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 */
 20static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
 21
 22/* return an consistent snapshot of 64-bit time/counter value */
 23static 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
 50static 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 */
 72void 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 */
 78bool xen_vcpu_stolen(int vcpu)
 79{
 80	return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
 81}
 82
 83u64 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
 91void 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
102void __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(&paravirt_steal_enabled);
112	if (xen_runstate_remote)
113		static_key_slow_inc(&paravirt_steal_rq_enabled);
114}