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
  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}
  65PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  66
  67asmlinkage __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}
  76PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  77
  78asmlinkage __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}
 101PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 102
 103static 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
 110static 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
 119static 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
 129void __init xen_init_irq_ops(void)
 130{
 131        pv_ops.irq = xen_irq_ops;
 132        x86_init.irqs.intr_init = xen_init_IRQ;
 133}
 134