2 * Split spinlock implementation out into its own file, so it can be
3 * compiled in a FTRACE-compatible way.
5 #include <linux/kernel_stat.h>
6 #include <linux/spinlock.h>
7 #include <linux/debugfs.h>
8 #include <linux/log2.h>
10 #include <linux/slab.h>
11 #include <linux/atomic.h>
13 #include <asm/paravirt.h>
15 #include <xen/interface/xen.h>
16 #include <xen/events.h>
21 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
22 static DEFINE_PER_CPU(char *, irq_name);
23 static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
24 static bool xen_pvspin = true;
26 #include <asm/qspinlock.h>
28 static void xen_qlock_kick(int cpu)
30 int irq = per_cpu(lock_kicker_irq, cpu);
32 /* Don't kick if the target's kicker interrupt is not initialized. */
36 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
40 * Halt the current CPU & release it back to the host
42 static void xen_qlock_wait(u8 *byte, u8 val)
44 int irq = __this_cpu_read(lock_kicker_irq);
45 atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
47 /* If kicker interrupts not initialized yet, just spin */
48 if (irq == -1 || in_nmi())
54 /* If irq pending already and no nested call clear it. */
55 if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
56 xen_clear_irq_pending(irq);
57 } else if (READ_ONCE(*byte) == val) {
58 /* Block until irq becomes pending (or a spurious wakeup) */
65 static irqreturn_t dummy_handler(int irq, void *dev_id)
71 void xen_init_lock_cpu(int cpu)
79 WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
80 cpu, per_cpu(lock_kicker_irq, cpu));
82 name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
83 irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
86 IRQF_PERCPU|IRQF_NOBALANCING,
91 disable_irq(irq); /* make sure it's never delivered */
92 per_cpu(lock_kicker_irq, cpu) = irq;
93 per_cpu(irq_name, cpu) = name;
96 printk("cpu %d spinlock event irq %d\n", cpu, irq);
99 void xen_uninit_lock_cpu(int cpu)
107 * When booting the kernel with 'mitigations=auto,nosmt', the secondary
108 * CPUs are not activated, and lock_kicker_irq is not initialized.
110 irq = per_cpu(lock_kicker_irq, cpu);
114 unbind_from_irqhandler(irq, NULL);
115 per_cpu(lock_kicker_irq, cpu) = -1;
116 kfree(per_cpu(irq_name, cpu));
117 per_cpu(irq_name, cpu) = NULL;
122 * Our init of PV spinlocks is split in two init functions due to us
123 * using paravirt patching and jump labels patching and having to do
124 * all of this before SMP code is invoked.
126 * The paravirt patching needs to be done _before_ the alternative asm code
127 * is started, otherwise we would not patch the core kernel code.
129 void __init xen_init_spinlocks(void)
133 printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
136 printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
138 __pv_init_lock_hash();
139 pv_lock_ops.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
140 pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
141 pv_lock_ops.wait = xen_qlock_wait;
142 pv_lock_ops.kick = xen_qlock_kick;
146 * While the jump_label init code needs to happend _after_ the jump labels are
147 * enabled and before SMP is started. Hence we use pre-SMP initcall level
148 * init. We cannot do it in xen_init_spinlocks as that is done before
149 * jump labels are activated.
151 static __init int xen_init_spinlocks_jump(void)
159 static_key_slow_inc(¶virt_ticketlocks_enabled);
162 early_initcall(xen_init_spinlocks_jump);
164 static __init int xen_parse_nopvspin(char *arg)
169 early_param("xen_nopvspin", xen_parse_nopvspin);