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_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 13 #include <asm/paravirt.h> 14 #include <asm/qspinlock.h> 15 16 #include <xen/interface/xen.h> 17 #include <xen/events.h> 18 19 #include "xen-ops.h" 20 #include "debugfs.h" 21 22 static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; 23 static DEFINE_PER_CPU(char *, irq_name); 24 static bool xen_pvspin = true; 25 26 static void xen_qlock_kick(int cpu) 27 { 28 int irq = per_cpu(lock_kicker_irq, cpu); 29 30 /* Don't kick if the target's kicker interrupt is not initialized. */ 31 if (irq == -1) 32 return; 33 34 xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR); 35 } 36 37 /* 38 * Halt the current CPU & release it back to the host 39 */ 40 static void xen_qlock_wait(u8 *byte, u8 val) 41 { 42 unsigned long flags; 43 int irq = __this_cpu_read(lock_kicker_irq); 44 45 /* If kicker interrupts not initialized yet, just spin */ 46 if (irq == -1 || in_nmi()) 47 return; 48 49 /* Guard against reentry. */ 50 local_irq_save(flags); 51 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) */ 57 xen_poll_irq(irq); 58 } 59 60 local_irq_restore(flags); 61 } 62 63 static irqreturn_t dummy_handler(int irq, void *dev_id) 64 { 65 BUG(); 66 return IRQ_HANDLED; 67 } 68 69 void xen_init_lock_cpu(int cpu) 70 { 71 int irq; 72 char *name; 73 74 if (!xen_pvspin) { 75 if (cpu == 0) 76 static_branch_disable(&virt_spin_lock_key); 77 return; 78 } 79 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)); 82 83 name = kasprintf(GFP_KERNEL, "spinlock%d", cpu); 84 irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR, 85 cpu, 86 dummy_handler, 87 IRQF_PERCPU|IRQF_NOBALANCING, 88 name, 89 NULL); 90 91 if (irq >= 0) { 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; 95 } 96 97 printk("cpu %d spinlock event irq %d\n", cpu, irq); 98 } 99 100 void xen_uninit_lock_cpu(int cpu) 101 { 102 if (!xen_pvspin) 103 return; 104 105 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; 109 } 110 111 PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen); 112 113 /* 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. 117 * 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. 120 */ 121 void __init xen_init_spinlocks(void) 122 { 123 124 /* Don't need to use pvqspinlock code if there is only 1 vCPU. */ 125 if (num_possible_cpus() == 1) 126 xen_pvspin = false; 127 128 if (!xen_pvspin) { 129 printk(KERN_DEBUG "xen: PV spinlocks disabled\n"); 130 return; 131 } 132 printk(KERN_DEBUG "xen: PV spinlocks enabled\n"); 133 134 __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); 141 } 142 143 static __init int xen_parse_nopvspin(char *arg) 144 { 145 xen_pvspin = false; 146 return 0; 147 } 148 early_param("xen_nopvspin", xen_parse_nopvspin); 149 150