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// SPDX-License-Identifier: GPL-2.0
/*
* Xen stolen ticks accounting.
*/
#include <linux/kernel.h>
#include <linux/kernel_stat.h>
#include <linux/math64.h>
#include <linux/gfp.h>
#include <asm/paravirt.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/events.h>
#include <xen/features.h>
#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>
#include <xen/xen-ops.h>
/* runstate info updated by Xen */
static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
/* return an consistent snapshot of 64-bit time/counter value */
static u64 get64(const u64 *p)
{
u64 ret;
if (BITS_PER_LONG < 64) {
u32 *p32 = (u32 *)p;
u32 h, l, h2;
/*
* Read high then low, and then make sure high is
* still the same; this will only loop if low wraps
* and carries into high.
* XXX some clean way to make this endian-proof?
*/
do {
h = READ_ONCE(p32[1]);
l = READ_ONCE(p32[0]);
h2 = READ_ONCE(p32[1]);
} while(h2 != h);
ret = (((u64)h) << 32) | l;
} else
ret = READ_ONCE(*p);
return ret;
}
static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
unsigned int cpu)
{
u64 state_time;
struct vcpu_runstate_info *state;
BUG_ON(preemptible());
state = per_cpu_ptr(&xen_runstate, cpu);
do {
state_time = get64(&state->state_entry_time);
rmb(); /* Hypervisor might update data. */
*res = READ_ONCE(*state);
rmb(); /* Hypervisor might update data. */
} while (get64(&state->state_entry_time) != state_time ||
(state_time & XEN_RUNSTATE_UPDATE));
}
/*
* Runstate accounting
*/
void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
{
xen_get_runstate_snapshot_cpu(res, smp_processor_id());
}
/* return true when a vcpu could run but has no real cpu to run on */
bool xen_vcpu_stolen(int vcpu)
{
return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
}
u64 xen_steal_clock(int cpu)
{
struct vcpu_runstate_info state;
xen_get_runstate_snapshot_cpu(&state, cpu);
return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
}
void xen_setup_runstate_info(int cpu)
{
struct vcpu_register_runstate_memory_area area;
area.addr.v = &per_cpu(xen_runstate, cpu);
if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
xen_vcpu_nr(cpu), &area))
BUG();
}
void __init xen_time_setup_guest(void)
{
bool xen_runstate_remote;
xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
VMASST_TYPE_runstate_update_flag);
pv_time_ops.steal_clock = xen_steal_clock;
static_key_slow_inc(¶virt_steal_enabled);
if (xen_runstate_remote)
static_key_slow_inc(¶virt_steal_rq_enabled);
}
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