irq.c

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#include <linux/hardirq.h>

#include <asm/x86_init.h>

#include <xen/interface/xen.h>
#include <xen/interface/sched.h>
#include <xen/interface/vcpu.h>
#include <xen/events.h>

#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

#include "xen-ops.h"

/*
 * Force a proper event-channel callback from Xen after clearing the
 * callback mask. We do this in a very simple manner, by making a call
 * down into Xen. The pending flag will be checked by Xen on return.
 */
void xen_force_evtchn_callback(void)
{
    (void)HYPERVISOR_xen_version(0, NULL);
}

static unsigned long xen_save_fl(void)
{
    struct vcpu_info *vcpu;
    unsigned long flags;

    vcpu = this_cpu_read(xen_vcpu);

    /* flag has opposite sense of mask */
    flags = !vcpu->evtchn_upcall_mask;

    /* convert to IF type flag
       -0 -> 0x00000000
       -1 -> 0xffffffff
    */
    return (-flags) & X86_EFLAGS_IF;
}
PV_CALLEE_SAVE_REGS_THUNK(xen_save_fl);

static void xen_restore_fl(unsigned long flags)
{
    struct vcpu_info *vcpu;

    /* convert from IF type flag */
    flags = !(flags & X86_EFLAGS_IF);

    /* There's a one instruction preempt window here.  We need to
       make sure we're don't switch CPUs between getting the vcpu
       pointer and updating the mask. */
    preempt_disable();
    vcpu = this_cpu_read(xen_vcpu);
    vcpu->evtchn_upcall_mask = flags;
    preempt_enable_no_resched();

    /* Doesn't matter if we get preempted here, because any
       pending event will get dealt with anyway. */

    if (flags == 0) {
        preempt_check_resched();
        barrier(); /* unmask then check (avoid races) */
        if (unlikely(vcpu->evtchn_upcall_pending))
            xen_force_evtchn_callback();
    }
}
PV_CALLEE_SAVE_REGS_THUNK(xen_restore_fl);

static void xen_irq_disable(void)
{
    /* There's a one instruction preempt window here.  We need to
       make sure we're don't switch CPUs between getting the vcpu
       pointer and updating the mask. */
    preempt_disable();
    this_cpu_read(xen_vcpu)->evtchn_upcall_mask = 1;
    preempt_enable_no_resched();
}
PV_CALLEE_SAVE_REGS_THUNK(xen_irq_disable);

static void xen_irq_enable(void)
{
    struct vcpu_info *vcpu;

    /* We don't need to worry about being preempted here, since
       either a) interrupts are disabled, so no preemption, or b)
       the caller is confused and is trying to re-enable interrupts
       on an indeterminate processor. */

    vcpu = this_cpu_read(xen_vcpu);
    vcpu->evtchn_upcall_mask = 0;

    /* Doesn't matter if we get preempted here, because any
       pending event will get dealt with anyway. */

    barrier(); /* unmask then check (avoid races) */
    if (unlikely(vcpu->evtchn_upcall_pending))
        xen_force_evtchn_callback();
}
PV_CALLEE_SAVE_REGS_THUNK(xen_irq_enable);

static void xen_safe_halt(void)
{
    /* Blocking includes an implicit local_irq_enable(). */
    if (HYPERVISOR_sched_op(SCHEDOP_block, NULL) != 0)
        BUG();
}

static void xen_halt(void)
{
    if (irqs_disabled())
        HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
    else
        xen_safe_halt();
}

static const struct pv_irq_ops xen_irq_ops __initconst = {
    .save_fl = PV_CALLEE_SAVE(xen_save_fl),
    .restore_fl = PV_CALLEE_SAVE(xen_restore_fl),
    .irq_disable = PV_CALLEE_SAVE(xen_irq_disable),
    .irq_enable = PV_CALLEE_SAVE(xen_irq_enable),

    .safe_halt = xen_safe_halt,
    .halt = xen_halt,
#ifdef CONFIG_X86_64
    .adjust_exception_frame = xen_adjust_exception_frame,
#endif
};

void __init xen_init_irq_ops(void)
{
    pv_irq_ops = xen_irq_ops;
    x86_init.irqs.intr_init = xen_init_IRQ;
}