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