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
)
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)
125 printk(KERN_DEBUG
"xen: PV spinlocks disabled\n");
128 printk(KERN_DEBUG
"xen: PV spinlocks enabled\n");
130 __pv_init_lock_hash();
131 pv_lock_ops
.queued_spin_lock_slowpath
= __pv_queued_spin_lock_slowpath
;
132 pv_lock_ops
.queued_spin_unlock
= PV_CALLEE_SAVE(__pv_queued_spin_unlock
);
133 pv_lock_ops
.wait
= xen_qlock_wait
;
134 pv_lock_ops
.kick
= xen_qlock_kick
;
135 pv_lock_ops
.vcpu_is_preempted
= PV_CALLEE_SAVE(xen_vcpu_stolen
);
138 static __init
int xen_parse_nopvspin(char *arg
)
143 early_param("xen_nopvspin", xen_parse_nopvspin
);