xen: event channels

obj-y		:= enlighten.o setup.o features.o multicalls.o mmu.o

obj-y		:= enlighten.o setup.o features.o multicalls.o mmu.o \

			events.o

	.memory_setup = xen_memory_setup,

	.arch_setup = xen_arch_setup,

	.init_IRQ = xen_init_IRQ,

	.cpuid = xen_cpuid,

/*

 * 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 <asm/ptrace.h>

#include <asm/irq.h>

#include <asm/sync_bitops.h>

#include <asm/xen/hypercall.h>

#include <xen/events.h>

#include <xen/interface/xen.h>

#include <xen/interface/event_channel.h>

#include "xen-ops.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, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};

/* Packed IRQ information: binding type, sub-type index, and event channel. */

struct packed_irq

{

	unsigned short evtchn;

	unsigned char index;

	unsigned char type;

};

static struct packed_irq irq_info[NR_IRQS];

/* Binding types. */

enum { IRQT_UNBOUND, IRQT_PIRQ, IRQT_VIRQ, IRQT_IPI, IRQT_EVTCHN };

/* Convenient shorthand for packed representation of an unbound IRQ. */

#define IRQ_UNBOUND	mk_irq_info(IRQT_UNBOUND, 0, 0)

static int evtchn_to_irq[NR_EVENT_CHANNELS] = {

	[0 ... NR_EVENT_CHANNELS-1] = -1

};

static unsigned long cpu_evtchn_mask[NR_CPUS][NR_EVENT_CHANNELS/BITS_PER_LONG];

static u8 cpu_evtchn[NR_EVENT_CHANNELS];

/* Reference counts for bindings to IRQs. */

static int irq_bindcount[NR_IRQS];

/* Xen will never allocate port zero for any purpose. */

#define VALID_EVTCHN(chn)	((chn) != 0)

/*

 * 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 force_evtchn_callback(void)

{

	(void)HYPERVISOR_xen_version(0, NULL);

}

EXPORT_SYMBOL_GPL(force_evtchn_callback);

static struct irq_chip xen_dynamic_chip;

/* Constructor for packed IRQ information. */

static inline struct packed_irq mk_irq_info(u32 type, u32 index, u32 evtchn)

{

	return (struct packed_irq) { evtchn, index, type };

}

/*

 * Accessors for packed IRQ information.

 */

static inline unsigned int evtchn_from_irq(int irq)

{

	return irq_info[irq].evtchn;

}

static inline unsigned int index_from_irq(int irq)

{

	return irq_info[irq].index;

}

static inline unsigned int type_from_irq(int irq)

{

	return irq_info[irq].type;

}

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

	irq_desc[irq].affinity = cpumask_of_cpu(cpu);

#endif

	__clear_bit(chn, cpu_evtchn_mask[cpu_evtchn[chn]]);

	__set_bit(chn, cpu_evtchn_mask[cpu]);

	cpu_evtchn[chn] = cpu;

}

static void init_evtchn_cpu_bindings(void)

{

#ifdef CONFIG_SMP

	int i;

	/* By default all event channels notify CPU#0. */

	for (i = 0; i < NR_IRQS; i++)

		irq_desc[i].affinity = cpumask_of_cpu(0);

#endif

	memset(cpu_evtchn, 0, sizeof(cpu_evtchn));

	memset(cpu_evtchn_mask[0], ~0, sizeof(cpu_evtchn_mask[0]));

}

static inline unsigned int cpu_from_evtchn(unsigned int evtchn)

{

	return cpu_evtchn[evtchn];

}

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]);

}

/**

 * 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)

{

	int irq;

	/* Only allocate from dynirq range */

	for (irq = 0; irq < NR_IRQS; irq++)

		if (irq_bindcount[irq] == 0)

			break;

	if (irq == NR_IRQS)

		panic("No available IRQ to bind to: increase NR_IRQS!\n");

	return irq;

}

static 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();

		dynamic_irq_init(irq);

		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,

					      handle_level_irq, "event");

		evtchn_to_irq[evtchn] = irq;

		irq_info[irq] = mk_irq_info(IRQT_EVTCHN, 0, evtchn);

	}

	irq_bindcount[irq]++;

	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();

		dynamic_irq_init(irq);

		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,

					      handle_level_irq, "virq");

		evtchn_to_irq[evtchn] = irq;

		irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);

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

		bind_evtchn_to_cpu(evtchn, cpu);

	}

	irq_bindcount[irq]++;

	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) && (--irq_bindcount[irq] == 0)) {

		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))

				[index_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;

		irq_info[irq] = IRQ_UNBOUND;

		dynamic_irq_init(irq);

	}

	spin_unlock(&irq_mapping_update_lock);

}

int bind_evtchn_to_irqhandler(unsigned int evtchn,

			      irqreturn_t (*handler)(int, void *),

			      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,

			    irqreturn_t (*handler)(int, void *),

			    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);

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);

/*

 * 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.

 */

fastcall void xen_evtchn_do_upcall(struct pt_regs *regs)

{

	int cpu = get_cpu();

	struct shared_info *s = HYPERVISOR_shared_info;

	struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);

	unsigned long pending_words;

	vcpu_info->evtchn_upcall_pending = 0;

	/* NB. No need for a barrier here -- XCHG is a barrier on x86. */

	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];

			if (irq != -1) {

				regs->orig_eax = ~irq;

				do_IRQ(regs);

			}

		}

	}

	put_cpu();

}

/* Rebind an evtchn so that it gets delivered to a specific cpu */

static void rebind_irq_to_cpu(unsigned irq, unsigned tcpu)

{

	struct evtchn_bind_vcpu bind_vcpu;

	int evtchn = evtchn_from_irq(irq);

	if (!VALID_EVTCHN(evtchn))

		return;

	/* 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);

}

static void set_affinity_irq(unsigned irq, cpumask_t dest)

{

	unsigned tcpu = first_cpu(dest);

	rebind_irq_to_cpu(irq, tcpu);

}

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);

	int ret = 0;

	if (VALID_EVTCHN(evtchn)) {

		set_evtchn(evtchn);

		ret = 1;

	}

	return ret;

}

static struct irq_chip xen_dynamic_chip __read_mostly = {

	.name		= "xen-dyn",

	.mask		= disable_dynirq,

	.unmask		= enable_dynirq,

	.ack		= ack_dynirq,

	.set_affinity	= set_affinity_irq,

	.retrigger	= retrigger_dynirq,

};

void __init xen_init_IRQ(void)

{

	int i;

	init_evtchn_cpu_bindings();

	/* No event channels are 'live' right now. */

	for (i = 0; i < NR_EVENT_CHANNELS; i++)

		mask_evtchn(i);

	/* Dynamic IRQ space is currently unbound. Zero the refcnts. */

	for (i = 0; i < NR_IRQS; i++)

		irq_bindcount[i] = 0;

	irq_ctx_init(smp_processor_id());

}

#ifndef _XEN_EVENTS_H

#define _XEN_EVENTS_H

#include <linux/irq.h>

int bind_evtchn_to_irqhandler(unsigned int evtchn,

			      irqreturn_t (*handler)(int, void *),

			      unsigned long irqflags, const char *devname,

			      void *dev_id);

int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,

			    irqreturn_t (*handler)(int, void *),

			    unsigned long irqflags, const char *devname, void *dev_id);

/*

 * Common unbind function for all event sources. Takes IRQ to unbind from.

 * Automatically closes the underlying event channel (even for bindings

 * made with bind_evtchn_to_irqhandler()).

 */

void unbind_from_irqhandler(unsigned int irq, void *dev_id);

static inline void notify_remote_via_evtchn(int port)

{

	struct evtchn_send send = { .port = port };

	(void)HYPERVISOR_event_channel_op(EVTCHNOP_send, &send);

}

extern void notify_remote_via_irq(int irq);

#endif	/* _XEN_EVENTS_H */