events_base.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 received, 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
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#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 <linux/irqnr.h>
#include <linux/pci.h>

#ifdef CONFIG_X86
#include <asm/desc.h>
#include <asm/ptrace.h>
#include <asm/irq.h>
#include <asm/idle.h>
#include <asm/io_apic.h>
#include <asm/xen/page.h>
#include <asm/xen/pci.h>
#endif
#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>
#include <xen/interface/physdev.h>
#include <xen/interface/sched.h>
#include <xen/interface/vcpu.h>
#include <asm/hw_irq.h>

#include "events_internal.h"

const struct evtchn_ops *evtchn_ops;

/*
 * 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_MUTEX(irq_mapping_update_lock);

static LIST_HEAD(xen_irq_list_head);

/* 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};

int **evtchn_to_irq;
#ifdef CONFIG_X86
static unsigned long *pirq_eoi_map;
#endif
static bool (*pirq_needs_eoi)(unsigned irq);

#define EVTCHN_ROW(e)  (e / (PAGE_SIZE/sizeof(**evtchn_to_irq)))
#define EVTCHN_COL(e)  (e % (PAGE_SIZE/sizeof(**evtchn_to_irq)))
#define EVTCHN_PER_ROW (PAGE_SIZE / sizeof(**evtchn_to_irq))

/* 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;
static void enable_dynirq(struct irq_data *data);
static void disable_dynirq(struct irq_data *data);

static void clear_evtchn_to_irq_row(unsigned row)
{
	unsigned col;

	for (col = 0; col < EVTCHN_PER_ROW; col++)
		evtchn_to_irq[row][col] = -1;
}

static void clear_evtchn_to_irq_all(void)
{
	unsigned row;

	for (row = 0; row < EVTCHN_ROW(xen_evtchn_max_channels()); row++) {
		if (evtchn_to_irq[row] == NULL)
			continue;
		clear_evtchn_to_irq_row(row);
	}
}

static int set_evtchn_to_irq(unsigned evtchn, unsigned irq)
{
	unsigned row;
	unsigned col;

	if (evtchn >= xen_evtchn_max_channels())
		return -EINVAL;

	row = EVTCHN_ROW(evtchn);
	col = EVTCHN_COL(evtchn);

	if (evtchn_to_irq[row] == NULL) {
		/* Unallocated irq entries return -1 anyway */
		if (irq == -1)
			return 0;

		evtchn_to_irq[row] = (int *)get_zeroed_page(GFP_KERNEL);
		if (evtchn_to_irq[row] == NULL)
			return -ENOMEM;

		clear_evtchn_to_irq_row(row);
	}

	evtchn_to_irq[EVTCHN_ROW(evtchn)][EVTCHN_COL(evtchn)] = irq;
	return 0;
}

int get_evtchn_to_irq(unsigned evtchn)
{
	if (evtchn >= xen_evtchn_max_channels())
		return -1;
	if (evtchn_to_irq[EVTCHN_ROW(evtchn)] == NULL)
		return -1;
	return evtchn_to_irq[EVTCHN_ROW(evtchn)][EVTCHN_COL(evtchn)];
}

/* Get info for IRQ */
struct irq_info *info_for_irq(unsigned irq)
{
	return irq_get_handler_data(irq);
}

/* Constructors for packed IRQ information. */
static int xen_irq_info_common_setup(struct irq_info *info,
				     unsigned irq,
				     enum xen_irq_type type,
				     unsigned evtchn,
				     unsigned short cpu)
{
	int ret;

	BUG_ON(info->type != IRQT_UNBOUND && info->type != type);

	info->type = type;
	info->irq = irq;
	info->evtchn = evtchn;
	info->cpu = cpu;

	ret = set_evtchn_to_irq(evtchn, irq);
	if (ret < 0)
		return ret;

	irq_clear_status_flags(irq, IRQ_NOREQUEST|IRQ_NOAUTOEN);

	return xen_evtchn_port_setup(info);
}

static int xen_irq_info_evtchn_setup(unsigned irq,
				     unsigned evtchn)
{
	struct irq_info *info = info_for_irq(irq);

	return xen_irq_info_common_setup(info, irq, IRQT_EVTCHN, evtchn, 0);
}

static int xen_irq_info_ipi_setup(unsigned cpu,
				  unsigned irq,
				  unsigned evtchn,
				  enum ipi_vector ipi)
{
	struct irq_info *info = info_for_irq(irq);

	info->u.ipi = ipi;

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

	return xen_irq_info_common_setup(info, irq, IRQT_IPI, evtchn, 0);
}

static int xen_irq_info_virq_setup(unsigned cpu,
				   unsigned irq,
				   unsigned evtchn,
				   unsigned virq)
{
	struct irq_info *info = info_for_irq(irq);

	info->u.virq = virq;

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

	return xen_irq_info_common_setup(info, irq, IRQT_VIRQ, evtchn, 0);
}

static int xen_irq_info_pirq_setup(unsigned irq,
				   unsigned evtchn,
				   unsigned pirq,
				   unsigned gsi,
				   uint16_t domid,
				   unsigned char flags)
{
	struct irq_info *info = info_for_irq(irq);

	info->u.pirq.pirq = pirq;
	info->u.pirq.gsi = gsi;
	info->u.pirq.domid = domid;
	info->u.pirq.flags = flags;

	return xen_irq_info_common_setup(info, irq, IRQT_PIRQ, evtchn, 0);
}

static void xen_irq_info_cleanup(struct irq_info *info)
{
	set_evtchn_to_irq(info->evtchn, -1);
	info->evtchn = 0;
}

/*
 * Accessors for packed IRQ information.
 */
unsigned int evtchn_from_irq(unsigned irq)
{
	if (unlikely(WARN(irq < 0 || irq >= nr_irqs, "Invalid irq %d!\n", irq)))
		return 0;

	return info_for_irq(irq)->evtchn;
}

unsigned irq_from_evtchn(unsigned int evtchn)
{
	return get_evtchn_to_irq(evtchn);
}
EXPORT_SYMBOL_GPL(irq_from_evtchn);

int irq_from_virq(unsigned int cpu, unsigned int virq)
{
	return per_cpu(virq_to_irq, cpu)[virq];
}

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 pirq_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.pirq;
}

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

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

unsigned int cpu_from_evtchn(unsigned int evtchn)
{
	int irq = get_evtchn_to_irq(evtchn);
	unsigned ret = 0;

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

	return ret;
}

#ifdef CONFIG_X86
static bool pirq_check_eoi_map(unsigned irq)
{
	return test_bit(pirq_from_irq(irq), pirq_eoi_map);
}
#endif

static bool pirq_needs_eoi_flag(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 void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
{
	int irq = get_evtchn_to_irq(chn);
	struct irq_info *info = info_for_irq(irq);

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

	xen_evtchn_port_bind_to_cpu(info, cpu);

	info->cpu = cpu;
}

static void xen_evtchn_mask_all(void)
{
	unsigned int evtchn;

	for (evtchn = 0; evtchn < xen_evtchn_nr_channels(); evtchn++)
		mask_evtchn(evtchn);
}

/**
 * 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 xen_irq_init(unsigned irq)
{
	struct irq_info *info;
#ifdef CONFIG_SMP
	struct irq_desc *desc = irq_to_desc(irq);

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

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (info == NULL)
		panic("Unable to allocate metadata for IRQ%d\n", irq);

	info->type = IRQT_UNBOUND;
	info->refcnt = -1;

	irq_set_handler_data(irq, info);

	list_add_tail(&info->list, &xen_irq_list_head);
}

static int __must_check xen_allocate_irq_dynamic(void)
{
	int first = 0;
	int irq;

#ifdef CONFIG_X86_IO_APIC
	/*
	 * For an HVM guest or domain 0 which see "real" (emulated or
	 * actual respectively) GSIs we allocate dynamic IRQs
	 * e.g. those corresponding to event channels or MSIs
	 * etc. from the range above those "real" GSIs to avoid
	 * collisions.
	 */
	if (xen_initial_domain() || xen_hvm_domain())
		first = get_nr_irqs_gsi();
#endif

	irq = irq_alloc_desc_from(first, -1);

	if (irq >= 0)
		xen_irq_init(irq);

	return irq;
}

static int __must_check xen_allocate_irq_gsi(unsigned gsi)
{
	int irq;

	/*
	 * A PV guest has no concept of a GSI (since it has no ACPI
	 * nor access to/knowledge of the physical APICs). Therefore
	 * all IRQs are dynamically allocated from the entire IRQ
	 * space.
	 */
	if (xen_pv_domain() && !xen_initial_domain())
		return xen_allocate_irq_dynamic();

	/* Legacy IRQ descriptors are already allocated by the arch. */
	if (gsi < NR_IRQS_LEGACY)
		irq = gsi;
	else
		irq = irq_alloc_desc_at(gsi, -1);

	xen_irq_init(irq);

	return irq;
}

static void xen_free_irq(unsigned irq)
{
	struct irq_info *info = irq_get_handler_data(irq);

	if (WARN_ON(!info))
		return;

	list_del(&info->list);

	irq_set_handler_data(irq, NULL);

	WARN_ON(info->refcnt > 0);

	kfree(info);

	/* Legacy IRQ descriptors are managed by the arch. */
	if (irq < NR_IRQS_LEGACY)
		return;

	irq_free_desc(irq);
}

static void xen_evtchn_close(unsigned int port)
{
	struct evtchn_close close;

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

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

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 = pirq_from_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 void eoi_pirq(struct irq_data *data)
{
	int evtchn = evtchn_from_irq(data->irq);
	struct physdev_eoi eoi = { .irq = pirq_from_irq(data->irq) };
	int rc = 0;

	irq_move_irq(data);

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

	if (pirq_needs_eoi(data->irq)) {
		rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
		WARN_ON(rc);
	}
}

static void mask_ack_pirq(struct irq_data *data)
{
	disable_dynirq(data);
	eoi_pirq(data);
}

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);
	int rc;

	BUG_ON(info->type != IRQT_PIRQ);

	if (VALID_EVTCHN(evtchn))
		goto out;

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

	pirq_query_unmask(irq);

	rc = set_evtchn_to_irq(evtchn, irq);
	if (rc != 0) {
		pr_err("irq%d: Failed to set port to irq mapping (%d)\n",
		       irq, rc);
		xen_evtchn_close(evtchn);
		return 0;
	}
	bind_evtchn_to_cpu(evtchn, 0);
	info->evtchn = evtchn;

out:
	unmask_evtchn(evtchn);
	eoi_pirq(irq_get_irq_data(irq));

	return 0;
}

static unsigned int startup_pirq(struct irq_data *data)
{
	return __startup_pirq(data->irq);
}

static void shutdown_pirq(struct irq_data *data)
{
	unsigned int irq = data->irq;
	struct irq_info *info = info_for_irq(irq);
	unsigned evtchn = evtchn_from_irq(irq);

	BUG_ON(info->type != IRQT_PIRQ);

	if (!VALID_EVTCHN(evtchn))
		return;

	mask_evtchn(evtchn);
	xen_evtchn_close(evtchn);
	xen_irq_info_cleanup(info);
}

static void enable_pirq(struct irq_data *data)
{
	startup_pirq(data);
}

static void disable_pirq(struct irq_data *data)
{
	disable_dynirq(data);
}

int xen_irq_from_gsi(unsigned gsi)
{
	struct irq_info *info;

	list_for_each_entry(info, &xen_irq_list_head, list) {
		if (info->type != IRQT_PIRQ)
			continue;

		if (info->u.pirq.gsi == gsi)
			return info->irq;
	}

	return -1;
}
EXPORT_SYMBOL_GPL(xen_irq_from_gsi);

static void __unbind_from_irq(unsigned int irq)
{
	int evtchn = evtchn_from_irq(irq);
	struct irq_info *info = irq_get_handler_data(irq);

	if (info->refcnt > 0) {
		info->refcnt--;
		if (info->refcnt != 0)
			return;
	}

	if (VALID_EVTCHN(evtchn)) {
		unsigned int cpu = cpu_from_irq(irq);

		xen_evtchn_close(evtchn);

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

		xen_irq_info_cleanup(info);
	}

	BUG_ON(info_for_irq(irq)->type == IRQT_UNBOUND);

	xen_free_irq(irq);
}

/*
 * Do not make any assumptions regarding the relationship between the
 * IRQ number returned here and the Xen pirq argument.
 *
 * Note: 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.
 *
 * Shareable implies level triggered, not shareable implies edge
 * triggered here.
 */
int xen_bind_pirq_gsi_to_irq(unsigned gsi,
			     unsigned pirq, int shareable, char *name)
{
	int irq = -1;
	struct physdev_irq irq_op;
	int ret;

	mutex_lock(&irq_mapping_update_lock);

	irq = xen_irq_from_gsi(gsi);
	if (irq != -1) {
		pr_info("%s: returning irq %d for gsi %u\n",
			__func__, irq, gsi);
		goto out;
	}

	irq = xen_allocate_irq_gsi(gsi);
	if (irq < 0)
		goto out;

	irq_op.irq = irq;
	irq_op.vector = 0;

	/* Only the privileged domain can do this. For non-priv, the pcifront
	 * driver provides a PCI bus that does the call to do exactly
	 * this in the priv domain. */
	if (xen_initial_domain() &&
	    HYPERVISOR_physdev_op(PHYSDEVOP_alloc_irq_vector, &irq_op)) {
		xen_free_irq(irq);
		irq = -ENOSPC;
		goto out;
	}

	ret = xen_irq_info_pirq_setup(irq, 0, pirq, gsi, DOMID_SELF,
			       shareable ? PIRQ_SHAREABLE : 0);
	if (ret < 0) {
		__unbind_from_irq(irq);
		irq = ret;
		goto out;
	}

	pirq_query_unmask(irq);
	/* We try to use the handler with the appropriate semantic for the
	 * type of interrupt: if the interrupt is an edge triggered
	 * interrupt we use handle_edge_irq.
	 *
	 * On the other hand if the interrupt is level triggered we use
	 * handle_fasteoi_irq like the native code does for this kind of
	 * interrupts.
	 *
	 * Depending on the Xen version, pirq_needs_eoi might return true
	 * not only for level triggered interrupts but for edge triggered
	 * interrupts too. In any case Xen always honors the eoi mechanism,
	 * not injecting any more pirqs of the same kind if the first one
	 * hasn't received an eoi yet. Therefore using the fasteoi handler
	 * is the right choice either way.
	 */
	if (shareable)
		irq_set_chip_and_handler_name(irq, &xen_pirq_chip,
				handle_fasteoi_irq, name);
	else
		irq_set_chip_and_handler_name(irq, &xen_pirq_chip,
				handle_edge_irq, name);

out:
	mutex_unlock(&irq_mapping_update_lock);

	return irq;
}

#ifdef CONFIG_PCI_MSI
int xen_allocate_pirq_msi(struct pci_dev *dev, struct msi_desc *msidesc)
{
	int rc;
	struct physdev_get_free_pirq op_get_free_pirq;

	op_get_free_pirq.type = MAP_PIRQ_TYPE_MSI;
	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);

	WARN_ONCE(rc == -ENOSYS,
		  "hypervisor does not support the PHYSDEVOP_get_free_pirq interface\n");

	return rc ? -1 : op_get_free_pirq.pirq;
}

int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
			     int pirq, const char *name, domid_t domid)
{
	int irq, ret;

	mutex_lock(&irq_mapping_update_lock);

	irq = xen_allocate_irq_dynamic();
	if (irq < 0)
		goto out;

	irq_set_chip_and_handler_name(irq, &xen_pirq_chip, handle_edge_irq,
			name);

	ret = xen_irq_info_pirq_setup(irq, 0, pirq, 0, domid, 0);
	if (ret < 0)
		goto error_irq;
	ret = irq_set_msi_desc(irq, msidesc);
	if (ret < 0)
		goto error_irq;
out:
	mutex_unlock(&irq_mapping_update_lock);
	return irq;
error_irq:
	__unbind_from_irq(irq);
	mutex_unlock(&irq_mapping_update_lock);
	return ret;
}
#endif

int xen_destroy_irq(int irq)
{
	struct irq_desc *desc;
	struct physdev_unmap_pirq unmap_irq;
	struct irq_info *info = info_for_irq(irq);
	int rc = -ENOENT;

	mutex_lock(&irq_mapping_update_lock);

	desc = irq_to_desc(irq);
	if (!desc)
		goto out;

	if (xen_initial_domain()) {
		unmap_irq.pirq = info->u.pirq.pirq;
		unmap_irq.domid = info->u.pirq.domid;
		rc = HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq, &unmap_irq);
		/* If another domain quits without making the pci_disable_msix
		 * call, the Xen hypervisor takes care of freeing the PIRQs
		 * (free_domain_pirqs).
		 */
		if ((rc == -ESRCH && info->u.pirq.domid != DOMID_SELF))
			pr_info("domain %d does not have %d anymore\n",
				info->u.pirq.domid, info->u.pirq.pirq);
		else if (rc) {
			pr_warn("unmap irq failed %d\n", rc);
			goto out;
		}
	}

	xen_free_irq(irq);

out:
	mutex_unlock(&irq_mapping_update_lock);
	return rc;
}

int xen_irq_from_pirq(unsigned pirq)
{
	int irq;

	struct irq_info *info;

	mutex_lock(&irq_mapping_update_lock);

	list_for_each_entry(info, &xen_irq_list_head, list) {
		if (info->type != IRQT_PIRQ)
			continue;
		irq = info->irq;
		if (info->u.pirq.pirq == pirq)
			goto out;
	}
	irq = -1;
out:
	mutex_unlock(&irq_mapping_update_lock);

	return irq;
}


int xen_pirq_from_irq(unsigned irq)
{
	return pirq_from_irq(irq);
}
EXPORT_SYMBOL_GPL(xen_pirq_from_irq);

int bind_evtchn_to_irq(unsigned int evtchn)
{
	int irq;
	int ret;

	if (evtchn >= xen_evtchn_max_channels())
		return -ENOMEM;

	mutex_lock(&irq_mapping_update_lock);

	irq = get_evtchn_to_irq(evtchn);

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

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

		ret = xen_irq_info_evtchn_setup(irq, evtchn);
		if (ret < 0) {
			__unbind_from_irq(irq);
			irq = ret;
			goto out;
		}
	} else {
		struct irq_info *info = info_for_irq(irq);
		WARN_ON(info == NULL || info->type != IRQT_EVTCHN);
	}

out:
	mutex_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;
	int ret;

	mutex_lock(&irq_mapping_update_lock);

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

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

		irq_set_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;

		ret = xen_irq_info_ipi_setup(cpu, irq, evtchn, ipi);
		if (ret < 0) {
			__unbind_from_irq(irq);
			irq = ret;
			goto out;
		}
		bind_evtchn_to_cpu(evtchn, cpu);
	} else {
		struct irq_info *info = info_for_irq(irq);
		WARN_ON(info == NULL || info->type != IRQT_IPI);
	}

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

static int bind_interdomain_evtchn_to_irq(unsigned int remote_domain,
					  unsigned int remote_port)
{
	struct evtchn_bind_interdomain bind_interdomain;
	int err;

	bind_interdomain.remote_dom  = remote_domain;
	bind_interdomain.remote_port = remote_port;

	err = HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain,
					  &bind_interdomain);

	return err ? : bind_evtchn_to_irq(bind_interdomain.local_port);
}

static int find_virq(unsigned int virq, unsigned int cpu)
{
	struct evtchn_status status;
	int port, rc = -ENOENT;

	memset(&status, 0, sizeof(status));
	for (port = 0; port < xen_evtchn_max_channels(); port++) {
		status.dom = DOMID_SELF;
		status.port = port;
		rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
		if (rc < 0)
			continue;
		if (status.status != EVTCHNSTAT_virq)
			continue;
		if (status.u.virq == virq && status.vcpu == cpu) {
			rc = port;
			break;
		}
	}
	return rc;
}

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

	mutex_lock(&irq_mapping_update_lock);

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

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

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

		bind_virq.virq = virq;
		bind_virq.vcpu = cpu;
		ret = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
						&bind_virq);
		if (ret == 0)
			evtchn = bind_virq.port;
		else {
			if (ret == -EEXIST)
				ret = find_virq(virq, cpu);
			BUG_ON(ret < 0);
			evtchn = ret;
		}

		ret = xen_irq_info_virq_setup(cpu, irq, evtchn, virq);
		if (ret < 0) {
			__unbind_from_irq(irq);
			irq = ret;
			goto out;
		}

		bind_evtchn_to_cpu(evtchn, cpu);
	} else {
		struct irq_info *info = info_for_irq(irq);
		WARN_ON(info == NULL || info->type != IRQT_VIRQ);
	}

out:
	mutex_unlock(&irq_mapping_update_lock);

	return irq;
}

static void unbind_from_irq(unsigned int irq)
{
	mutex_lock(&irq_mapping_update_lock);
	__unbind_from_irq(irq);
	mutex_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)
{
	int irq, retval;

	irq = bind_evtchn_to_irq(evtchn);
	if (irq < 0)
		return irq;
	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_interdomain_evtchn_to_irqhandler(unsigned int remote_domain,
					  unsigned int remote_port,
					  irq_handler_t handler,
					  unsigned long irqflags,
					  const char *devname,
					  void *dev_id)
{
	int irq, retval;

	irq = bind_interdomain_evtchn_to_irq(remote_domain, remote_port);
	if (irq < 0)
		return irq;

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

	return irq;
}
EXPORT_SYMBOL_GPL(bind_interdomain_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)
{
	int irq, retval;

	irq = bind_virq_to_irq(virq, cpu);
	if (irq < 0)
		return irq;
	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 | IRQF_FORCE_RESUME | IRQF_EARLY_RESUME;
	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)
{
	struct irq_info *info = irq_get_handler_data(irq);

	if (WARN_ON(!info))
		return;
	free_irq(irq, dev_id);
	unbind_from_irq(irq);
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);

int evtchn_make_refcounted(unsigned int evtchn)
{
	int irq = get_evtchn_to_irq(evtchn);
	struct irq_info *info;

	if (irq == -1)
		return -ENOENT;

	info = irq_get_handler_data(irq);

	if (!info)
		return -ENOENT;

	WARN_ON(info->refcnt != -1);

	info->refcnt = 1;

	return 0;
}
EXPORT_SYMBOL_GPL(evtchn_make_refcounted);

int evtchn_get(unsigned int evtchn)
{
	int irq;
	struct irq_info *info;
	int err = -ENOENT;

	if (evtchn >= xen_evtchn_max_channels())
		return -EINVAL;

	mutex_lock(&irq_mapping_update_lock);

	irq = get_evtchn_to_irq(evtchn);
	if (irq == -1)
		goto done;

	info = irq_get_handler_data(irq);

	if (!info)
		goto done;

	err = -EINVAL;
	if (info->refcnt <= 0)
		goto done;

	info->refcnt++;
	err = 0;
 done:
	mutex_unlock(&irq_mapping_update_lock);

	return err;
}
EXPORT_SYMBOL_GPL(evtchn_get);

void evtchn_put(unsigned int evtchn)
{
	int irq = get_evtchn_to_irq(evtchn);
	if (WARN_ON(irq == -1))
		return;
	unbind_from_irq(irq);
}
EXPORT_SYMBOL_GPL(evtchn_put);

void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
	int irq;

#ifdef CONFIG_X86
	if (unlikely(vector == XEN_NMI_VECTOR)) {
		int rc =  HYPERVISOR_vcpu_op(VCPUOP_send_nmi, cpu, NULL);
		if (rc < 0)
			printk(KERN_WARNING "Sending nmi to CPU%d failed (rc:%d)\n", cpu, rc);
		return;
	}
#endif
	irq = per_cpu(ipi_to_irq, cpu)[vector];
	BUG_ON(irq < 0);
	notify_remote_via_irq(irq);
}

static DEFINE_PER_CPU(unsigned, xed_nesting_count);

static void __xen_evtchn_do_upcall(void)
{
	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
	int cpu = get_cpu();
	unsigned count;

	do {
		vcpu_info->evtchn_upcall_pending = 0;

		if (__this_cpu_inc_return(xed_nesting_count) - 1)
			goto out;

		xen_evtchn_handle_events(cpu);

		BUG_ON(!irqs_disabled());

		count = __this_cpu_read(xed_nesting_count);
		__this_cpu_write(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);

	irq_enter();
#ifdef CONFIG_X86
	exit_idle();
#endif

	__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);

	if (WARN_ON(!info))
		return;

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

	mutex_lock(&irq_mapping_update_lock);

	/* After resume the irq<->evtchn mappings are all cleared out */
	BUG_ON(get_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);

	(void)xen_irq_info_evtchn_setup(irq, evtchn);

	mutex_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);
	int masked;

	if (!VALID_EVTCHN(evtchn))
		return -1;

	/*
	 * Events delivered via platform PCI interrupts are always
	 * routed to vcpu 0 and hence cannot be rebound.
	 */
	if (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;

	/*
	 * Mask the event while changing the VCPU binding to prevent
	 * it being delivered on an unexpected VCPU.
	 */
	masked = test_and_set_mask(evtchn);

	/*
	 * 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);

	if (!masked)
		unmask_evtchn(evtchn);

	return 0;
}

static int set_affinity_irq(struct irq_data *data, const struct cpumask *dest,
			    bool force)
{
	unsigned tcpu = cpumask_first(dest);

	return rebind_irq_to_cpu(data->irq, tcpu);
}

static int retrigger_evtchn(int evtchn)
{
	int masked;

	if (!VALID_EVTCHN(evtchn))
		return 0;

	masked = test_and_set_mask(evtchn);
	set_evtchn(evtchn);
	if (!masked)
		unmask_evtchn(evtchn);

	return 1;
}

int resend_irq_on_evtchn(unsigned int irq)
{
	return retrigger_evtchn(evtchn_from_irq(irq));
}

static void enable_dynirq(struct irq_data *data)
{
	int evtchn = evtchn_from_irq(data->irq);

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

static void disable_dynirq(struct irq_data *data)
{
	int evtchn = evtchn_from_irq(data->irq);

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

static void ack_dynirq(struct irq_data *data)
{
	int evtchn = evtchn_from_irq(data->irq);

	irq_move_irq(data);

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

static void mask_ack_dynirq(struct irq_data *data)
{
	disable_dynirq(data);
	ack_dynirq(data);
}

static int retrigger_dynirq(struct irq_data *data)
{
	return retrigger_evtchn(evtchn_from_irq(data->irq));
}

static void restore_pirqs(void)
{
	int pirq, rc, irq, gsi;
	struct physdev_map_pirq map_irq;
	struct irq_info *info;

	list_for_each_entry(info, &xen_irq_list_head, list) {
		if (info->type != IRQT_PIRQ)
			continue;

		pirq = info->u.pirq.pirq;
		gsi = info->u.pirq.gsi;
		irq = info->irq;

		/* save/restore of PT devices doesn't work, so at this point the
		 * only devices present are GSI based emulated devices */
		if (!gsi)
			continue;

		map_irq.domid = DOMID_SELF;
		map_irq.type = MAP_PIRQ_TYPE_GSI;
		map_irq.index = gsi;
		map_irq.pirq = pirq;

		rc = HYPERVISOR_physdev_op(PHYSDEVOP_map_pirq, &map_irq);
		if (rc) {
			pr_warn("xen map irq failed gsi=%d irq=%d pirq=%d rc=%d\n",
				gsi, irq, pirq, rc);
			xen_free_irq(irq);
			continue;
		}

		printk(KERN_DEBUG "xen: --> irq=%d, pirq=%d\n", irq, map_irq.pirq);

		__startup_pirq(irq);
	}
}

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. */
		(void)xen_irq_info_virq_setup(cpu, irq, evtchn, virq);
		bind_evtchn_to_cpu(evtchn, cpu);
	}
}

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. */
		(void)xen_irq_info_ipi_setup(cpu, irq, evtchn, ipi);
		bind_evtchn_to_cpu(evtchn, cpu);
	}
}

/* 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);
}
EXPORT_SYMBOL(xen_clear_irq_pending);
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 with timeout.  In the usual case,
 * the irq will be disabled so it won't deliver an interrupt. */
void xen_poll_irq_timeout(int irq, u64 timeout)
{
	evtchn_port_t evtchn = evtchn_from_irq(irq);

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

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

		if (HYPERVISOR_sched_op(SCHEDOP_poll, &poll) != 0)
			BUG();
	}
}
EXPORT_SYMBOL(xen_poll_irq_timeout);
/* 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)
{
	xen_poll_irq_timeout(irq, 0 /* no timeout */);
}

/* Check whether the IRQ line is shared with other guests. */
int xen_test_irq_shared(int irq)
{
	struct irq_info *info = info_for_irq(irq);
	struct physdev_irq_status_query irq_status;

	if (WARN_ON(!info))
		return -ENOENT;

	irq_status.irq = info->u.pirq.pirq;

	if (HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status))
		return 0;
	return !(irq_status.flags & XENIRQSTAT_shared);
}
EXPORT_SYMBOL_GPL(xen_test_irq_shared);

void xen_irq_resume(void)
{
	unsigned int cpu;
	struct irq_info *info;

	/* New event-channel space is not 'live' yet. */
	xen_evtchn_mask_all();

	/* No IRQ <-> event-channel mappings. */
	list_for_each_entry(info, &xen_irq_list_head, list)
		info->evtchn = 0; /* zap event-channel binding */

	clear_evtchn_to_irq_all();

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

	restore_pirqs();
}

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

	.irq_disable		= disable_dynirq,
	.irq_mask		= disable_dynirq,
	.irq_unmask		= enable_dynirq,

	.irq_ack		= ack_dynirq,
	.irq_mask_ack		= mask_ack_dynirq,

	.irq_set_affinity	= set_affinity_irq,
	.irq_retrigger		= retrigger_dynirq,
};

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

	.irq_startup		= startup_pirq,
	.irq_shutdown		= shutdown_pirq,
	.irq_enable		= enable_pirq,
	.irq_disable		= disable_pirq,

	.irq_mask		= disable_dynirq,
	.irq_unmask		= enable_dynirq,

	.irq_ack		= eoi_pirq,
	.irq_eoi		= eoi_pirq,
	.irq_mask_ack		= mask_ack_pirq,

	.irq_set_affinity	= set_affinity_irq,

	.irq_retrigger		= retrigger_dynirq,
};

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

	.irq_disable		= disable_dynirq,
	.irq_mask		= disable_dynirq,
	.irq_unmask		= enable_dynirq,

	.irq_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(HYPERVISOR_CALLBACK_VECTOR);
		rc = xen_set_callback_via(callback_via);
		if (rc) {
			pr_err("Request for Xen HVM callback vector failed\n");
			xen_have_vector_callback = 0;
			return;
		}
		pr_info("Xen HVM callback vector for event delivery is enabled\n");
		/* in the restore case the vector has already been allocated */
		if (!test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors))
			alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
					xen_hvm_callback_vector);
	}
}
#else
void xen_callback_vector(void) {}
#endif

void __init xen_init_IRQ(void)
{
	xen_evtchn_2l_init();

	evtchn_to_irq = kcalloc(EVTCHN_ROW(xen_evtchn_max_channels()),
				sizeof(*evtchn_to_irq), GFP_KERNEL);
	BUG_ON(!evtchn_to_irq);

	/* No event channels are 'live' right now. */
	xen_evtchn_mask_all();

	pirq_needs_eoi = pirq_needs_eoi_flag;

#ifdef CONFIG_X86
	if (xen_hvm_domain()) {
		xen_callback_vector();
		native_init_IRQ();
		/* pci_xen_hvm_init must be called after native_init_IRQ so that
		 * __acpi_register_gsi can point at the right function */
		pci_xen_hvm_init();
	} else {
		int rc;
		struct physdev_pirq_eoi_gmfn eoi_gmfn;

		irq_ctx_init(smp_processor_id());
		if (xen_initial_domain())
			pci_xen_initial_domain();

		pirq_eoi_map = (void *)__get_free_page(GFP_KERNEL|__GFP_ZERO);
		eoi_gmfn.gmfn = virt_to_mfn(pirq_eoi_map);
		rc = HYPERVISOR_physdev_op(PHYSDEVOP_pirq_eoi_gmfn_v2, &eoi_gmfn);
		if (rc != 0) {
			free_page((unsigned long) pirq_eoi_map);
			pirq_eoi_map = NULL;
		} else
			pirq_needs_eoi = pirq_check_eoi_map;
	}
#endif
}