xtensa: support DMA buffers in high memory

[cris-mirror.git] / virt / kvm / arm / vgic / vgic.c

/*
 * Copyright (C) 2015, 2016 ARM Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/list_sort.h>
#include <linux/interrupt.h>
#include <linux/irq.h>

#include "vgic.h"

#define CREATE_TRACE_POINTS
#include "trace.h"

#ifdef CONFIG_DEBUG_SPINLOCK
#define DEBUG_SPINLOCK_BUG_ON(p) BUG_ON(p)
#else
#define DEBUG_SPINLOCK_BUG_ON(p)
#endif

struct vgic_global kvm_vgic_global_state __ro_after_init = {
        .gicv3_cpuif = STATIC_KEY_FALSE_INIT,
};

/*
 * Locking order is always:
 * kvm->lock (mutex)
 *   its->cmd_lock (mutex)
 *     its->its_lock (mutex)
 *       vgic_cpu->ap_list_lock
 *         kvm->lpi_list_lock
 *           vgic_irq->irq_lock
 *
 * If you need to take multiple locks, always take the upper lock first,
 * then the lower ones, e.g. first take the its_lock, then the irq_lock.
 * If you are already holding a lock and need to take a higher one, you
 * have to drop the lower ranking lock first and re-aquire it after having
 * taken the upper one.
 *
 * When taking more than one ap_list_lock at the same time, always take the
 * lowest numbered VCPU's ap_list_lock first, so:
 *   vcpuX->vcpu_id < vcpuY->vcpu_id:
 *     spin_lock(vcpuX->arch.vgic_cpu.ap_list_lock);
 *     spin_lock(vcpuY->arch.vgic_cpu.ap_list_lock);
 *
 * Since the VGIC must support injecting virtual interrupts from ISRs, we have
 * to use the spin_lock_irqsave/spin_unlock_irqrestore versions of outer
 * spinlocks for any lock that may be taken while injecting an interrupt.
 */

/*
 * Iterate over the VM's list of mapped LPIs to find the one with a
 * matching interrupt ID and return a reference to the IRQ structure.
 */
static struct vgic_irq *vgic_get_lpi(struct kvm *kvm, u32 intid)
{
        struct vgic_dist *dist = &kvm->arch.vgic;
        struct vgic_irq *irq = NULL;

        spin_lock(&dist->lpi_list_lock);

        list_for_each_entry(irq, &dist->lpi_list_head, lpi_list) {
                if (irq->intid != intid)
                        continue;

                /*
                 * This increases the refcount, the caller is expected to
                 * call vgic_put_irq() later once it's finished with the IRQ.
                 */
                vgic_get_irq_kref(irq);
                goto out_unlock;
        }
        irq = NULL;

out_unlock:
        spin_unlock(&dist->lpi_list_lock);

        return irq;
}

/*
 * This looks up the virtual interrupt ID to get the corresponding
 * struct vgic_irq. It also increases the refcount, so any caller is expected
 * to call vgic_put_irq() once it's finished with this IRQ.
 */
struct vgic_irq *vgic_get_irq(struct kvm *kvm, struct kvm_vcpu *vcpu,
                              u32 intid)
{
        /* SGIs and PPIs */
        if (intid <= VGIC_MAX_PRIVATE)
                return &vcpu->arch.vgic_cpu.private_irqs[intid];

        /* SPIs */
        if (intid <= VGIC_MAX_SPI)
                return &kvm->arch.vgic.spis[intid - VGIC_NR_PRIVATE_IRQS];

        /* LPIs */
        if (intid >= VGIC_MIN_LPI)
                return vgic_get_lpi(kvm, intid);

        WARN(1, "Looking up struct vgic_irq for reserved INTID");
        return NULL;
}

/*
 * We can't do anything in here, because we lack the kvm pointer to
 * lock and remove the item from the lpi_list. So we keep this function
 * empty and use the return value of kref_put() to trigger the freeing.
 */
static void vgic_irq_release(struct kref *ref)
{
}

void vgic_put_irq(struct kvm *kvm, struct vgic_irq *irq)
{
        struct vgic_dist *dist = &kvm->arch.vgic;

        if (irq->intid < VGIC_MIN_LPI)
                return;

        spin_lock(&dist->lpi_list_lock);
        if (!kref_put(&irq->refcount, vgic_irq_release)) {
                spin_unlock(&dist->lpi_list_lock);
                return;
        };

        list_del(&irq->lpi_list);
        dist->lpi_list_count--;
        spin_unlock(&dist->lpi_list_lock);

        kfree(irq);
}

void vgic_irq_set_phys_pending(struct vgic_irq *irq, bool pending)
{
        WARN_ON(irq_set_irqchip_state(irq->host_irq,
                                      IRQCHIP_STATE_PENDING,
                                      pending));
}

bool vgic_get_phys_line_level(struct vgic_irq *irq)
{
        bool line_level;

        BUG_ON(!irq->hw);

        if (irq->get_input_level)
                return irq->get_input_level(irq->intid);

        WARN_ON(irq_get_irqchip_state(irq->host_irq,
                                      IRQCHIP_STATE_PENDING,
                                      &line_level));
        return line_level;
}

/* Set/Clear the physical active state */
void vgic_irq_set_phys_active(struct vgic_irq *irq, bool active)
{

        BUG_ON(!irq->hw);
        WARN_ON(irq_set_irqchip_state(irq->host_irq,
                                      IRQCHIP_STATE_ACTIVE,
                                      active));
}

/**
 * kvm_vgic_target_oracle - compute the target vcpu for an irq
 *
 * @irq:        The irq to route. Must be already locked.
 *
 * Based on the current state of the interrupt (enabled, pending,
 * active, vcpu and target_vcpu), compute the next vcpu this should be
 * given to. Return NULL if this shouldn't be injected at all.
 *
 * Requires the IRQ lock to be held.
 */
static struct kvm_vcpu *vgic_target_oracle(struct vgic_irq *irq)
{
        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));

        /* If the interrupt is active, it must stay on the current vcpu */
        if (irq->active)
                return irq->vcpu ? : irq->target_vcpu;

        /*
         * If the IRQ is not active but enabled and pending, we should direct
         * it to its configured target VCPU.
         * If the distributor is disabled, pending interrupts shouldn't be
         * forwarded.
         */
        if (irq->enabled && irq_is_pending(irq)) {
                if (unlikely(irq->target_vcpu &&
                             !irq->target_vcpu->kvm->arch.vgic.enabled))
                        return NULL;

                return irq->target_vcpu;
        }

        /* If neither active nor pending and enabled, then this IRQ should not
         * be queued to any VCPU.
         */
        return NULL;
}

/*
 * The order of items in the ap_lists defines how we'll pack things in LRs as
 * well, the first items in the list being the first things populated in the
 * LRs.
 *
 * A hard rule is that active interrupts can never be pushed out of the LRs
 * (and therefore take priority) since we cannot reliably trap on deactivation
 * of IRQs and therefore they have to be present in the LRs.
 *
 * Otherwise things should be sorted by the priority field and the GIC
 * hardware support will take care of preemption of priority groups etc.
 *
 * Return negative if "a" sorts before "b", 0 to preserve order, and positive
 * to sort "b" before "a".
 */
static int vgic_irq_cmp(void *priv, struct list_head *a, struct list_head *b)
{
        struct vgic_irq *irqa = container_of(a, struct vgic_irq, ap_list);
        struct vgic_irq *irqb = container_of(b, struct vgic_irq, ap_list);
        bool penda, pendb;
        int ret;

        spin_lock(&irqa->irq_lock);
        spin_lock_nested(&irqb->irq_lock, SINGLE_DEPTH_NESTING);

        if (irqa->active || irqb->active) {
                ret = (int)irqb->active - (int)irqa->active;
                goto out;
        }

        penda = irqa->enabled && irq_is_pending(irqa);
        pendb = irqb->enabled && irq_is_pending(irqb);

        if (!penda || !pendb) {
                ret = (int)pendb - (int)penda;
                goto out;
        }

        /* Both pending and enabled, sort by priority */
        ret = irqa->priority - irqb->priority;
out:
        spin_unlock(&irqb->irq_lock);
        spin_unlock(&irqa->irq_lock);
        return ret;
}

/* Must be called with the ap_list_lock held */
static void vgic_sort_ap_list(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;

        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vgic_cpu->ap_list_lock));

        list_sort(NULL, &vgic_cpu->ap_list_head, vgic_irq_cmp);
}

/*
 * Only valid injection if changing level for level-triggered IRQs or for a
 * rising edge, and in-kernel connected IRQ lines can only be controlled by
 * their owner.
 */
static bool vgic_validate_injection(struct vgic_irq *irq, bool level, void *owner)
{
        if (irq->owner != owner)
                return false;

        switch (irq->config) {
        case VGIC_CONFIG_LEVEL:
                return irq->line_level != level;
        case VGIC_CONFIG_EDGE:
                return level;
        }

        return false;
}

/*
 * Check whether an IRQ needs to (and can) be queued to a VCPU's ap list.
 * Do the queuing if necessary, taking the right locks in the right order.
 * Returns true when the IRQ was queued, false otherwise.
 *
 * Needs to be entered with the IRQ lock already held, but will return
 * with all locks dropped.
 */
bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq,
                           unsigned long flags)
{
        struct kvm_vcpu *vcpu;

        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));

retry:
        vcpu = vgic_target_oracle(irq);
        if (irq->vcpu || !vcpu) {
                /*
                 * If this IRQ is already on a VCPU's ap_list, then it
                 * cannot be moved or modified and there is no more work for
                 * us to do.
                 *
                 * Otherwise, if the irq is not pending and enabled, it does
                 * not need to be inserted into an ap_list and there is also
                 * no more work for us to do.
                 */
                spin_unlock_irqrestore(&irq->irq_lock, flags);

                /*
                 * We have to kick the VCPU here, because we could be
                 * queueing an edge-triggered interrupt for which we
                 * get no EOI maintenance interrupt. In that case,
                 * while the IRQ is already on the VCPU's AP list, the
                 * VCPU could have EOI'ed the original interrupt and
                 * won't see this one until it exits for some other
                 * reason.
                 */
                if (vcpu) {
                        kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
                        kvm_vcpu_kick(vcpu);
                }
                return false;
        }

        /*
         * We must unlock the irq lock to take the ap_list_lock where
         * we are going to insert this new pending interrupt.
         */
        spin_unlock_irqrestore(&irq->irq_lock, flags);

        /* someone can do stuff here, which we re-check below */

        spin_lock_irqsave(&vcpu->arch.vgic_cpu.ap_list_lock, flags);
        spin_lock(&irq->irq_lock);

        /*
         * Did something change behind our backs?
         *
         * There are two cases:
         * 1) The irq lost its pending state or was disabled behind our
         *    backs and/or it was queued to another VCPU's ap_list.
         * 2) Someone changed the affinity on this irq behind our
         *    backs and we are now holding the wrong ap_list_lock.
         *
         * In both cases, drop the locks and retry.
         */

        if (unlikely(irq->vcpu || vcpu != vgic_target_oracle(irq))) {
                spin_unlock(&irq->irq_lock);
                spin_unlock_irqrestore(&vcpu->arch.vgic_cpu.ap_list_lock, flags);

                spin_lock_irqsave(&irq->irq_lock, flags);
                goto retry;
        }

        /*
         * Grab a reference to the irq to reflect the fact that it is
         * now in the ap_list.
         */
        vgic_get_irq_kref(irq);
        list_add_tail(&irq->ap_list, &vcpu->arch.vgic_cpu.ap_list_head);
        irq->vcpu = vcpu;

        spin_unlock(&irq->irq_lock);
        spin_unlock_irqrestore(&vcpu->arch.vgic_cpu.ap_list_lock, flags);

        kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
        kvm_vcpu_kick(vcpu);

        return true;
}

/**
 * kvm_vgic_inject_irq - Inject an IRQ from a device to the vgic
 * @kvm:     The VM structure pointer
 * @cpuid:   The CPU for PPIs
 * @intid:   The INTID to inject a new state to.
 * @level:   Edge-triggered:  true:  to trigger the interrupt
 *                            false: to ignore the call
 *           Level-sensitive  true:  raise the input signal
 *                            false: lower the input signal
 * @owner:   The opaque pointer to the owner of the IRQ being raised to verify
 *           that the caller is allowed to inject this IRQ.  Userspace
 *           injections will have owner == NULL.
 *
 * The VGIC is not concerned with devices being active-LOW or active-HIGH for
 * level-sensitive interrupts.  You can think of the level parameter as 1
 * being HIGH and 0 being LOW and all devices being active-HIGH.
 */
int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
                        bool level, void *owner)
{
        struct kvm_vcpu *vcpu;
        struct vgic_irq *irq;
        unsigned long flags;
        int ret;

        trace_vgic_update_irq_pending(cpuid, intid, level);

        ret = vgic_lazy_init(kvm);
        if (ret)
                return ret;

        vcpu = kvm_get_vcpu(kvm, cpuid);
        if (!vcpu && intid < VGIC_NR_PRIVATE_IRQS)
                return -EINVAL;

        irq = vgic_get_irq(kvm, vcpu, intid);
        if (!irq)
                return -EINVAL;

        spin_lock_irqsave(&irq->irq_lock, flags);

        if (!vgic_validate_injection(irq, level, owner)) {
                /* Nothing to see here, move along... */
                spin_unlock_irqrestore(&irq->irq_lock, flags);
                vgic_put_irq(kvm, irq);
                return 0;
        }

        if (irq->config == VGIC_CONFIG_LEVEL)
                irq->line_level = level;
        else
                irq->pending_latch = true;

        vgic_queue_irq_unlock(kvm, irq, flags);
        vgic_put_irq(kvm, irq);

        return 0;
}

/* @irq->irq_lock must be held */
static int kvm_vgic_map_irq(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
                            unsigned int host_irq,
                            bool (*get_input_level)(int vindid))
{
        struct irq_desc *desc;
        struct irq_data *data;

        /*
         * Find the physical IRQ number corresponding to @host_irq
         */
        desc = irq_to_desc(host_irq);
        if (!desc) {
                kvm_err("%s: no interrupt descriptor\n", __func__);
                return -EINVAL;
        }
        data = irq_desc_get_irq_data(desc);
        while (data->parent_data)
                data = data->parent_data;

        irq->hw = true;
        irq->host_irq = host_irq;
        irq->hwintid = data->hwirq;
        irq->get_input_level = get_input_level;
        return 0;
}

/* @irq->irq_lock must be held */
static inline void kvm_vgic_unmap_irq(struct vgic_irq *irq)
{
        irq->hw = false;
        irq->hwintid = 0;
        irq->get_input_level = NULL;
}

int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, unsigned int host_irq,
                          u32 vintid, bool (*get_input_level)(int vindid))
{
        struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
        unsigned long flags;
        int ret;

        BUG_ON(!irq);

        spin_lock_irqsave(&irq->irq_lock, flags);
        ret = kvm_vgic_map_irq(vcpu, irq, host_irq, get_input_level);
        spin_unlock_irqrestore(&irq->irq_lock, flags);
        vgic_put_irq(vcpu->kvm, irq);

        return ret;
}

int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, unsigned int vintid)
{
        struct vgic_irq *irq;
        unsigned long flags;

        if (!vgic_initialized(vcpu->kvm))
                return -EAGAIN;

        irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
        BUG_ON(!irq);

        spin_lock_irqsave(&irq->irq_lock, flags);
        kvm_vgic_unmap_irq(irq);
        spin_unlock_irqrestore(&irq->irq_lock, flags);
        vgic_put_irq(vcpu->kvm, irq);

        return 0;
}

/**
 * kvm_vgic_set_owner - Set the owner of an interrupt for a VM
 *
 * @vcpu:   Pointer to the VCPU (used for PPIs)
 * @intid:  The virtual INTID identifying the interrupt (PPI or SPI)
 * @owner:  Opaque pointer to the owner
 *
 * Returns 0 if intid is not already used by another in-kernel device and the
 * owner is set, otherwise returns an error code.
 */
int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner)
{
        struct vgic_irq *irq;
        unsigned long flags;
        int ret = 0;

        if (!vgic_initialized(vcpu->kvm))
                return -EAGAIN;

        /* SGIs and LPIs cannot be wired up to any device */
        if (!irq_is_ppi(intid) && !vgic_valid_spi(vcpu->kvm, intid))
                return -EINVAL;

        irq = vgic_get_irq(vcpu->kvm, vcpu, intid);
        spin_lock_irqsave(&irq->irq_lock, flags);
        if (irq->owner && irq->owner != owner)
                ret = -EEXIST;
        else
                irq->owner = owner;
        spin_unlock_irqrestore(&irq->irq_lock, flags);

        return ret;
}

/**
 * vgic_prune_ap_list - Remove non-relevant interrupts from the list
 *
 * @vcpu: The VCPU pointer
 *
 * Go over the list of "interesting" interrupts, and prune those that we
 * won't have to consider in the near future.
 */
static void vgic_prune_ap_list(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
        struct vgic_irq *irq, *tmp;
        unsigned long flags;

retry:
        spin_lock_irqsave(&vgic_cpu->ap_list_lock, flags);

        list_for_each_entry_safe(irq, tmp, &vgic_cpu->ap_list_head, ap_list) {
                struct kvm_vcpu *target_vcpu, *vcpuA, *vcpuB;

                spin_lock(&irq->irq_lock);

                BUG_ON(vcpu != irq->vcpu);

                target_vcpu = vgic_target_oracle(irq);

                if (!target_vcpu) {
                        /*
                         * We don't need to process this interrupt any
                         * further, move it off the list.
                         */
                        list_del(&irq->ap_list);
                        irq->vcpu = NULL;
                        spin_unlock(&irq->irq_lock);

                        /*
                         * This vgic_put_irq call matches the
                         * vgic_get_irq_kref in vgic_queue_irq_unlock,
                         * where we added the LPI to the ap_list. As
                         * we remove the irq from the list, we drop
                         * also drop the refcount.
                         */
                        vgic_put_irq(vcpu->kvm, irq);
                        continue;
                }

                if (target_vcpu == vcpu) {
                        /* We're on the right CPU */
                        spin_unlock(&irq->irq_lock);
                        continue;
                }

                /* This interrupt looks like it has to be migrated. */

                spin_unlock(&irq->irq_lock);
                spin_unlock_irqrestore(&vgic_cpu->ap_list_lock, flags);

                /*
                 * Ensure locking order by always locking the smallest
                 * ID first.
                 */
                if (vcpu->vcpu_id < target_vcpu->vcpu_id) {
                        vcpuA = vcpu;
                        vcpuB = target_vcpu;
                } else {
                        vcpuA = target_vcpu;
                        vcpuB = vcpu;
                }

                spin_lock_irqsave(&vcpuA->arch.vgic_cpu.ap_list_lock, flags);
                spin_lock_nested(&vcpuB->arch.vgic_cpu.ap_list_lock,
                                 SINGLE_DEPTH_NESTING);
                spin_lock(&irq->irq_lock);

                /*
                 * If the affinity has been preserved, move the
                 * interrupt around. Otherwise, it means things have
                 * changed while the interrupt was unlocked, and we
                 * need to replay this.
                 *
                 * In all cases, we cannot trust the list not to have
                 * changed, so we restart from the beginning.
                 */
                if (target_vcpu == vgic_target_oracle(irq)) {
                        struct vgic_cpu *new_cpu = &target_vcpu->arch.vgic_cpu;

                        list_del(&irq->ap_list);
                        irq->vcpu = target_vcpu;
                        list_add_tail(&irq->ap_list, &new_cpu->ap_list_head);
                }

                spin_unlock(&irq->irq_lock);
                spin_unlock(&vcpuB->arch.vgic_cpu.ap_list_lock);
                spin_unlock_irqrestore(&vcpuA->arch.vgic_cpu.ap_list_lock, flags);
                goto retry;
        }

        spin_unlock_irqrestore(&vgic_cpu->ap_list_lock, flags);
}

static inline void vgic_fold_lr_state(struct kvm_vcpu *vcpu)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_fold_lr_state(vcpu);
        else
                vgic_v3_fold_lr_state(vcpu);
}

/* Requires the irq_lock to be held. */
static inline void vgic_populate_lr(struct kvm_vcpu *vcpu,
                                    struct vgic_irq *irq, int lr)
{
        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&irq->irq_lock));

        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_populate_lr(vcpu, irq, lr);
        else
                vgic_v3_populate_lr(vcpu, irq, lr);
}

static inline void vgic_clear_lr(struct kvm_vcpu *vcpu, int lr)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_clear_lr(vcpu, lr);
        else
                vgic_v3_clear_lr(vcpu, lr);
}

static inline void vgic_set_underflow(struct kvm_vcpu *vcpu)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_set_underflow(vcpu);
        else
                vgic_v3_set_underflow(vcpu);
}

/* Requires the ap_list_lock to be held. */
static int compute_ap_list_depth(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
        struct vgic_irq *irq;
        int count = 0;

        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vgic_cpu->ap_list_lock));

        list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) {
                spin_lock(&irq->irq_lock);
                /* GICv2 SGIs can count for more than one... */
                if (vgic_irq_is_sgi(irq->intid) && irq->source)
                        count += hweight8(irq->source);
                else
                        count++;
                spin_unlock(&irq->irq_lock);
        }
        return count;
}

/* Requires the VCPU's ap_list_lock to be held. */
static void vgic_flush_lr_state(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
        struct vgic_irq *irq;
        int count = 0;

        DEBUG_SPINLOCK_BUG_ON(!spin_is_locked(&vgic_cpu->ap_list_lock));

        if (compute_ap_list_depth(vcpu) > kvm_vgic_global_state.nr_lr)
                vgic_sort_ap_list(vcpu);

        list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) {
                spin_lock(&irq->irq_lock);

                if (unlikely(vgic_target_oracle(irq) != vcpu))
                        goto next;

                /*
                 * If we get an SGI with multiple sources, try to get
                 * them in all at once.
                 */
                do {
                        vgic_populate_lr(vcpu, irq, count++);
                } while (irq->source && count < kvm_vgic_global_state.nr_lr);

next:
                spin_unlock(&irq->irq_lock);

                if (count == kvm_vgic_global_state.nr_lr) {
                        if (!list_is_last(&irq->ap_list,
                                          &vgic_cpu->ap_list_head))
                                vgic_set_underflow(vcpu);
                        break;
                }
        }

        vcpu->arch.vgic_cpu.used_lrs = count;

        /* Nuke remaining LRs */
        for ( ; count < kvm_vgic_global_state.nr_lr; count++)
                vgic_clear_lr(vcpu, count);
}

/* Sync back the hardware VGIC state into our emulation after a guest's run. */
void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;

        WARN_ON(vgic_v4_sync_hwstate(vcpu));

        /* An empty ap_list_head implies used_lrs == 0 */
        if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head))
                return;

        if (vgic_cpu->used_lrs)
                vgic_fold_lr_state(vcpu);
        vgic_prune_ap_list(vcpu);
}

/* Flush our emulation state into the GIC hardware before entering the guest. */
void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
{
        WARN_ON(vgic_v4_flush_hwstate(vcpu));

        /*
         * If there are no virtual interrupts active or pending for this
         * VCPU, then there is no work to do and we can bail out without
         * taking any lock.  There is a potential race with someone injecting
         * interrupts to the VCPU, but it is a benign race as the VCPU will
         * either observe the new interrupt before or after doing this check,
         * and introducing additional synchronization mechanism doesn't change
         * this.
         */
        if (list_empty(&vcpu->arch.vgic_cpu.ap_list_head))
                return;

        DEBUG_SPINLOCK_BUG_ON(!irqs_disabled());

        spin_lock(&vcpu->arch.vgic_cpu.ap_list_lock);
        vgic_flush_lr_state(vcpu);
        spin_unlock(&vcpu->arch.vgic_cpu.ap_list_lock);
}

void kvm_vgic_load(struct kvm_vcpu *vcpu)
{
        if (unlikely(!vgic_initialized(vcpu->kvm)))
                return;

        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_load(vcpu);
        else
                vgic_v3_load(vcpu);
}

void kvm_vgic_put(struct kvm_vcpu *vcpu)
{
        if (unlikely(!vgic_initialized(vcpu->kvm)))
                return;

        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_put(vcpu);
        else
                vgic_v3_put(vcpu);
}

int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
{
        struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
        struct vgic_irq *irq;
        bool pending = false;
        unsigned long flags;

        if (!vcpu->kvm->arch.vgic.enabled)
                return false;

        if (vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last)
                return true;

        spin_lock_irqsave(&vgic_cpu->ap_list_lock, flags);

        list_for_each_entry(irq, &vgic_cpu->ap_list_head, ap_list) {
                spin_lock(&irq->irq_lock);
                pending = irq_is_pending(irq) && irq->enabled;
                spin_unlock(&irq->irq_lock);

                if (pending)
                        break;
        }

        spin_unlock_irqrestore(&vgic_cpu->ap_list_lock, flags);

        return pending;
}

void vgic_kick_vcpus(struct kvm *kvm)
{
        struct kvm_vcpu *vcpu;
        int c;

        /*
         * We've injected an interrupt, time to find out who deserves
         * a good kick...
         */
        kvm_for_each_vcpu(c, vcpu, kvm) {
                if (kvm_vgic_vcpu_pending_irq(vcpu)) {
                        kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
                        kvm_vcpu_kick(vcpu);
                }
        }
}

bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int vintid)
{
        struct vgic_irq *irq;
        bool map_is_active;
        unsigned long flags;

        if (!vgic_initialized(vcpu->kvm))
                return false;

        irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
        spin_lock_irqsave(&irq->irq_lock, flags);
        map_is_active = irq->hw && irq->active;
        spin_unlock_irqrestore(&irq->irq_lock, flags);
        vgic_put_irq(vcpu->kvm, irq);

        return map_is_active;
}