LXR linux/arch/x86/xen/irq.c

   1#include <linux/hardirq.h>
   2
   3#include <asm/x86_init.h>
   4
   5#include <xen/interface/xen.h>
   6#include <xen/interface/sched.h>
   7#include <xen/interface/vcpu.h>
   8
   9#include <asm/xen/hypercall.h>
  10#include <asm/xen/hypervisor.h>
  11
  12#include "xen-ops.h"
  13
  14/*
  15 * Force a proper event-channel callback from Xen after clearing the
  16 * callback mask. We do this in a very simple manner, by making a call
  17 * down into Xen. The pending flag will be checked by Xen on return.
  18 */
  19void xen_force_evtchn_callback(void)
  20{
  21        (void)HYPERVISOR_xen_version(0, NULL);
  22}
  23
  24static unsigned long xen_save_fl(void)
  25{
  26        struct vcpu_info *vcpu;
  27        unsigned long flags;
  28
  29        vcpu = percpu_read(xen_vcpu);
  30
  31        /* flag has opposite sense of mask */
  32        flags = !vcpu->evtchn_upcall_mask;
  33
  34        /* convert to IF type flag
  35           -0 -> 0x00000000
  36           -1 -> 0xffffffff
  37        */
  38        return (-flags) & X86_EFLAGS_IF;
  39}
  40PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);
  41
  42static void xen_restore_fl(unsigned long flags)
  43{
  44        struct vcpu_info *vcpu;
  45
  46        /* convert from IF type flag */
  47        flags = !(flags & X86_EFLAGS_IF);
  48
  49        /* There's a one instruction preempt window here.  We need to
  50           make sure we're don't switch CPUs between getting the vcpu
  51           pointer and updating the mask. */
  52        preempt_disable();
  53        vcpu = percpu_read(xen_vcpu);
  54        vcpu->evtchn_upcall_mask = flags;
  55        preempt_enable_no_resched();
  56
  57        /* Doesn't matter if we get preempted here, because any
  58           pending event will get dealt with anyway. */
  59
  60        if (flags == 0) {
  61                preempt_check_resched();
  62                barrier(); /* unmask then check (avoid races) */
  63                if (unlikely(vcpu->evtchn_upcall_pending))
  64                        xen_force_evtchn_callback();
  65        }
  66}
  67PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);
  68
  69static void xen_irq_disable(void)
  70{
  71        /* There's a one instruction preempt window here.  We need to
  72           make sure we're don't switch CPUs between getting the vcpu
  73           pointer and updating the mask. */
  74        preempt_disable();
  75        percpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
  76        preempt_enable_no_resched();
  77}
  78PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);
  79
  80static void xen_irq_enable(void)
  81{
  82        struct vcpu_info *vcpu;
  83
  84        /* We don't need to worry about being preempted here, since
  85           either a) interrupts are disabled, so no preemption, or b)
  86           the caller is confused and is trying to re-enable interrupts
  87           on an indeterminate processor. */
  88
  89        vcpu = percpu_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}
  99PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);
 100
 101static void xen_safe_halt(void)
 102{
 103        /* Blocking includes an implicit local_irq_enable(). */
 104        if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
 105                BUG();
 106}
 107
 108static void xen_halt(void)
 109{
 110        if (irqs_disabled())
 111                HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
 112        else
 113                xen_safe_halt();
 114}
 115
 116static const struct pv_irq_ops xen_irq_ops __initdata = {
 117        .save_fl = PV_CALLEE_SAVE(xen_save_fl),
 118        .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
 119        .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
 120        .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),
 121
 122        .safe_halt = xen_safe_halt,
 123        .halt = xen_halt,
 124#ifdef CONFIG_X86_64
 125        .adjust_exception_frame = xen_adjust_exception_frame,
 126#endif
 127};
 128
 129void __init xen_init_irq_ops()
 130{
 131        pv_irq_ops = xen_irq_ops;
 132        x86_init.irqs.intr_init = xen_init_IRQ;
 133}
 134