xen: implement pirq type event channels

[linux-2.6.git] / drivers / xen / events.c

/*
 * Xen event channels
 *
 * Xen models interrupts with abstract event channels.  Because each
 * domain gets 1024 event channels, but NR_IRQ is not that large, we
 * must dynamically map irqs<->event channels.  The event channels
 * interface with the rest of the kernel by defining a xen interrupt
 * chip.  When an event is recieved, it is mapped to an irq and sent
 * through the normal interrupt processing path.
 *
 * There are four kinds of events which can be mapped to an event
 * channel:
 *
 * 1. Inter-domain notifications.  This includes all the virtual
 *    device events, since they're driven by front-ends in another domain
 *    (typically dom0).
 * 2. VIRQs, typically used for timers.  These are per-cpu events.
 * 3. IPIs.
 * 4. PIRQs - Hardware interrupts.
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */

#include <linux/linkage.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/bootmem.h>
#include <linux/slab.h>

#include <asm/desc.h>
#include <asm/ptrace.h>
#include <asm/irq.h>
#include <asm/idle.h>
#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/hvm.h>
#include <xen/xen-ops.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>
#include <xen/interface/hvm/hvm_op.h>
#include <xen/interface/hvm/params.h>

/* Leave low irqs free for identity mapping */
#define LEGACY_IRQS     16

/*
 * This lock protects updates to the following mapping and reference-count
 * arrays. The lock does not need to be acquired to read the mapping tables.
 */
static DEFINE_SPINLOCK(irq_mapping_update_lock);

/* IRQ <-> VIRQ mapping. */
static DEFINE_PER_CPU(int [NR_VIRQS], virq_to_irq) = {[0 ... NR_VIRQS-1] = -1};

/* IRQ <-> IPI mapping */
static DEFINE_PER_CPU(int [XEN_NR_IPIS], ipi_to_irq) = {[0 ... XEN_NR_IPIS-1] = -1};

/* Interrupt types. */
enum xen_irq_type {
        IRQT_UNBOUND = 0,
        IRQT_PIRQ,
        IRQT_VIRQ,
        IRQT_IPI,
        IRQT_EVTCHN
};

/*
 * Packed IRQ information:
 * type - enum xen_irq_type
 * event channel - irq->event channel mapping
 * cpu - cpu this event channel is bound to
 * index - type-specific information:
 *    PIRQ - vector, with MSB being "needs EIO"
 *    VIRQ - virq number
 *    IPI - IPI vector
 *    EVTCHN -
 */
struct irq_info
{
        enum xen_irq_type type; /* type */
        unsigned short evtchn;  /* event channel */
        unsigned short cpu;     /* cpu bound */

        union {
                unsigned short virq;
                enum ipi_vector ipi;
                struct {
                        unsigned short gsi;
                        unsigned char vector;
                        unsigned char flags;
                } pirq;
        } u;
};
#define PIRQ_NEEDS_EOI  (1 << 0)

static struct irq_info irq_info[NR_IRQS];

static int evtchn_to_irq[NR_EVENT_CHANNELS] = {
        [0 ... NR_EVENT_CHANNELS-1] = -1
};
struct cpu_evtchn_s {
        unsigned long bits[NR_EVENT_CHANNELS/BITS_PER_LONG];
};
static struct cpu_evtchn_s *cpu_evtchn_mask_p;
static inline unsigned long *cpu_evtchn_mask(int cpu)
{
        return cpu_evtchn_mask_p[cpu].bits;
}

/* Xen will never allocate port zero for any purpose. */
#define VALID_EVTCHN(chn)       ((chn) != 0)

static struct irq_chip xen_dynamic_chip;
static struct irq_chip xen_percpu_chip;
static struct irq_chip xen_pirq_chip;

/* Constructor for packed IRQ information. */
static struct irq_info mk_unbound_info(void)
{
        return (struct irq_info) { .type = IRQT_UNBOUND };
}

static struct irq_info mk_evtchn_info(unsigned short evtchn)
{
        return (struct irq_info) { .type = IRQT_EVTCHN, .evtchn = evtchn,
                        .cpu = 0 };
}

static struct irq_info mk_ipi_info(unsigned short evtchn, enum ipi_vector ipi)
{
        return (struct irq_info) { .type = IRQT_IPI, .evtchn = evtchn,
                        .cpu = 0, .u.ipi = ipi };
}

static struct irq_info mk_virq_info(unsigned short evtchn, unsigned short virq)
{
        return (struct irq_info) { .type = IRQT_VIRQ, .evtchn = evtchn,
                        .cpu = 0, .u.virq = virq };
}

static struct irq_info mk_pirq_info(unsigned short evtchn,
                                    unsigned short gsi, unsigned short vector)
{
        return (struct irq_info) { .type = IRQT_PIRQ, .evtchn = evtchn,
                        .cpu = 0, .u.pirq = { .gsi = gsi, .vector = vector } };
}

/*
 * Accessors for packed IRQ information.
 */
static struct irq_info *info_for_irq(unsigned irq)
{
        return &irq_info[irq];
}

static unsigned int evtchn_from_irq(unsigned irq)
{
        return info_for_irq(irq)->evtchn;
}

unsigned irq_from_evtchn(unsigned int evtchn)
{
        return evtchn_to_irq[evtchn];
}
EXPORT_SYMBOL_GPL(irq_from_evtchn);

static enum ipi_vector ipi_from_irq(unsigned irq)
{
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info == NULL);
        BUG_ON(info->type != IRQT_IPI);

        return info->u.ipi;
}

static unsigned virq_from_irq(unsigned irq)
{
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info == NULL);
        BUG_ON(info->type != IRQT_VIRQ);

        return info->u.virq;
}

static unsigned gsi_from_irq(unsigned irq)
{
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info == NULL);
        BUG_ON(info->type != IRQT_PIRQ);

        return info->u.pirq.gsi;
}

static unsigned vector_from_irq(unsigned irq)
{
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info == NULL);
        BUG_ON(info->type != IRQT_PIRQ);

        return info->u.pirq.vector;
}

static enum xen_irq_type type_from_irq(unsigned irq)
{
        return info_for_irq(irq)->type;
}

static unsigned cpu_from_irq(unsigned irq)
{
        return info_for_irq(irq)->cpu;
}

static unsigned int cpu_from_evtchn(unsigned int evtchn)
{
        int irq = evtchn_to_irq[evtchn];
        unsigned ret = 0;

        if (irq != -1)
                ret = cpu_from_irq(irq);

        return ret;
}

static bool pirq_needs_eoi(unsigned irq)
{
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info->type != IRQT_PIRQ);

        return info->u.pirq.flags & PIRQ_NEEDS_EOI;
}

static inline unsigned long active_evtchns(unsigned int cpu,
                                           struct shared_info *sh,
                                           unsigned int idx)
{
        return (sh->evtchn_pending[idx] &
                cpu_evtchn_mask(cpu)[idx] &
                ~sh->evtchn_mask[idx]);
}

static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
{
        int irq = evtchn_to_irq[chn];

        BUG_ON(irq == -1);
#ifdef CONFIG_SMP
        cpumask_copy(irq_to_desc(irq)->affinity, cpumask_of(cpu));
#endif

        __clear_bit(chn, cpu_evtchn_mask(cpu_from_irq(irq)));
        __set_bit(chn, cpu_evtchn_mask(cpu));

        irq_info[irq].cpu = cpu;
}

static void init_evtchn_cpu_bindings(void)
{
#ifdef CONFIG_SMP
        struct irq_desc *desc;
        int i;

        /* By default all event channels notify CPU#0. */
        for_each_irq_desc(i, desc) {
                cpumask_copy(desc->affinity, cpumask_of(0));
        }
#endif

        memset(cpu_evtchn_mask(0), ~0, sizeof(cpu_evtchn_mask(0)));
}

static inline void clear_evtchn(int port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_clear_bit(port, &s->evtchn_pending[0]);
}

static inline void set_evtchn(int port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_set_bit(port, &s->evtchn_pending[0]);
}

static inline int test_evtchn(int port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        return sync_test_bit(port, &s->evtchn_pending[0]);
}


/**
 * notify_remote_via_irq - send event to remote end of event channel via irq
 * @irq: irq of event channel to send event to
 *
 * Unlike notify_remote_via_evtchn(), this is safe to use across
 * save/restore. Notifications on a broken connection are silently
 * dropped.
 */
void notify_remote_via_irq(int irq)
{
        int evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn))
                notify_remote_via_evtchn(evtchn);
}
EXPORT_SYMBOL_GPL(notify_remote_via_irq);

static void mask_evtchn(int port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        sync_set_bit(port, &s->evtchn_mask[0]);
}

static void unmask_evtchn(int port)
{
        struct shared_info *s = HYPERVISOR_shared_info;
        unsigned int cpu = get_cpu();

        BUG_ON(!irqs_disabled());

        /* Slow path (hypercall) if this is a non-local port. */
        if (unlikely(cpu != cpu_from_evtchn(port))) {
                struct evtchn_unmask unmask = { .port = port };
                (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
        } else {
                struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);

                sync_clear_bit(port, &s->evtchn_mask[0]);

                /*
                 * The following is basically the equivalent of
                 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
                 * the interrupt edge' if the channel is masked.
                 */
                if (sync_test_bit(port, &s->evtchn_pending[0]) &&
                    !sync_test_and_set_bit(port / BITS_PER_LONG,
                                           &vcpu_info->evtchn_pending_sel))
                        vcpu_info->evtchn_upcall_pending = 1;
        }

        put_cpu();
}

static int find_unbound_irq(void)
{
        struct irq_data *data;
        int irq, res;

        for (irq = 0; irq < nr_irqs; irq++) {
                data = irq_get_irq_data(irq);
                /* only 0->15 have init'd desc; handle irq > 16 */
                if (!data)
                        break;
                if (data->chip == &no_irq_chip)
                        break;
                if (data->chip != &xen_dynamic_chip)
                        continue;
                if (irq_info[irq].type == IRQT_UNBOUND)
                        return irq;
        }

        if (irq == nr_irqs)
                panic("No available IRQ to bind to: increase nr_irqs!\n");

        res = irq_alloc_desc_at(irq, 0);

        if (WARN_ON(res != irq))
                return -1;

        return irq;
}

static bool identity_mapped_irq(unsigned irq)
{
        /* only identity map legacy irqs */
        return irq < LEGACY_IRQS;
}

static void pirq_unmask_notify(int irq)
{
        struct physdev_eoi eoi = { .irq = irq };

        if (unlikely(pirq_needs_eoi(irq))) {
                int rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
                WARN_ON(rc);
        }
}

static void pirq_query_unmask(int irq)
{
        struct physdev_irq_status_query irq_status;
        struct irq_info *info = info_for_irq(irq);

        BUG_ON(info->type != IRQT_PIRQ);

        irq_status.irq = irq;
        if (HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status))
                irq_status.flags = 0;

        info->u.pirq.flags &= ~PIRQ_NEEDS_EOI;
        if (irq_status.flags & XENIRQSTAT_needs_eoi)
                info->u.pirq.flags |= PIRQ_NEEDS_EOI;
}

static bool probing_irq(int irq)
{
        struct irq_desc *desc = irq_to_desc(irq);

        return desc && desc->action == NULL;
}

static unsigned int startup_pirq(unsigned int irq)
{
        struct evtchn_bind_pirq bind_pirq;
        struct irq_info *info = info_for_irq(irq);
        int evtchn = evtchn_from_irq(irq);

        BUG_ON(info->type != IRQT_PIRQ);

        if (VALID_EVTCHN(evtchn))
                goto out;

        bind_pirq.pirq = irq;
        /* NB. We are happy to share unless we are probing. */
        bind_pirq.flags = probing_irq(irq) ? 0 : BIND_PIRQ__WILL_SHARE;
        if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_pirq, &bind_pirq) != 0) {
                if (!probing_irq(irq))
                        printk(KERN_INFO "Failed to obtain physical IRQ %d\n",
                               irq);
                return 0;
        }
        evtchn = bind_pirq.port;

        pirq_query_unmask(irq);

        evtchn_to_irq[evtchn] = irq;
        bind_evtchn_to_cpu(evtchn, 0);
        info->evtchn = evtchn;

out:
        unmask_evtchn(evtchn);
        pirq_unmask_notify(irq);

        return 0;
}

static void shutdown_pirq(unsigned int irq)
{
        struct evtchn_close close;
        struct irq_info *info = info_for_irq(irq);
        int evtchn = evtchn_from_irq(irq);

        BUG_ON(info->type != IRQT_PIRQ);

        if (!VALID_EVTCHN(evtchn))
                return;

        mask_evtchn(evtchn);

        close.port = evtchn;
        if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
                BUG();

        bind_evtchn_to_cpu(evtchn, 0);
        evtchn_to_irq[evtchn] = -1;
        info->evtchn = 0;
}

static void enable_pirq(unsigned int irq)
{
        startup_pirq(irq);
}

static void disable_pirq(unsigned int irq)
{
}

static void ack_pirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);

        move_native_irq(irq);

        if (VALID_EVTCHN(evtchn)) {
                mask_evtchn(evtchn);
                clear_evtchn(evtchn);
        }
}

static void end_pirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);
        struct irq_desc *desc = irq_to_desc(irq);

        if (WARN_ON(!desc))
                return;

        if ((desc->status & (IRQ_DISABLED|IRQ_PENDING)) ==
            (IRQ_DISABLED|IRQ_PENDING)) {
                shutdown_pirq(irq);
        } else if (VALID_EVTCHN(evtchn)) {
                unmask_evtchn(evtchn);
                pirq_unmask_notify(irq);
        }
}

static int find_irq_by_gsi(unsigned gsi)
{
        int irq;

        for (irq = 0; irq < NR_IRQS; irq++) {
                struct irq_info *info = info_for_irq(irq);

                if (info == NULL || info->type != IRQT_PIRQ)
                        continue;

                if (gsi_from_irq(irq) == gsi)
                        return irq;
        }

        return -1;
}

/*
 * Allocate a physical irq, along with a vector.  We don't assign an
 * event channel until the irq actually started up.  Return an
 * existing irq if we've already got one for the gsi.
 */
int xen_allocate_pirq(unsigned gsi)
{
        int irq;
        struct physdev_irq irq_op;

        spin_lock(&irq_mapping_update_lock);

        irq = find_irq_by_gsi(gsi);
        if (irq != -1) {
                printk(KERN_INFO "xen_allocate_pirq: returning irq %d for gsi %u\n",
                       irq, gsi);
                goto out;       /* XXX need refcount? */
        }

        if (identity_mapped_irq(gsi)) {
                irq = gsi;
                dynamic_irq_init(irq);
        } else
                irq = find_unbound_irq();

        set_irq_chip_and_handler_name(irq, &xen_pirq_chip,
                                      handle_level_irq, "pirq");

        irq_op.irq = irq;
        if (HYPERVISOR_physdev_op(PHYSDEVOP_alloc_irq_vector, &irq_op)) {
                dynamic_irq_cleanup(irq);
                irq = -ENOSPC;
                goto out;
        }

        irq_info[irq] = mk_pirq_info(0, gsi, irq_op.vector);

out:
        spin_unlock(&irq_mapping_update_lock);

        return irq;
}

int xen_vector_from_irq(unsigned irq)
{
        return vector_from_irq(irq);
}

int xen_gsi_from_irq(unsigned irq)
{
        return gsi_from_irq(irq);
}

int bind_evtchn_to_irq(unsigned int evtchn)
{
        int irq;

        spin_lock(&irq_mapping_update_lock);

        irq = evtchn_to_irq[evtchn];

        if (irq == -1) {
                irq = find_unbound_irq();

                set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
                                              handle_edge_irq, "event");

                evtchn_to_irq[evtchn] = irq;
                irq_info[irq] = mk_evtchn_info(evtchn);
        }

        spin_unlock(&irq_mapping_update_lock);

        return irq;
}
EXPORT_SYMBOL_GPL(bind_evtchn_to_irq);

static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
{
        struct evtchn_bind_ipi bind_ipi;
        int evtchn, irq;

        spin_lock(&irq_mapping_update_lock);

        irq = per_cpu(ipi_to_irq, cpu)[ipi];

        if (irq == -1) {
                irq = find_unbound_irq();
                if (irq < 0)
                        goto out;

                set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
                                              handle_percpu_irq, "ipi");

                bind_ipi.vcpu = cpu;
                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
                                                &bind_ipi) != 0)
                        BUG();
                evtchn = bind_ipi.port;

                evtchn_to_irq[evtchn] = irq;
                irq_info[irq] = mk_ipi_info(evtchn, ipi);
                per_cpu(ipi_to_irq, cpu)[ipi] = irq;

                bind_evtchn_to_cpu(evtchn, cpu);
        }

 out:
        spin_unlock(&irq_mapping_update_lock);
        return irq;
}


static int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
{
        struct evtchn_bind_virq bind_virq;
        int evtchn, irq;

        spin_lock(&irq_mapping_update_lock);

        irq = per_cpu(virq_to_irq, cpu)[virq];

        if (irq == -1) {
                bind_virq.virq = virq;
                bind_virq.vcpu = cpu;
                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
                                                &bind_virq) != 0)
                        BUG();
                evtchn = bind_virq.port;

                irq = find_unbound_irq();

                set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
                                              handle_percpu_irq, "virq");

                evtchn_to_irq[evtchn] = irq;
                irq_info[irq] = mk_virq_info(evtchn, virq);

                per_cpu(virq_to_irq, cpu)[virq] = irq;

                bind_evtchn_to_cpu(evtchn, cpu);
        }

        spin_unlock(&irq_mapping_update_lock);

        return irq;
}

static void unbind_from_irq(unsigned int irq)
{
        struct evtchn_close close;
        int evtchn = evtchn_from_irq(irq);

        spin_lock(&irq_mapping_update_lock);

        if (VALID_EVTCHN(evtchn)) {
                close.port = evtchn;
                if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
                        BUG();

                switch (type_from_irq(irq)) {
                case IRQT_VIRQ:
                        per_cpu(virq_to_irq, cpu_from_evtchn(evtchn))
                                [virq_from_irq(irq)] = -1;
                        break;
                case IRQT_IPI:
                        per_cpu(ipi_to_irq, cpu_from_evtchn(evtchn))
                                [ipi_from_irq(irq)] = -1;
                        break;
                default:
                        break;
                }

                /* Closed ports are implicitly re-bound to VCPU0. */
                bind_evtchn_to_cpu(evtchn, 0);

                evtchn_to_irq[evtchn] = -1;
        }

        if (irq_info[irq].type != IRQT_UNBOUND) {
                irq_info[irq] = mk_unbound_info();

                irq_free_desc(irq);
        }

        spin_unlock(&irq_mapping_update_lock);
}

int bind_evtchn_to_irqhandler(unsigned int evtchn,
                              irq_handler_t handler,
                              unsigned long irqflags,
                              const char *devname, void *dev_id)
{
        unsigned int irq;
        int retval;

        irq = bind_evtchn_to_irq(evtchn);
        retval = request_irq(irq, handler, irqflags, devname, dev_id);
        if (retval != 0) {
                unbind_from_irq(irq);
                return retval;
        }

        return irq;
}
EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler);

int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
                            irq_handler_t handler,
                            unsigned long irqflags, const char *devname, void *dev_id)
{
        unsigned int irq;
        int retval;

        irq = bind_virq_to_irq(virq, cpu);
        retval = request_irq(irq, handler, irqflags, devname, dev_id);
        if (retval != 0) {
                unbind_from_irq(irq);
                return retval;
        }

        return irq;
}
EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);

int bind_ipi_to_irqhandler(enum ipi_vector ipi,
                           unsigned int cpu,
                           irq_handler_t handler,
                           unsigned long irqflags,
                           const char *devname,
                           void *dev_id)
{
        int irq, retval;

        irq = bind_ipi_to_irq(ipi, cpu);
        if (irq < 0)
                return irq;

        irqflags |= IRQF_NO_SUSPEND;
        retval = request_irq(irq, handler, irqflags, devname, dev_id);
        if (retval != 0) {
                unbind_from_irq(irq);
                return retval;
        }

        return irq;
}

void unbind_from_irqhandler(unsigned int irq, void *dev_id)
{
        free_irq(irq, dev_id);
        unbind_from_irq(irq);
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);

void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
        int irq = per_cpu(ipi_to_irq, cpu)[vector];
        BUG_ON(irq < 0);
        notify_remote_via_irq(irq);
}

irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
{
        struct shared_info *sh = HYPERVISOR_shared_info;
        int cpu = smp_processor_id();
        int i;
        unsigned long flags;
        static DEFINE_SPINLOCK(debug_lock);

        spin_lock_irqsave(&debug_lock, flags);

        printk("vcpu %d\n  ", cpu);

        for_each_online_cpu(i) {
                struct vcpu_info *v = per_cpu(xen_vcpu, i);
                printk("%d: masked=%d pending=%d event_sel %08lx\n  ", i,
                        (get_irq_regs() && i == cpu) ? xen_irqs_disabled(get_irq_regs()) : v->evtchn_upcall_mask,
                        v->evtchn_upcall_pending,
                        v->evtchn_pending_sel);
        }
        printk("pending:\n   ");
        for(i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
                printk("%08lx%s", sh->evtchn_pending[i],
                        i % 8 == 0 ? "\n   " : " ");
        printk("\nmasks:\n   ");
        for(i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
                printk("%08lx%s", sh->evtchn_mask[i],
                        i % 8 == 0 ? "\n   " : " ");

        printk("\nunmasked:\n   ");
        for(i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
                printk("%08lx%s", sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
                        i % 8 == 0 ? "\n   " : " ");

        printk("\npending list:\n");
        for(i = 0; i < NR_EVENT_CHANNELS; i++) {
                if (sync_test_bit(i, sh->evtchn_pending)) {
                        printk("  %d: event %d -> irq %d\n",
                               cpu_from_evtchn(i), i,
                               evtchn_to_irq[i]);
                }
        }

        spin_unlock_irqrestore(&debug_lock, flags);

        return IRQ_HANDLED;
}

static DEFINE_PER_CPU(unsigned, xed_nesting_count);

/*
 * Search the CPUs pending events bitmasks.  For each one found, map
 * the event number to an irq, and feed it into do_IRQ() for
 * handling.
 *
 * Xen uses a two-level bitmap to speed searching.  The first level is
 * a bitset of words which contain pending event bits.  The second
 * level is a bitset of pending events themselves.
 */
static void __xen_evtchn_do_upcall(void)
{
        int cpu = get_cpu();
        struct shared_info *s = HYPERVISOR_shared_info;
        struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
        unsigned count;

        do {
                unsigned long pending_words;

                vcpu_info->evtchn_upcall_pending = 0;

                if (__get_cpu_var(xed_nesting_count)++)
                        goto out;

#ifndef CONFIG_X86 /* No need for a barrier -- XCHG is a barrier on x86. */
                /* Clear master flag /before/ clearing selector flag. */
                wmb();
#endif
                pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
                while (pending_words != 0) {
                        unsigned long pending_bits;
                        int word_idx = __ffs(pending_words);
                        pending_words &= ~(1UL << word_idx);

                        while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
                                int bit_idx = __ffs(pending_bits);
                                int port = (word_idx * BITS_PER_LONG) + bit_idx;
                                int irq = evtchn_to_irq[port];
                                struct irq_desc *desc;

                                if (irq != -1) {
                                        desc = irq_to_desc(irq);
                                        if (desc)
                                                generic_handle_irq_desc(irq, desc);
                                }
                        }
                }

                BUG_ON(!irqs_disabled());

                count = __get_cpu_var(xed_nesting_count);
                __get_cpu_var(xed_nesting_count) = 0;
        } while (count != 1 || vcpu_info->evtchn_upcall_pending);

out:

        put_cpu();
}

void xen_evtchn_do_upcall(struct pt_regs *regs)
{
        struct pt_regs *old_regs = set_irq_regs(regs);

        exit_idle();
        irq_enter();

        __xen_evtchn_do_upcall();

        irq_exit();
        set_irq_regs(old_regs);
}

void xen_hvm_evtchn_do_upcall(void)
{
        __xen_evtchn_do_upcall();
}
EXPORT_SYMBOL_GPL(xen_hvm_evtchn_do_upcall);

/* Rebind a new event channel to an existing irq. */
void rebind_evtchn_irq(int evtchn, int irq)
{
        struct irq_info *info = info_for_irq(irq);

        /* Make sure the irq is masked, since the new event channel
           will also be masked. */
        disable_irq(irq);

        spin_lock(&irq_mapping_update_lock);

        /* After resume the irq<->evtchn mappings are all cleared out */
        BUG_ON(evtchn_to_irq[evtchn] != -1);
        /* Expect irq to have been bound before,
           so there should be a proper type */
        BUG_ON(info->type == IRQT_UNBOUND);

        evtchn_to_irq[evtchn] = irq;
        irq_info[irq] = mk_evtchn_info(evtchn);

        spin_unlock(&irq_mapping_update_lock);

        /* new event channels are always bound to cpu 0 */
        irq_set_affinity(irq, cpumask_of(0));

        /* Unmask the event channel. */
        enable_irq(irq);
}

/* Rebind an evtchn so that it gets delivered to a specific cpu */
static int rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
{
        struct evtchn_bind_vcpu bind_vcpu;
        int evtchn = evtchn_from_irq(irq);

        /* events delivered via platform PCI interrupts are always
         * routed to vcpu 0 */
        if (!VALID_EVTCHN(evtchn) ||
                (xen_hvm_domain() && !xen_have_vector_callback))
                return -1;

        /* Send future instances of this interrupt to other vcpu. */
        bind_vcpu.port = evtchn;
        bind_vcpu.vcpu = tcpu;

        /*
         * If this fails, it usually just indicates that we're dealing with a
         * virq or IPI channel, which don't actually need to be rebound. Ignore
         * it, but don't do the xenlinux-level rebind in that case.
         */
        if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
                bind_evtchn_to_cpu(evtchn, tcpu);

        return 0;
}

static int set_affinity_irq(unsigned irq, const struct cpumask *dest)
{
        unsigned tcpu = cpumask_first(dest);

        return rebind_irq_to_cpu(irq, tcpu);
}

int resend_irq_on_evtchn(unsigned int irq)
{
        int masked, evtchn = evtchn_from_irq(irq);
        struct shared_info *s = HYPERVISOR_shared_info;

        if (!VALID_EVTCHN(evtchn))
                return 1;

        masked = sync_test_and_set_bit(evtchn, s->evtchn_mask);
        sync_set_bit(evtchn, s->evtchn_pending);
        if (!masked)
                unmask_evtchn(evtchn);

        return 1;
}

static void enable_dynirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn))
                unmask_evtchn(evtchn);
}

static void disable_dynirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn))
                mask_evtchn(evtchn);
}

static void ack_dynirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);

        move_native_irq(irq);

        if (VALID_EVTCHN(evtchn))
                clear_evtchn(evtchn);
}

static int retrigger_dynirq(unsigned int irq)
{
        int evtchn = evtchn_from_irq(irq);
        struct shared_info *sh = HYPERVISOR_shared_info;
        int ret = 0;

        if (VALID_EVTCHN(evtchn)) {
                int masked;

                masked = sync_test_and_set_bit(evtchn, sh->evtchn_mask);
                sync_set_bit(evtchn, sh->evtchn_pending);
                if (!masked)
                        unmask_evtchn(evtchn);
                ret = 1;
        }

        return ret;
}

static void restore_cpu_virqs(unsigned int cpu)
{
        struct evtchn_bind_virq bind_virq;
        int virq, irq, evtchn;

        for (virq = 0; virq < NR_VIRQS; virq++) {
                if ((irq = per_cpu(virq_to_irq, cpu)[virq]) == -1)
                        continue;

                BUG_ON(virq_from_irq(irq) != virq);

                /* Get a new binding from Xen. */
                bind_virq.virq = virq;
                bind_virq.vcpu = cpu;
                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
                                                &bind_virq) != 0)
                        BUG();
                evtchn = bind_virq.port;

                /* Record the new mapping. */
                evtchn_to_irq[evtchn] = irq;
                irq_info[irq] = mk_virq_info(evtchn, virq);
                bind_evtchn_to_cpu(evtchn, cpu);

                /* Ready for use. */
                unmask_evtchn(evtchn);
        }
}

static void restore_cpu_ipis(unsigned int cpu)
{
        struct evtchn_bind_ipi bind_ipi;
        int ipi, irq, evtchn;

        for (ipi = 0; ipi < XEN_NR_IPIS; ipi++) {
                if ((irq = per_cpu(ipi_to_irq, cpu)[ipi]) == -1)
                        continue;

                BUG_ON(ipi_from_irq(irq) != ipi);

                /* Get a new binding from Xen. */
                bind_ipi.vcpu = cpu;
                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
                                                &bind_ipi) != 0)
                        BUG();
                evtchn = bind_ipi.port;

                /* Record the new mapping. */
                evtchn_to_irq[evtchn] = irq;
                irq_info[irq] = mk_ipi_info(evtchn, ipi);
                bind_evtchn_to_cpu(evtchn, cpu);

                /* Ready for use. */
                unmask_evtchn(evtchn);

        }
}

/* Clear an irq's pending state, in preparation for polling on it */
void xen_clear_irq_pending(int irq)
{
        int evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn))
                clear_evtchn(evtchn);
}

void xen_set_irq_pending(int irq)
{
        int evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn))
                set_evtchn(evtchn);
}

bool xen_test_irq_pending(int irq)
{
        int evtchn = evtchn_from_irq(irq);
        bool ret = false;

        if (VALID_EVTCHN(evtchn))
                ret = test_evtchn(evtchn);

        return ret;
}

/* Poll waiting for an irq to become pending.  In the usual case, the
   irq will be disabled so it won't deliver an interrupt. */
void xen_poll_irq(int irq)
{
        evtchn_port_t evtchn = evtchn_from_irq(irq);

        if (VALID_EVTCHN(evtchn)) {
                struct sched_poll poll;

                poll.nr_ports = 1;
                poll.timeout = 0;
                set_xen_guest_handle(poll.ports, &evtchn);

                if (HYPERVISOR_sched_op(SCHEDOP_poll, &poll) != 0)
                        BUG();
        }
}

void xen_irq_resume(void)
{
        unsigned int cpu, irq, evtchn;

        init_evtchn_cpu_bindings();

        /* New event-channel space is not 'live' yet. */
        for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
                mask_evtchn(evtchn);

        /* No IRQ <-> event-channel mappings. */
        for (irq = 0; irq < nr_irqs; irq++)
                irq_info[irq].evtchn = 0; /* zap event-channel binding */

        for (evtchn = 0; evtchn < NR_EVENT_CHANNELS; evtchn++)
                evtchn_to_irq[evtchn] = -1;

        for_each_possible_cpu(cpu) {
                restore_cpu_virqs(cpu);
                restore_cpu_ipis(cpu);
        }
}

static struct irq_chip xen_dynamic_chip __read_mostly = {
        .name           = "xen-dyn",

        .disable        = disable_dynirq,
        .mask           = disable_dynirq,
        .unmask         = enable_dynirq,

        .ack            = ack_dynirq,
        .set_affinity   = set_affinity_irq,
        .retrigger      = retrigger_dynirq,
};

static struct irq_chip xen_pirq_chip __read_mostly = {
        .name           = "xen-pirq",

        .startup        = startup_pirq,
        .shutdown       = shutdown_pirq,

        .enable         = enable_pirq,
        .unmask         = enable_pirq,

        .disable        = disable_pirq,
        .mask           = disable_pirq,

        .ack            = ack_pirq,
        .end            = end_pirq,

        .set_affinity   = set_affinity_irq,

        .retrigger      = retrigger_dynirq,
};

static struct irq_chip xen_percpu_chip __read_mostly = {
        .name           = "xen-percpu",

        .disable        = disable_dynirq,
        .mask           = disable_dynirq,
        .unmask         = enable_dynirq,

        .ack            = ack_dynirq,
};

int xen_set_callback_via(uint64_t via)
{
        struct xen_hvm_param a;
        a.domid = DOMID_SELF;
        a.index = HVM_PARAM_CALLBACK_IRQ;
        a.value = via;
        return HYPERVISOR_hvm_op(HVMOP_set_param, &a);
}
EXPORT_SYMBOL_GPL(xen_set_callback_via);

#ifdef CONFIG_XEN_PVHVM
/* Vector callbacks are better than PCI interrupts to receive event
 * channel notifications because we can receive vector callbacks on any
 * vcpu and we don't need PCI support or APIC interactions. */
void xen_callback_vector(void)
{
        int rc;
        uint64_t callback_via;
        if (xen_have_vector_callback) {
                callback_via = HVM_CALLBACK_VECTOR(XEN_HVM_EVTCHN_CALLBACK);
                rc = xen_set_callback_via(callback_via);
                if (rc) {
                        printk(KERN_ERR "Request for Xen HVM callback vector"
                                        " failed.\n");
                        xen_have_vector_callback = 0;
                        return;
                }
                printk(KERN_INFO "Xen HVM callback vector for event delivery is "
                                "enabled\n");
                /* in the restore case the vector has already been allocated */
                if (!test_bit(XEN_HVM_EVTCHN_CALLBACK, used_vectors))
                        alloc_intr_gate(XEN_HVM_EVTCHN_CALLBACK, xen_hvm_callback_vector);
        }
}
#else
void xen_callback_vector(void) {}
#endif

void __init xen_init_IRQ(void)
{
        int i;

        cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
                                    GFP_KERNEL);
        BUG_ON(cpu_evtchn_mask_p == NULL);

        init_evtchn_cpu_bindings();

        /* No event channels are 'live' right now. */
        for (i = 0; i < NR_EVENT_CHANNELS; i++)
                mask_evtchn(i);

        if (xen_hvm_domain()) {
                xen_callback_vector();
                native_init_IRQ();
        } else {
                irq_ctx_init(smp_processor_id());
        }
}