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/xen/hypervisor.h>
10#include <asm/xen/hypercall.h>
11
12#include <xen/events.h>
13#include <xen/features.h>
14#include <xen/interface/xen.h>
15#include <xen/interface/vcpu.h>
16#include <xen/xen-ops.h>
17
18/* runstate info updated by Xen */
19static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
20
21/* return an consistent snapshot of 64-bit time/counter value */
22static u64 get64(const u64 *p)
23{
24	u64 ret;
25
26	if (BITS_PER_LONG < 64) {
27		u32 *p32 = (u32 *)p;
28		u32 h, l, h2;
29
30		/*
31		 * Read high then low, and then make sure high is
32		 * still the same; this will only loop if low wraps
33		 * and carries into high.
34		 * XXX some clean way to make this endian-proof?
35		 */
36		do {
37			h = READ_ONCE(p32[1]);
38			l = READ_ONCE(p32[0]);
39			h2 = READ_ONCE(p32[1]);
40		} while(h2 != h);
41
42		ret = (((u64)h) << 32) | l;
43	} else
44		ret = READ_ONCE(*p);
45
46	return ret;
47}
48
49/*
50 * Runstate accounting
51 */
52void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
53{
54	u64 state_time;
55	struct vcpu_runstate_info *state;
56
57	BUG_ON(preemptible());
58
59	state = this_cpu_ptr(&xen_runstate);
60
61	/*
62	 * The runstate info is always updated by the hypervisor on
63	 * the current CPU, so there's no need to use anything
64	 * stronger than a compiler barrier when fetching it.
65	 */
66	do {
67		state_time = get64(&state->state_entry_time);
68		*res = READ_ONCE(*state);
69	} while (get64(&state->state_entry_time) != state_time);
70}
71
72/* return true when a vcpu could run but has no real cpu to run on */
73bool xen_vcpu_stolen(int vcpu)
74{
75	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
76}
77
78void xen_setup_runstate_info(int cpu)
79{
80	struct vcpu_register_runstate_memory_area area;
81
82	area.addr.v = &per_cpu(xen_runstate, cpu);
83
84	if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
85			       cpu, &area))
86		BUG();
87}
88