());
75 }
76
77 /* return true when a vcpu could run but has no real cpu to run on */
xen_vcpu_stolen(int vcpu)78 bool xen_vcpu_stolen(int vcpu)
79 {
80 return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
81 }
82
xen_steal_clock(int cpu)83 u64 xen_steal_clock(int cpu)
84 {
85 struct vcpu_runstate_info state;
86
87 xen_get_runstate_snapshot_cpu(&state, cpu);
88 return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
89 }
90
xen_setup_runstate_info(int cpu)91 void xen_setup_runstate_info(int cpu)
92 {
93 struct vcpu_register_runstate_memory_area area;
94
95 area.addr.v = &per_cpu(xen_runstate, cpu);
96
97 if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
98 xen_vcpu_nr(cpu), &area))
99 BUG();
100 }
101
xen_time_setup_guest(void)102 void __init xen_time_setup_guest(void)
103 {
104 bool xen_runstate_remote;
105
106 xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
107 VMASST_TYPE_runstate_update_flag);
108
109 pv_time_ops.steal_clock = xen_steal_clock;
110
111 static_key_slow_inc(¶virt_steal_enabled);
112 if (xen_runstate_remote)
113 static_key_slow_inc(¶virt_steal_rq_enabled);
114 }
115