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>
13 #include <asm/paravirt.h>
14 #include <asm/qspinlock.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 bool xen_pvspin = true;
26 static void xen_qlock_kick(int cpu)
28 int irq = per_cpu(lock_kicker_irq, cpu);
30 /* Don't kick if the target's kicker interrupt is not initialized. */
34 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
38 * Halt the current CPU & release it back to the host
40 static void xen_qlock_wait(u8 *byte, u8 val)
43 int irq = __this_cpu_read(lock_kicker_irq);
45 /* If kicker interrupts not initialized yet, just spin */
46 if (irq == -1 || in_nmi())
49 /* Guard against reentry. */
50 local_irq_save(flags);
52 /* If irq pending already clear it. */
53 if (xen_test_irq_pending(irq)) {
54 xen_clear_irq_pending(irq);
55 } else if (READ_ONCE(*byte) == val) {
56 /* Block until irq becomes pending (or a spurious wakeup) */
60 local_irq_restore(flags);
63 static irqreturn_t dummy_handler(int irq, void *dev_id)
69 void xen_init_lock_cpu(int cpu)
76 static_branch_disable(&virt_spin_lock_key);
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)
105 unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
106 per_cpu(lock_kicker_irq, cpu) = -1;
107 kfree(per_cpu(irq_name, cpu));
108 per_cpu(irq_name, cpu) = NULL;
111 PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
114 * Our init of PV spinlocks is split in two init functions due to us
115 * using paravirt patching and jump labels patching and having to do
116 * all of this before SMP code is invoked.
118 * The paravirt patching needs to be done _before_ the alternative asm code
119 * is started, otherwise we would not patch the core kernel code.
121 void __init xen_init_spinlocks(void)
124 /* Don't need to use pvqspinlock code if there is only 1 vCPU. */
125 if (num_possible_cpus() == 1)
129 printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
132 printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
134 __pv_init_lock_hash();
135 pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
136 pv_ops.lock.queued_spin_unlock =
137 PV_CALLEE_SAVE(__pv_queued_spin_unlock);
138 pv_ops.lock.wait = xen_qlock_wait;
139 pv_ops.lock.kick = xen_qlock_kick;
140 pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
143 static __init int xen_parse_nopvspin(char *arg)
148 early_param("xen_nopvspin", xen_parse_nopvspin);