spinlock.c 3.47 KB
Newer Older
1
// SPDX-License-Identifier: GPL-2.0
2 3 4 5 6 7
/*
 * Split spinlock implementation out into its own file, so it can be
 * compiled in a FTRACE-compatible way.
 */
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
8 9
#include <linux/debugfs.h>
#include <linux/log2.h>
10
#include <linux/gfp.h>
11
#include <linux/slab.h>
12 13

#include <asm/paravirt.h>
14
#include <asm/qspinlock.h>
15 16 17 18 19

#include <xen/interface/xen.h>
#include <xen/events.h>

#include "xen-ops.h"
20 21
#include "debugfs.h"

22 23 24 25 26 27
static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
static DEFINE_PER_CPU(char *, irq_name);
static bool xen_pvspin = true;

static void xen_qlock_kick(int cpu)
{
28 29 30 31 32 33
	int irq = per_cpu(lock_kicker_irq, cpu);

	/* Don't kick if the target's kicker interrupt is not initialized. */
	if (irq == -1)
		return;

34 35 36 37 38 39 40 41
	xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
}

/*
 * Halt the current CPU & release it back to the host
 */
static void xen_qlock_wait(u8 *byte, u8 val)
{
42
	unsigned long flags;
43 44 45
	int irq = __this_cpu_read(lock_kicker_irq);

	/* If kicker interrupts not initialized yet, just spin */
46
	if (irq == -1 || in_nmi())
47 48
		return;

49 50 51 52
	/* Guard against reentry. */
	local_irq_save(flags);

	/* If irq pending already clear it. */
53 54
	if (xen_test_irq_pending(irq)) {
		xen_clear_irq_pending(irq);
55 56 57
	} else if (READ_ONCE(*byte) == val) {
		/* Block until irq becomes pending (or a spurious wakeup) */
		xen_poll_irq(irq);
58
	}
59

60
	local_irq_restore(flags);
61 62
}

63 64 65 66 67 68
static irqreturn_t dummy_handler(int irq, void *dev_id)
{
	BUG();
	return IRQ_HANDLED;
}

69
void xen_init_lock_cpu(int cpu)
70 71
{
	int irq;
72
	char *name;
73

74 75 76
	if (!xen_pvspin) {
		if (cpu == 0)
			static_branch_disable(&virt_spin_lock_key);
77
		return;
78
	}
79

80
	WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
81 82
	     cpu, per_cpu(lock_kicker_irq, cpu));

83 84 85 86
	name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
	irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
				     cpu,
				     dummy_handler,
87
				     IRQF_PERCPU|IRQF_NOBALANCING,
88 89 90 91 92 93
				     name,
				     NULL);

	if (irq >= 0) {
		disable_irq(irq); /* make sure it's never delivered */
		per_cpu(lock_kicker_irq, cpu) = irq;
94
		per_cpu(irq_name, cpu) = name;
95 96 97 98 99
	}

	printk("cpu %d spinlock event irq %d\n", cpu, irq);
}

Alex Nixon's avatar
Alex Nixon committed
100 101
void xen_uninit_lock_cpu(int cpu)
{
102 103 104
	if (!xen_pvspin)
		return;

Alex Nixon's avatar
Alex Nixon committed
105
	unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
106
	per_cpu(lock_kicker_irq, cpu) = -1;
107 108
	kfree(per_cpu(irq_name, cpu));
	per_cpu(irq_name, cpu) = NULL;
Alex Nixon's avatar
Alex Nixon committed
109 110
}

111 112
PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);

113 114 115 116 117 118 119 120
/*
 * Our init of PV spinlocks is split in two init functions due to us
 * using paravirt patching and jump labels patching and having to do
 * all of this before SMP code is invoked.
 *
 * The paravirt patching needs to be done _before_ the alternative asm code
 * is started, otherwise we would not patch the core kernel code.
 */
121 122
void __init xen_init_spinlocks(void)
{
123

124 125 126 127
	/*  Don't need to use pvqspinlock code if there is only 1 vCPU. */
	if (num_possible_cpus() == 1)
		xen_pvspin = false;

128 129 130 131
	if (!xen_pvspin) {
		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
		return;
	}
132
	printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
133

134
	__pv_init_lock_hash();
135 136 137 138 139 140
	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 = xen_qlock_wait;
	pv_ops.lock.kick = xen_qlock_kick;
	pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
141
}
142

143 144 145 146 147 148 149
static __init int xen_parse_nopvspin(char *arg)
{
	xen_pvspin = false;
	return 0;
}
early_param("xen_nopvspin", xen_parse_nopvspin);