/*
 * 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 <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, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};

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

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;
}
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;

                dynamic_irq_init(irq);
                set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
                                              handle_level_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_irq_info(IRQT_IPI, ipi, evtchn);

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

                bind_evtchn_to_cpu(evtchn, cpu);
        }

        irq_bindcount[irq]++;

 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();

                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,
                              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;

        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_evtchn[i], i,
                                evtchn_to_irq[i]);
                }
        }

        spin_unlock_irqrestore(&debug_lock, flags);

        return IRQ_HANDLED;
}


/*
 * 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.
 */
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);
        static DEFINE_PER_CPU(unsigned, nesting_count);
        unsigned count;

        do {
                unsigned long pending_words;

                vcpu_info->evtchn_upcall_pending = 0;

                if (__get_cpu_var(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];

                                if (irq != -1)
                                        xen_do_IRQ(irq, regs);
                        }
                }

                BUG_ON(!irqs_disabled());

                count = __get_cpu_var(nesting_count);
                __get_cpu_var(nesting_count) = 0;
        } while(count != 1);

out:
        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);
}

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 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());
}