arch/x86/xen/irq.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/hardirq.h>
   3
   4 #include <asm/x86_init.h>
   5
   6 #include <xen/interface/xen.h>
   7 #include <xen/interface/sched.h>
   8 #include <xen/interface/vcpu.h>
   9 #include <xen/features.h>
  10 #include <xen/events.h>
  11
  12 #include <asm/xen/hypercall.h>
  13 #include <asm/xen/hypervisor.h>
  14
  15 #include "xen-ops.h"
  16
  17 /*
  18  * Force a proper event-channel callback from Xen after clearing the
  19  * callback mask. We do this in a very simple manner, by making a call
  20  * down into Xen. The pending flag will be checked by Xen on return.
  21  */
  22 void xen_force_evtchn_callback(void)
  23 {
  24         (void)HYPERVISOR_xen_version(0, NULL);
  25 }
  26
  27 asmlinkage __visible unsigned long xen_save_fl(void)
  28 {
  29         struct vcpu_info *vcpu;
  30         unsigned long flags;
  31
  32         vcpu = this_cpu_read(xen_vcpu);
  33
  34         /* flag has opposite sense of mask */
  35         flags = !vcpu->evtchn_upcall_mask;
  36
  37         /* convert to IF type flag
  38            -0 -> 0x00000000
  39            -1 -> 0xffffffff
  40         */
  41         return (-flags) & X86_EFLAGS_IF;
  42 }
  43 PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  44
  45 __visible void xen_restore_fl(unsigned long flags)
  46 {
  47         struct vcpu_info *vcpu;
  48
  49         /* convert from IF type flag */
  50         flags = !(flags & X86_EFLAGS_IF);
  51
  52         /* See xen_irq_enable() for why preemption must be disabled. */
  53         preempt_disable();
  54         vcpu = this_cpu_read(xen_vcpu);
  55         vcpu->evtchn_upcall_mask = flags;
  56
  57         if (flags == 0) {
  58                 barrier(); /* unmask then check (avoid races) */
  59                 if (unlikely(vcpu->evtchn_upcall_pending))
  60                         xen_force_evtchn_callback();
  61                 preempt_enable();
  62         } else
  63                 preempt_enable_no_resched();
  64 }
  65 PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  66
  67 asmlinkage __visible void xen_irq_disable(void)
  68 {
  69         /* There's a one instruction preempt window here.  We need to
  70            make sure we're don't switch CPUs between getting the vcpu
  71            pointer and updating the mask. */
  72         preempt_disable();
  73         this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  74         preempt_enable_no_resched();
  75 }
  76 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  77
  78 asmlinkage __visible void xen_irq_enable(void)
  79 {
  80         struct vcpu_info *vcpu;
  81
  82         /*
  83          * We may be preempted as soon as vcpu->evtchn_upcall_mask is
  84          * cleared, so disable preemption to ensure we check for
  85          * events on the VCPU we are still running on.
  86          */
  87         preempt_disable();
  88
  89         vcpu = this_cpu_read(xen_vcpu);
  90         vcpu->evtchn_upcall_mask = 0;
  91
  92         /* Doesn't matter if we get preempted here, because any
  93            pending event will get dealt with anyway. */
  94
  95         barrier(); /* unmask then check (avoid races) */
  96         if (unlikely(vcpu->evtchn_upcall_pending))
  97                 xen_force_evtchn_callback();
  98
  99         preempt_enable();
 100 }
 101 PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 102
 103 static void xen_safe_halt(void)
 104 {
 105         /* Blocking includes an implicit local_irq_enable(). */
 106         if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 107                 BUG();
 108 }
 109
 110 static void xen_halt(void)
 111 {
 112         if (irqs_disabled())
 113                 HYPERVISOR_vcpu_op(VCPUOP_down,
 114                                    xen_vcpu_nr(smp_processor_id()), NULL);
 115         else
 116                 xen_safe_halt();
 117 }
 118
 119 static const struct pv_irq_ops xen_irq_ops __initconst = {
 120         .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 121         .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 122         .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 123         .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 124
 125         .safe_halt = xen_safe_halt,
 126         .halt = xen_halt,
 127 };
 128
 129 void __init xen_init_irq_ops(void)
 130 {
 131         /* For PVH we use default pv_irq_ops settings. */
 132         if (!xen_feature(XENFEAT_hvm_callback_vector))
 133                 pv_irq_ops = xen_irq_ops;
 134         x86_init.irqs.intr_init = xen_init_IRQ;
 135 }