Orange Pi5 kernel

// SPDX-License-Identifier: GPL-2.0
 
/*
 * Hyper-V specific spinlock code.
 *
 * Copyright (C) 2018, Intel, Inc.
 *
 * Author : Yi Sun <yi.y.sun@intel.com>
 */
 
#define pr_fmt(fmt) "Hyper-V: " fmt
 
#include <linux/spinlock.h>
 
#include <asm/mshyperv.h>
#include <asm/paravirt.h>
#include <asm/apic.h>
 
static bool __initdata hv_pvspin = true;
 
static void hv_qlock_kick(int cpu)
{
<------>apic->send_IPI(cpu, X86_PLATFORM_IPI_VECTOR);
}
 
static void hv_qlock_wait(u8 *byte, u8 val)
{
<------>unsigned long msr_val;
<------>unsigned long flags;
 
<------>if (in_nmi())
<------><------>return;
 
<------>/*
<------> * Reading HV_X64_MSR_GUEST_IDLE MSR tells the hypervisor that the
<------> * vCPU can be put into 'idle' state. This 'idle' state is
<------> * terminated by an IPI, usually from hv_qlock_kick(), even if
<------> * interrupts are disabled on the vCPU.
<------> *
<------> * To prevent a race against the unlock path it is required to
<------> * disable interrupts before accessing the HV_X64_MSR_GUEST_IDLE
<------> * MSR. Otherwise, if the IPI from hv_qlock_kick() arrives between
<------> * the lock value check and the rdmsrl() then the vCPU might be put
<------> * into 'idle' state by the hypervisor and kept in that state for
<------> * an unspecified amount of time.
<------> */
<------>local_irq_save(flags);
<------>/*
<------> * Only issue the rdmsrl() when the lock state has not changed.
<------> */
<------>if (READ_ONCE(*byte) == val)
<------><------>rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val);
<------>local_irq_restore(flags);
}
 
/*
 * Hyper-V does not support this so far.
 */
__visible bool hv_vcpu_is_preempted(int vcpu)
{
<------>return false;
}
PV_CALLEE_SAVE_REGS_THUNK(hv_vcpu_is_preempted);
 
void __init hv_init_spinlocks(void)
{
<------>if (!hv_pvspin || !apic ||
<------>    !(ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) ||
<------>    !(ms_hyperv.features & HV_MSR_GUEST_IDLE_AVAILABLE)) {
<------><------>pr_info("PV spinlocks disabled\n");
<------><------>return;
<------>}
<------>pr_info("PV spinlocks enabled\n");
 
<------>__pv_init_lock_hash();
<------>pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
<------>pv_ops.lock.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
<------>pv_ops.lock.wait = hv_qlock_wait;
<------>pv_ops.lock.kick = hv_qlock_kick;
<------>pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(hv_vcpu_is_preempted);
}
 
static __init int hv_parse_nopvspin(char *arg)
{
<------>hv_pvspin = false;
<------>return 0;
}
early_param("hv_nopvspin", hv_parse_nopvspin);