LXR linux/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 */
  22void xen_force_evtchn_callback(void)
  23{
  24        (void)HYPERVISOR_xen_version(0, NULL);
  25}
  26
  27asmlinkage __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}
  43PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  44
  45asmlinkage __visible void xen_irq_disable(void)
  46{
  47        /* There's a one instruction preempt window here.  We need to
  48           make sure we're don't switch CPUs between getting the vcpu
  49           pointer and updating the mask. */
  50        preempt_disable();
  51        this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  52        preempt_enable_no_resched();
  53}
  54PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  55
  56asmlinkage __visible void xen_irq_enable(void)
  57{
  58        struct vcpu_info *vcpu;
  59
  60        /*
  61         * We may be preempted as soon as vcpu->evtchn_upcall_mask is
  62         * cleared, so disable preemption to ensure we check for
  63         * events on the VCPU we are still running on.
  64         */
  65        preempt_disable();
  66
  67        vcpu = this_cpu_read(xen_vcpu);
  68        vcpu->evtchn_upcall_mask = 0;
  69
  70        /* Doesn't matter if we get preempted here, because any
  71           pending event will get dealt with anyway. */
  72
  73        barrier(); /* unmask then check (avoid races) */
  74        if (unlikely(vcpu->evtchn_upcall_pending))
  75                xen_force_evtchn_callback();
  76
  77        preempt_enable();
  78}
  79PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
  80
  81static void xen_safe_halt(void)
  82{
  83        /* Blocking includes an implicit local_irq_enable(). */
  84        if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
  85                BUG();
  86}
  87
  88static void xen_halt(void)
  89{
  90        if (irqs_disabled())
  91                HYPERVISOR_vcpu_op(VCPUOP_down,
  92                                   xen_vcpu_nr(smp_processor_id()), NULL);
  93        else
  94                xen_safe_halt();
  95}
  96
  97static const struct pv_irq_ops xen_irq_ops __initconst = {
  98        .save_fl = PV_CALLEE_SAVE(xen_save_fl),
  99        .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 100        .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 101
 102        .safe_halt = xen_safe_halt,
 103        .halt = xen_halt,
 104};
 105
 106void __init xen_init_irq_ops(void)
 107{
 108        pv_ops.irq = xen_irq_ops;
 109        x86_init.irqs.intr_init = xen_init_IRQ;
 110}
 111