Loading...
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Split spinlock implementation out into its own file, so it can be
4 * compiled in a FTRACE-compatible way.
5 */
6#include <linux/kernel.h>
7#include <linux/spinlock.h>
8#include <linux/slab.h>
9#include <linux/atomic.h>
10
11#include <asm/paravirt.h>
12#include <asm/qspinlock.h>
13
14#include <xen/events.h>
15
16#include "xen-ops.h"
17
18static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
19static DEFINE_PER_CPU(char *, irq_name);
20static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
21static bool xen_pvspin = true;
22
23static void xen_qlock_kick(int cpu)
24{
25 int irq = per_cpu(lock_kicker_irq, cpu);
26
27 /* Don't kick if the target's kicker interrupt is not initialized. */
28 if (irq == -1)
29 return;
30
31 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
32}
33
34/*
35 * Halt the current CPU & release it back to the host
36 */
37static void xen_qlock_wait(u8 *byte, u8 val)
38{
39 int irq = __this_cpu_read(lock_kicker_irq);
40 atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
41
42 /* If kicker interrupts not initialized yet, just spin */
43 if (irq == -1 || in_nmi())
44 return;
45
46 /* Detect reentry. */
47 atomic_inc(nest_cnt);
48
49 /* If irq pending already and no nested call clear it. */
50 if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
51 xen_clear_irq_pending(irq);
52 } else if (READ_ONCE(*byte) == val) {
53 /* Block until irq becomes pending (or a spurious wakeup) */
54 xen_poll_irq(irq);
55 }
56
57 atomic_dec(nest_cnt);
58}
59
60static irqreturn_t dummy_handler(int irq, void *dev_id)
61{
62 BUG();
63 return IRQ_HANDLED;
64}
65
66void xen_init_lock_cpu(int cpu)
67{
68 int irq;
69 char *name;
70
71 if (!xen_pvspin)
72 return;
73
74 WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
75 cpu, per_cpu(lock_kicker_irq, cpu));
76
77 name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
78 per_cpu(irq_name, cpu) = name;
79 irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
80 cpu,
81 dummy_handler,
82 IRQF_PERCPU|IRQF_NOBALANCING,
83 name,
84 NULL);
85
86 if (irq >= 0) {
87 disable_irq(irq); /* make sure it's never delivered */
88 per_cpu(lock_kicker_irq, cpu) = irq;
89 }
90
91 printk("cpu %d spinlock event irq %d\n", cpu, irq);
92}
93
94void xen_uninit_lock_cpu(int cpu)
95{
96 int irq;
97
98 if (!xen_pvspin)
99 return;
100
101 kfree(per_cpu(irq_name, cpu));
102 per_cpu(irq_name, cpu) = NULL;
103 /*
104 * When booting the kernel with 'mitigations=auto,nosmt', the secondary
105 * CPUs are not activated, and lock_kicker_irq is not initialized.
106 */
107 irq = per_cpu(lock_kicker_irq, cpu);
108 if (irq == -1)
109 return;
110
111 unbind_from_irqhandler(irq, NULL);
112 per_cpu(lock_kicker_irq, cpu) = -1;
113}
114
115PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
116
117/*
118 * Our init of PV spinlocks is split in two init functions due to us
119 * using paravirt patching and jump labels patching and having to do
120 * all of this before SMP code is invoked.
121 *
122 * The paravirt patching needs to be done _before_ the alternative asm code
123 * is started, otherwise we would not patch the core kernel code.
124 */
125void __init xen_init_spinlocks(void)
126{
127 /* Don't need to use pvqspinlock code if there is only 1 vCPU. */
128 if (num_possible_cpus() == 1 || nopvspin)
129 xen_pvspin = false;
130
131 if (!xen_pvspin) {
132 printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
133 static_branch_disable(&virt_spin_lock_key);
134 return;
135 }
136 printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
137
138 __pv_init_lock_hash();
139 pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
140 pv_ops.lock.queued_spin_unlock =
141 PV_CALLEE_SAVE(__pv_queued_spin_unlock);
142 pv_ops.lock.wait = xen_qlock_wait;
143 pv_ops.lock.kick = xen_qlock_kick;
144 pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
145}
146
147static __init int xen_parse_nopvspin(char *arg)
148{
149 pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
150 xen_pvspin = false;
151 return 0;
152}
153early_param("xen_nopvspin", xen_parse_nopvspin);
154
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Split spinlock implementation out into its own file, so it can be
4 * compiled in a FTRACE-compatible way.
5 */
6#include <linux/kernel.h>
7#include <linux/spinlock.h>
8#include <linux/slab.h>
9#include <linux/atomic.h>
10
11#include <asm/paravirt.h>
12#include <asm/qspinlock.h>
13
14#include <xen/events.h>
15
16#include "xen-ops.h"
17
18static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
19static DEFINE_PER_CPU(char *, irq_name);
20static DEFINE_PER_CPU(atomic_t, xen_qlock_wait_nest);
21static bool xen_pvspin = true;
22
23static void xen_qlock_kick(int cpu)
24{
25 int irq = per_cpu(lock_kicker_irq, cpu);
26
27 /* Don't kick if the target's kicker interrupt is not initialized. */
28 if (irq == -1)
29 return;
30
31 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
32}
33
34/*
35 * Halt the current CPU & release it back to the host
36 */
37static void xen_qlock_wait(u8 *byte, u8 val)
38{
39 int irq = __this_cpu_read(lock_kicker_irq);
40 atomic_t *nest_cnt = this_cpu_ptr(&xen_qlock_wait_nest);
41
42 /* If kicker interrupts not initialized yet, just spin */
43 if (irq == -1 || in_nmi())
44 return;
45
46 /* Detect reentry. */
47 atomic_inc(nest_cnt);
48
49 /* If irq pending already and no nested call clear it. */
50 if (atomic_read(nest_cnt) == 1 && xen_test_irq_pending(irq)) {
51 xen_clear_irq_pending(irq);
52 } else if (READ_ONCE(*byte) == val) {
53 /* Block until irq becomes pending (or a spurious wakeup) */
54 xen_poll_irq(irq);
55 }
56
57 atomic_dec(nest_cnt);
58}
59
60static irqreturn_t dummy_handler(int irq, void *dev_id)
61{
62 BUG();
63 return IRQ_HANDLED;
64}
65
66void xen_init_lock_cpu(int cpu)
67{
68 int irq;
69 char *name;
70
71 if (!xen_pvspin)
72 return;
73
74 WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n",
75 cpu, per_cpu(lock_kicker_irq, cpu));
76
77 name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
78 irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
79 cpu,
80 dummy_handler,
81 IRQF_PERCPU|IRQF_NOBALANCING,
82 name,
83 NULL);
84
85 if (irq >= 0) {
86 disable_irq(irq); /* make sure it's never delivered */
87 per_cpu(lock_kicker_irq, cpu) = irq;
88 per_cpu(irq_name, cpu) = name;
89 }
90
91 printk("cpu %d spinlock event irq %d\n", cpu, irq);
92}
93
94void xen_uninit_lock_cpu(int cpu)
95{
96 if (!xen_pvspin)
97 return;
98
99 unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL);
100 per_cpu(lock_kicker_irq, cpu) = -1;
101 kfree(per_cpu(irq_name, cpu));
102 per_cpu(irq_name, cpu) = NULL;
103}
104
105PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
106
107/*
108 * Our init of PV spinlocks is split in two init functions due to us
109 * using paravirt patching and jump labels patching and having to do
110 * all of this before SMP code is invoked.
111 *
112 * The paravirt patching needs to be done _before_ the alternative asm code
113 * is started, otherwise we would not patch the core kernel code.
114 */
115void __init xen_init_spinlocks(void)
116{
117 /* Don't need to use pvqspinlock code if there is only 1 vCPU. */
118 if (num_possible_cpus() == 1 || nopvspin)
119 xen_pvspin = false;
120
121 if (!xen_pvspin) {
122 printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
123 static_branch_disable(&virt_spin_lock_key);
124 return;
125 }
126 printk(KERN_DEBUG "xen: PV spinlocks enabled\n");
127
128 __pv_init_lock_hash();
129 pv_ops.lock.queued_spin_lock_slowpath = __pv_queued_spin_lock_slowpath;
130 pv_ops.lock.queued_spin_unlock =
131 PV_CALLEE_SAVE(__pv_queued_spin_unlock);
132 pv_ops.lock.wait = xen_qlock_wait;
133 pv_ops.lock.kick = xen_qlock_kick;
134 pv_ops.lock.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
135}
136
137static __init int xen_parse_nopvspin(char *arg)
138{
139 pr_notice("\"xen_nopvspin\" is deprecated, please use \"nopvspin\" instead\n");
140 xen_pvspin = false;
141 return 0;
142}
143early_param("xen_nopvspin", xen_parse_nopvspin);
144