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 */
23static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
24
25static DEFINE_PER_CPU(u64[4], old_runstate_time);
26
27/* return an consistent snapshot of 64-bit time/counter value */
28static 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
55static 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
74static 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
85void 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 */
142void 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 */
148bool xen_vcpu_stolen(int vcpu)
149{
150	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
151}
152
153u64 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
161void 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
172void __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}
185