path: root/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. Hardware interrupts. Not supported at present.
 *
 * 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/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-ops.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>

/*
 * 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 short vector;
		} pirq;
	} u;
};

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;

/* 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 =