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 */
 22static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
 23
 24static DEFINE_PER_CPU(u64[4], old_runstate_time);
 25
 26/* return an consistent snapshot of 64-bit time/counter value */
 27static 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
 54static 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
 73static 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
 84void 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 */
141void 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 */
147bool xen_vcpu_stolen(int vcpu)
148{
149	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
150}
151
152u64 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
160void 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
171void __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_ops.time.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}