1 // SPDX-License-Identifier: GPL-2.0
3 * Split spinlock implementation out into its own file, so it can be
4 * compiled in a FTRACE-compatible way.
6 #include <linux/kernel_stat.h>
7 #include <linux/spinlock.h>
8 #include <linux/debugfs.h>
9 #include <linux/log2.h>
10 #include <linux/gfp.h>
11 #include <linux/slab.h>
12 #include <linux/atomic.h>
14 #include <asm/paravirt.h>
16 #include <xen/interface/xen.h>
17 #include <xen/events.h>
22 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
23 static DEFINE_PER_CPU(char *, irq_name);
24 static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
25 static bool xen_pvspin = true;
27 #include <asm/qspinlock.h>
29 static void xen_qlock_kick(int cpu)
31 int irq = per_cpu(lock_kicker_irq, cpu);
33 /* Don't kick if the target's kicker interrupt is not initialized. */
37 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
41 * Halt the current CPU & release it back to the host
43 static void xen_qlock_wait(u8 *byte, u8 val)
45 int irq = __this_cpu_read(lock_kicker_irq);
46 atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
48 /* If kicker interrupts not initialized yet, just spin */
49 if (irq == -1 || in_nmi())
55 /* If irq pending already and no nested call clear it. */
56 if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
57 xen_clear_irq_pending(irq);
58 } else if (READ_ONCE(*byte) == val) {
59 /* Block until irq becomes pending (or a spurious wakeup) */
66 static irqreturn_t dummy_handler(int irq, void *dev_id)
72 void xen_init_lock_cpu(int cpu)
80 WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
81 cpu, per_cpu(lock_kicker_irq, cpu));
83 name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
84 irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
87 IRQF_PERCPU|IRQF_NOBALANCING,
92 disable_irq(irq); /* make sure it's never delivered */
93 per_cpu(lock_kicker_irq, cpu) = irq;
94 per_cpu(irq_name, cpu) = name;
97 printk("cpu %d spinlock event irq %d\n", cpu, irq);
100 void xen_uninit_lock_cpu(int cpu)
108 * When booting the kernel with 'mitigations=auto,nosmt', the secondary
109 * CPUs are not activated, and lock_kicker_irq is not initialized.
111 irq = per_cpu(lock_kicker_irq, cpu);
115 unbind_from_irqhandler(irq, NULL);
116 per_cpu(lock_kicker_irq, cpu) = -1;
117 kfree(per_cpu(irq_name, cpu));
118 per_cpu(irq_name, cpu) = NULL;
121 PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
124 * Our init of PV spinlocks is split in two init functions due to us
125 * using paravirt patching and jump labels patching and having to do
126 * all of this before SMP code is invoked.
128 * The paravirt patching needs to be done _before_ the alternative asm code
129 * is started, otherwise we would not patch the core kernel code.
131 void __init xen_init_spinlocks(void)
135 printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
138 printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
140 __pv_init_lock_hash();
141 pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
142 pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
143 pv_lock_ops.wait = xen_qlock_wait;
144 pv_lock_ops.kick = xen_qlock_kick;
145 pv_lock_ops.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
148 static __init int xen_parse_nopvspin(char *arg)
153 early_param("xen_nopvspin", xen_parse_nopvspin);