/*
 * VGIC MMIO handling functions
 *
 * 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.
 */

#include <linux/bitops.h>
#include <linux/bsearch.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <kvm/iodev.h>
#include <kvm/arm_arch_timer.h>
#include <kvm/arm_vgic.h>

#include "vgic.h"
#include "vgic-mmio.h"

unsigned long vgic_mmio_read_raz(struct kvm_vcpu *vcpu,
                                 gpa_t addr, unsigned int len)
{
        return 0;
}

unsigned long vgic_mmio_read_rao(struct kvm_vcpu *vcpu,
                                 gpa_t addr, unsigned int len)
{
        return -1UL;
}

void vgic_mmio_write_wi(struct kvm_vcpu *vcpu, gpa_t addr,
                        unsigned int len, unsigned long val)
{
        /* Ignore */
}

/*
 * Read accesses to both GICD_ICENABLER and GICD_ISENABLER return the value
 * of the enabled bit, so there is only one function for both here.
 */
unsigned long vgic_mmio_read_enable(struct kvm_vcpu *vcpu,
                                    gpa_t addr, unsigned int len)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        u32 value = 0;
        int i;

        /* Loop over all IRQs affected by this read */
        for (i = 0; i < len * 8; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                if (irq->enabled)
                        value |= (1U << i);

                vgic_put_irq(vcpu->kvm, irq);
        }

        return value;
}

void vgic_mmio_write_senable(struct kvm_vcpu *vcpu,
                             gpa_t addr, unsigned int len,
                             unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;
        unsigned long flags;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                spin_lock_irqsave(&irq->irq_lock, flags);
                irq->enabled = true;
                vgic_queue_irq_unlock(vcpu->kvm, irq, flags);

                vgic_put_irq(vcpu->kvm, irq);
        }
}

void vgic_mmio_write_cenable(struct kvm_vcpu *vcpu,
                             gpa_t addr, unsigned int len,
                             unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;
        unsigned long flags;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                spin_lock_irqsave(&irq->irq_lock, flags);

                irq->enabled = false;

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

unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
                                     gpa_t addr, unsigned int len)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        u32 value = 0;
        int i;

        /* Loop over all IRQs affected by this read */
        for (i = 0; i < len * 8; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
                unsigned long flags;

                spin_lock_irqsave(&irq->irq_lock, flags);
                if (irq_is_pending(irq))
                        value |= (1U << i);
                spin_unlock_irqrestore(&irq->irq_lock, flags);

                vgic_put_irq(vcpu->kvm, irq);
        }

        return value;
}

/*
 * This function will return the VCPU that performed the MMIO access and
 * trapped from within the VM, and will return NULL if this is a userspace
 * access.
 *
 * We can disable preemption locally around accessing the per-CPU variable,
 * and use the resolved vcpu pointer after enabling preemption again, because
 * even if the current thread is migrated to another CPU, reading the per-CPU
 * value later will give us the same value as we update the per-CPU variable
 * in the preempt notifier handlers.
 */
static struct kvm_vcpu *vgic_get_mmio_requester_vcpu(void)
{
        struct kvm_vcpu *vcpu;

        preempt_disable();
        vcpu = kvm_arm_get_running_vcpu();
        preempt_enable();
        return vcpu;
}

/* Must be called with irq->irq_lock held */
static void vgic_hw_irq_spending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
                                 bool is_uaccess)
{
        if (is_uaccess)
                return;

        irq->pending_latch = true;
        vgic_irq_set_phys_active(irq, true);
}

void vgic_mmio_write_spending(struct kvm_vcpu *vcpu,
                              gpa_t addr, unsigned int len,
                              unsigned long val)
{
        bool is_uaccess = !vgic_get_mmio_requester_vcpu();
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;
        unsigned long flags;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                spin_lock_irqsave(&irq->irq_lock, flags);
                if (irq->hw)
                        vgic_hw_irq_spending(vcpu, irq, is_uaccess);
                else
                        irq->pending_latch = true;
                vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
                vgic_put_irq(vcpu->kvm, irq);
        }
}

/* Must be called with irq->irq_lock held */
static void vgic_hw_irq_cpending(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
                                 bool is_uaccess)
{
        if (is_uaccess)
                return;

        irq->pending_latch = false;

        /*
         * We don't want the guest to effectively mask the physical
         * interrupt by doing a write to SPENDR followed by a write to
         * CPENDR for HW interrupts, so we clear the active state on
         * the physical side if the virtual interrupt is not active.
         * This may lead to taking an additional interrupt on the
         * host, but that should not be a problem as the worst that
         * can happen is an additional vgic injection.  We also clear
         * the pending state to maintain proper semantics for edge HW
         * interrupts.
         */
        vgic_irq_set_phys_pending(irq, false);
        if (!irq->active)
                vgic_irq_set_phys_active(irq, false);
}

void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
                              gpa_t addr, unsigned int len,
                              unsigned long val)
{
        bool is_uaccess = !vgic_get_mmio_requester_vcpu();
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;
        unsigned long flags;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                spin_lock_irqsave(&irq->irq_lock, flags);

                if (irq->hw)
                        vgic_hw_irq_cpending(vcpu, irq, is_uaccess);
                else
                        irq->pending_latch = false;

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

unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
                                    gpa_t addr, unsigned int len)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        u32 value = 0;
        int i;

        /* Loop over all IRQs affected by this read */
        for (i = 0; i < len * 8; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                if (irq->active)
                        value |= (1U << i);

                vgic_put_irq(vcpu->kvm, irq);
        }

        return value;
}

/* Must be called with irq->irq_lock held */
static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
                                      bool active, bool is_uaccess)
{
        if (is_uaccess)
                return;

        irq->active = active;
        vgic_irq_set_phys_active(irq, active);
}

static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
                                    bool active)
{
        unsigned long flags;
        struct kvm_vcpu *requester_vcpu = vgic_get_mmio_requester_vcpu();

        spin_lock_irqsave(&irq->irq_lock, flags);

        /*
         * If this virtual IRQ was written into a list register, we
         * have to make sure the CPU that runs the VCPU thread has
         * synced back the LR state to the struct vgic_irq.
         *
         * As long as the conditions below are true, we know the VCPU thread
         * may be on its way back from the guest (we kicked the VCPU thread in
         * vgic_change_active_prepare)  and still has to sync back this IRQ,
         * so we release and re-acquire the spin_lock to let the other thread
         * sync back the IRQ.
         *
         * When accessing VGIC state from user space, requester_vcpu is
         * NULL, which is fine, because we guarantee that no VCPUs are running
         * when accessing VGIC state from user space so irq->vcpu->cpu is
         * always -1.
         */
        while (irq->vcpu && /* IRQ may have state in an LR somewhere */
               irq->vcpu != requester_vcpu && /* Current thread is not the VCPU thread */
               irq->vcpu->cpu != -1) /* VCPU thread is running */
                cond_resched_lock(&irq->irq_lock);

        if (irq->hw)
                vgic_hw_irq_change_active(vcpu, irq, active, !requester_vcpu);
        else
                irq->active = active;

        if (irq->active)
                vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
        else
                spin_unlock_irqrestore(&irq->irq_lock, flags);
}

/*
 * If we are fiddling with an IRQ's active state, we have to make sure the IRQ
 * is not queued on some running VCPU's LRs, because then the change to the
 * active state can be overwritten when the VCPU's state is synced coming back
 * from the guest.
 *
 * For shared interrupts, we have to stop all the VCPUs because interrupts can
 * be migrated while we don't hold the IRQ locks and we don't want to be
 * chasing moving targets.
 *
 * For private interrupts we don't have to do anything because userspace
 * accesses to the VGIC state already require all VCPUs to be stopped, and
 * only the VCPU itself can modify its private interrupts active state, which
 * guarantees that the VCPU is not running.
 */
static void vgic_change_active_prepare(struct kvm_vcpu *vcpu, u32 intid)
{
        if (intid > VGIC_NR_PRIVATE_IRQS)
                kvm_arm_halt_guest(vcpu->kvm);
}

/* See vgic_change_active_prepare */
static void vgic_change_active_finish(struct kvm_vcpu *vcpu, u32 intid)
{
        if (intid > VGIC_NR_PRIVATE_IRQS)
                kvm_arm_resume_guest(vcpu->kvm);
}

static void __vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
                                      gpa_t addr, unsigned int len,
                                      unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
                vgic_mmio_change_active(vcpu, irq, false);
                vgic_put_irq(vcpu->kvm, irq);
        }
}

void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
                             gpa_t addr, unsigned int len,
                             unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);

        mutex_lock(&vcpu->kvm->lock);
        vgic_change_active_prepare(vcpu, intid);

        __vgic_mmio_write_cactive(vcpu, addr, len, val);

        vgic_change_active_finish(vcpu, intid);
        mutex_unlock(&vcpu->kvm->lock);
}

void vgic_mmio_uaccess_write_cactive(struct kvm_vcpu *vcpu,
                                     gpa_t addr, unsigned int len,
                                     unsigned long val)
{
        __vgic_mmio_write_cactive(vcpu, addr, len, val);
}

static void __vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
                                      gpa_t addr, unsigned int len,
                                      unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
        int i;

        for_each_set_bit(i, &val, len * 8) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
                vgic_mmio_change_active(vcpu, irq, true);
                vgic_put_irq(vcpu->kvm, irq);
        }
}

void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
                             gpa_t addr, unsigned int len,
                             unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 1);

        mutex_lock(&vcpu->kvm->lock);
        vgic_change_active_prepare(vcpu, intid);

        __vgic_mmio_write_sactive(vcpu, addr, len, val);

        vgic_change_active_finish(vcpu, intid);
        mutex_unlock(&vcpu->kvm->lock);
}

void vgic_mmio_uaccess_write_sactive(struct kvm_vcpu *vcpu,
                                     gpa_t addr, unsigned int len,
                                     unsigned long val)
{
        __vgic_mmio_write_sactive(vcpu, addr, len, val);
}

unsigned long vgic_mmio_read_priority(struct kvm_vcpu *vcpu,
                                      gpa_t addr, unsigned int len)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
        int i;
        u64 val = 0;

        for (i = 0; i < len; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                val |= (u64)irq->priority << (i * 8);

                vgic_put_irq(vcpu->kvm, irq);
        }

        return val;
}

/*
 * We currently don't handle changing the priority of an interrupt that
 * is already pending on a VCPU. If there is a need for this, we would
 * need to make this VCPU exit and re-evaluate the priorities, potentially
 * leading to this interrupt getting presented now to the guest (if it has
 * been masked by the priority mask before).
 */
void vgic_mmio_write_priority(struct kvm_vcpu *vcpu,
                              gpa_t addr, unsigned int len,
                              unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 8);
        int i;
        unsigned long flags;

        for (i = 0; i < len; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                spin_lock_irqsave(&irq->irq_lock, flags);
                /* Narrow the priority range to what we actually support */
                irq->priority = (val >> (i * 8)) & GENMASK(7, 8 - VGIC_PRI_BITS);
                spin_unlock_irqrestore(&irq->irq_lock, flags);

                vgic_put_irq(vcpu->kvm, irq);
        }
}

unsigned long vgic_mmio_read_config(struct kvm_vcpu *vcpu,
                                    gpa_t addr, unsigned int len)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 2);
        u32 value = 0;
        int i;

        for (i = 0; i < len * 4; i++) {
                struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                if (irq->config == VGIC_CONFIG_EDGE)
                        value |= (2U << (i * 2));

                vgic_put_irq(vcpu->kvm, irq);
        }

        return value;
}

void vgic_mmio_write_config(struct kvm_vcpu *vcpu,
                            gpa_t addr, unsigned int len,
                            unsigned long val)
{
        u32 intid = VGIC_ADDR_TO_INTID(addr, 2);
        int i;
        unsigned long flags;

        for (i = 0; i < len * 4; i++) {
                struct vgic_irq *irq;

                /*
                 * The configuration cannot be changed for SGIs in general,
                 * for PPIs this is IMPLEMENTATION DEFINED. The arch timer
                 * code relies on PPIs being level triggered, so we also
                 * make them read-only here.
                 */
                if (intid + i < VGIC_NR_PRIVATE_IRQS)
                        continue;

                irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
                spin_lock_irqsave(&irq->irq_lock, flags);

                if (test_bit(i * 2 + 1, &val))
                        irq->config = VGIC_CONFIG_EDGE;
                else
                        irq->config = VGIC_CONFIG_LEVEL;

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

u64 vgic_read_irq_line_level_info(struct kvm_vcpu *vcpu, u32 intid)
{
        int i;
        u64 val = 0;
        int nr_irqs = vcpu->kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;

        for (i = 0; i < 32; i++) {
                struct vgic_irq *irq;

                if ((intid + i) < VGIC_NR_SGIS || (intid + i) >= nr_irqs)
                        continue;

                irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
                if (irq->config == VGIC_CONFIG_LEVEL && irq->line_level)
                        val |= (1U << i);

                vgic_put_irq(vcpu->kvm, irq);
        }

        return val;
}

void vgic_write_irq_line_level_info(struct kvm_vcpu *vcpu, u32 intid,
                                    const u64 val)
{
        int i;
        int nr_irqs = vcpu->kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;
        unsigned long flags;

        for (i = 0; i < 32; i++) {
                struct vgic_irq *irq;
                bool new_level;

                if ((intid + i) < VGIC_NR_SGIS || (intid + i) >= nr_irqs)
                        continue;

                irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);

                /*
                 * Line level is set irrespective of irq type
                 * (level or edge) to avoid dependency that VM should
                 * restore irq config before line level.
                 */
                new_level = !!(val & (1U << i));
                spin_lock_irqsave(&irq->irq_lock, flags);
                irq->line_level = new_level;
                if (new_level)
                        vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
                else
                        spin_unlock_irqrestore(&irq->irq_lock, flags);

                vgic_put_irq(vcpu->kvm, irq);
        }
}

static int match_region(const void *key, const void *elt)
{
        const unsigned int offset = (unsigned long)key;
        const struct vgic_register_region *region = elt;

        if (offset < region->reg_offset)
                return -1;

        if (offset >= region->reg_offset + region->len)
                return 1;

        return 0;
}

const struct vgic_register_region *
vgic_find_mmio_region(const struct vgic_register_region *regions,
                      int nr_regions, unsigned int offset)
{
        return bsearch((void *)(uintptr_t)offset, regions, nr_regions,
                       sizeof(regions[0]), match_region);
}

void vgic_set_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcr)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_set_vmcr(vcpu, vmcr);
        else
                vgic_v3_set_vmcr(vcpu, vmcr);
}

void vgic_get_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcr)
{
        if (kvm_vgic_global_state.type == VGIC_V2)
                vgic_v2_get_vmcr(vcpu, vmcr);
        else
                vgic_v3_get_vmcr(vcpu, vmcr);
}

/*
 * kvm_mmio_read_buf() returns a value in a format where it can be converted
 * to a byte array and be directly observed as the guest wanted it to appear
 * in memory if it had done the store itself, which is LE for the GIC, as the
 * guest knows the GIC is always LE.
 *
 * We convert this value to the CPUs native format to deal with it as a data
 * value.
 */
unsigned long vgic_data_mmio_bus_to_host(const void *val, unsigned int len)
{
        unsigned long data = kvm_mmio_read_buf(val, len);

        switch (len) {
        case 1:
                return data;
        case 2:
                return le16_to_cpu(data);
        case 4:
                return le32_to_cpu(data);
        default:
                return le64_to_cpu(data);
        }
}

/*
 * kvm_mmio_write_buf() expects a value in a format such that if converted to
 * a byte array it is observed as the guest would see it if it could perform
 * the load directly.  Since the GIC is LE, and the guest knows this, the
 * guest expects a value in little endian format.
 *
 * We convert the data value from the CPUs native format to LE so that the
 * value is returned in the proper format.
 */
void vgic_data_host_to_mmio_bus(void *buf, unsigned int len,
                                unsigned long data)
{
        switch (len) {
        case 1:
                break;
        case 2:
                data = cpu_to_le16(data);
                break;
        case 4:
                data = cpu_to_le32(data);
                break;
        default:
                data = cpu_to_le64(data);
        }

        kvm_mmio_write_buf(buf, len, data);
}

static
struct vgic_io_device *kvm_to_vgic_iodev(const struct kvm_io_device *dev)
{
        return container_of(dev, struct vgic_io_device, dev);
}

static bool check_region(const struct kvm *kvm,
                         const struct vgic_register_region *region,
                         gpa_t addr, int len)
{
        int flags, nr_irqs = kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;

        switch (len) {
        case sizeof(u8):
                flags = VGIC_ACCESS_8bit;
                break;
        case sizeof(u32):
                flags = VGIC_ACCESS_32bit;
                break;
        case sizeof(u64):
                flags = VGIC_ACCESS_64bit;
                break;
        default:
                return false;
        }

        if ((region->access_flags & flags) && IS_ALIGNED(addr, len)) {
                if (!region->bits_per_irq)
                        return true;

                /* Do we access a non-allocated IRQ? */
                return VGIC_ADDR_TO_INTID(addr, region->bits_per_irq) < nr_irqs;
        }

        return false;
}

const struct vgic_register_region *
vgic_get_mmio_region(struct kvm_vcpu *vcpu, struct vgic_io_device *iodev,
                     gpa_t addr, int len)
{
        const struct vgic_register_region *region;

        region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
                                       addr - iodev->base_addr);
        if (!region || !check_region(vcpu->kvm, region, addr, len))
                return NULL;

        return region;
}

static int vgic_uaccess_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
                             gpa_t addr, u32 *val)
{
        struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
        const struct vgic_register_region *region;
        struct kvm_vcpu *r_vcpu;

        region = vgic_get_mmio_region(vcpu, iodev, addr, sizeof(u32));
        if (!region) {
                *val = 0;
                return 0;
        }

        r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
        if (region->uaccess_read)
                *val = region->uaccess_read(r_vcpu, addr, sizeof(u32));
        else
                *val = region->read(r_vcpu, addr, sizeof(u32));

        return 0;
}

static int vgic_uaccess_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
                              gpa_t addr, const u32 *val)
{
        struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
        const struct vgic_register_region *region;
        struct kvm_vcpu *r_vcpu;

        region = vgic_get_mmio_region(vcpu, iodev, addr, sizeof(u32));
        if (!region)
                return 0;

        r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
        if (region->uaccess_write)
                region->uaccess_write(r_vcpu, addr, sizeof(u32), *val);
        else
                region->write(r_vcpu, addr, sizeof(u32), *val);

        return 0;
}

/*
 * Userland access to VGIC registers.
 */
int vgic_uaccess(struct kvm_vcpu *vcpu, struct vgic_io_device *dev,
                 bool is_write, int offset, u32 *val)
{
        if (is_write)
                return vgic_uaccess_write(vcpu, &dev->dev, offset, val);
        else
                return vgic_uaccess_read(vcpu, &dev->dev, offset, val);
}

static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
                              gpa_t addr, int len, void *val)
{
        struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
        const struct vgic_register_region *region;
        unsigned long data = 0;

        region = vgic_get_mmio_region(vcpu, iodev, addr, len);
        if (!region) {
                memset(val, 0, len);
                return 0;
        }

        switch (iodev->iodev_type) {
        case IODEV_CPUIF:
                data = region->read(vcpu, addr, len);
                break;
        case IODEV_DIST:
                data = region->read(vcpu, addr, len);
                break;
        case IODEV_REDIST:
                data = region->read(iodev->redist_vcpu, addr, len);
                break;
        case IODEV_ITS:
                data = region->its_read(vcpu->kvm, iodev->its, addr, len);
                break;
        }

        vgic_data_host_to_mmio_bus(val, len, data);
        return 0;
}

static int dispatch_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
                               gpa_t addr, int len, const void *val)
{
        struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
        const struct vgic_register_region *region;
        unsigned long data = vgic_data_mmio_bus_to_host(val, len);

        region = vgic_get_mmio_region(vcpu, iodev, addr, len);
        if (!region)
                return 0;

        switch (iodev->iodev_type) {
        case IODEV_CPUIF:
                region->write(vcpu, addr, len, data);
                break;
        case IODEV_DIST:
                region->write(vcpu, addr, len, data);
                break;
        case IODEV_REDIST:
                region->write(iodev->redist_vcpu, addr, len, data);
                break;
        case IODEV_ITS:
                region->its_write(vcpu->kvm, iodev->its, addr, len, data);
                break;
        }

        return 0;
}

struct kvm_io_device_ops kvm_io_gic_ops = {
        .read = dispatch_mmio_read,
        .write = dispatch_mmio_write,
};

int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
                             enum vgic_type type)
{
        struct vgic_io_device *io_device = &kvm->arch.vgic.dist_iodev;
        int ret = 0;
        unsigned int len;

        switch (type) {
        case VGIC_V2:
                len = vgic_v2_init_dist_iodev(io_device);
                break;
        case VGIC_V3:
                len = vgic_v3_init_dist_iodev(io_device);
                break;
        default:
                BUG_ON(1);
        }

        io_device->base_addr = dist_base_address;
        io_device->iodev_type = IODEV_DIST;
        io_device->redist_vcpu = NULL;

        mutex_lock(&kvm->slots_lock);
        ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, dist_base_address,
                                      len, &io_device->dev);
        mutex_unlock(&kvm->slots_lock);

        return ret;
}