93 lines
2.2 KiB
C
93 lines
2.2 KiB
C
// 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 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) {
|
|
unsigned long msr_val;
|
|
|
|
rdmsrl(HV_X64_MSR_GUEST_IDLE, msr_val);
|
|
|
|
(void)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);
|