qemu/hw/vfio/platform.c

/*
 * vfio based device assignment support - platform devices
 *
 * Copyright Linaro Limited, 2014
 *
 * Authors:
 *  Kim Phillips <kim.phillips@linaro.org>
 *  Eric Auger <eric.auger@linaro.org>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 * Based on vfio based PCI device assignment support:
 *  Copyright Red Hat, Inc. 2012
 */

#include "qemu/osdep.h"
#include "qapi/error.h"
#include <sys/ioctl.h>
#include <linux/vfio.h>

#include "hw/vfio/vfio-platform.h"
#include "qemu/error-report.h"
#include "qemu/range.h"
#include "sysemu/sysemu.h"
#include "exec/memory.h"
#include "exec/address-spaces.h"
#include "qemu/queue.h"
#include "hw/sysbus.h"
#include "trace.h"
#include "hw/platform-bus.h"
#include "sysemu/kvm.h"

/*
 * Functions used whatever the injection method
 */

static inline bool vfio_irq_is_automasked(VFIOINTp *intp)
{
    return intp->flags & VFIO_IRQ_INFO_AUTOMASKED;
}

/**
 * vfio_init_intp - allocate, initialize the IRQ struct pointer
 * and add it into the list of IRQs
 * @vbasedev: the VFIO device handle
 * @info: irq info struct retrieved from VFIO driver
 * @errp: error object
 */
static VFIOINTp *vfio_init_intp(VFIODevice *vbasedev,
                                struct vfio_irq_info info, Error **errp)
{
    int ret;
    VFIOPlatformDevice *vdev =
        container_of(vbasedev, VFIOPlatformDevice, vbasedev);
    SysBusDevice *sbdev = SYS_BUS_DEVICE(vdev);
    VFIOINTp *intp;

    intp = g_malloc0(sizeof(*intp));
    intp->vdev = vdev;
    intp->pin = info.index;
    intp->flags = info.flags;
    intp->state = VFIO_IRQ_INACTIVE;
    intp->kvm_accel = false;

    sysbus_init_irq(sbdev, &intp->qemuirq);

    /* Get an eventfd for trigger */
    intp->interrupt = g_malloc0(sizeof(EventNotifier));
    ret = event_notifier_init(intp->interrupt, 0);
    if (ret) {
        g_free(intp->interrupt);
        g_free(intp);
        error_setg_errno(errp, -ret,
                         "failed to initialize trigger eventd notifier");
        return NULL;
    }
    if (vfio_irq_is_automasked(intp)) {
        /* Get an eventfd for resample/unmask */
        intp->unmask = g_malloc0(sizeof(EventNotifier));
        ret = event_notifier_init(intp->unmask, 0);
        if (ret) {
            g_free(intp->interrupt);
            g_free(intp->unmask);
            g_free(intp);
            error_setg_errno(errp, -ret,
                             "failed to initialize resample eventd notifier");
            return NULL;
        }
    }

    QLIST_INSERT_HEAD(&vdev->intp_list, intp, next);
    return intp;
}

/**
 * vfio_set_trigger_eventfd - set VFIO eventfd handling
 *
 * @intp: IRQ struct handle
 * @handler: handler to be called on eventfd signaling
 *
 * Setup VFIO signaling and attach an optional user-side handler
 * to the eventfd
 */
static int vfio_set_trigger_eventfd(VFIOINTp *intp,
                                    eventfd_user_side_handler_t handler)
{
    VFIODevice *vbasedev = &intp->vdev->vbasedev;
    struct vfio_irq_set *irq_set;
    int argsz, ret;
    int32_t *pfd;

    argsz = sizeof(*irq_set) + sizeof(*pfd);
    irq_set = g_malloc0(argsz);
    irq_set->argsz = argsz;
    irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_TRIGGER;
    irq_set->index = intp->pin;
    irq_set->start = 0;
    irq_set->count = 1;
    pfd = (int32_t *)&irq_set->data;
    *pfd = event_notifier_get_fd(intp->interrupt);
    qemu_set_fd_handler(*pfd, (IOHandler *)handler, NULL, intp);
    ret = ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
    if (ret < 0) {
        error_report("vfio: Failed to set trigger eventfd: %m");
        qemu_set_fd_handler(*pfd, NULL, NULL, NULL);
    }
    g_free(irq_set);
    return ret;
}

/*
 * Functions only used when eventfds are handled on user-side
 * ie. without irqfd
 */

/**
 * vfio_mmap_set_enabled - enable/disable the fast path mode
 * @vdev: the VFIO platform device
 * @enabled: the target mmap state
 *
 * enabled = true ~ fast path = MMIO region is mmaped (no KVM TRAP);
 * enabled = false ~ slow path = MMIO region is trapped and region callbacks
 * are called; slow path enables to trap the device IRQ status register reset
*/

static void vfio_mmap_set_enabled(VFIOPlatformDevice *vdev, bool enabled)
{
    int i;

    for (i = 0; i < vdev->vbasedev.num_regions; i++) {
        vfio_region_mmaps_set_enabled(vdev->regions[i], enabled);
    }
}

/**
 * vfio_intp_mmap_enable - timer function, restores the fast path
 * if there is no more active IRQ
 * @opaque: actually points to the VFIO platform device
 *
 * Called on mmap timer timout, this function checks whether the
 * IRQ is still active and if not, restores the fast path.
 * by construction a single eventfd is handled at a time.
 * if the IRQ is still active, the timer is re-programmed.
 */
static void vfio_intp_mmap_enable(void *opaque)
{
    VFIOINTp *tmp;
    VFIOPlatformDevice *vdev = (VFIOPlatformDevice *)opaque;

    qemu_mutex_lock(&vdev->intp_mutex);
    QLIST_FOREACH(tmp, &vdev->intp_list, next) {
        if (tmp->state == VFIO_IRQ_ACTIVE) {
            trace_vfio_platform_intp_mmap_enable(tmp->pin);
            /* re-program the timer to check active status later */
            timer_mod(vdev->mmap_timer,
                      qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
                          vdev->mmap_timeout);
            qemu_mutex_unlock(&vdev->intp_mutex);
            return;
        }
    }
    vfio_mmap_set_enabled(vdev, true);
    qemu_mutex_unlock(&vdev->intp_mutex);
}

/**
 * vfio_intp_inject_pending_lockheld - Injects a pending IRQ
 * @opaque: opaque pointer, in practice the VFIOINTp handle
 *
 * The function is called on a previous IRQ completion, from
 * vfio_platform_eoi, while the intp_mutex is locked.
 * Also in such situation, the slow path already is set and
 * the mmap timer was already programmed.
 */
static void vfio_intp_inject_pending_lockheld(VFIOINTp *intp)
{
    trace_vfio_platform_intp_inject_pending_lockheld(intp->pin,
                              event_notifier_get_fd(intp->interrupt));

    intp->state = VFIO_IRQ_ACTIVE;

    /* trigger the virtual IRQ */
    qemu_set_irq(intp->qemuirq, 1);
}

/**
 * vfio_intp_interrupt - The user-side eventfd handler
 * @opaque: opaque pointer which in practice is the VFIOINTp handle
 *
 * the function is entered in event handler context:
 * the vIRQ is injected into the guest if there is no other active
 * or pending IRQ.
 */
static void vfio_intp_interrupt(VFIOINTp *intp)
{
    int ret;
    VFIOINTp *tmp;
    VFIOPlatformDevice *vdev = intp->vdev;
    bool delay_handling = false;

    qemu_mutex_lock(&vdev->intp_mutex);
    if (intp->state == VFIO_IRQ_INACTIVE) {
        QLIST_FOREACH(tmp, &vdev->intp_list, next) {
            if (tmp->state == VFIO_IRQ_ACTIVE ||
                tmp->state == VFIO_IRQ_PENDING) {
                delay_handling = true;
                break;
            }
        }
    }
    if (delay_handling) {
        /*
         * the new IRQ gets a pending status and is pushed in
         * the pending queue
         */
        intp->state = VFIO_IRQ_PENDING;
        trace_vfio_intp_interrupt_set_pending(intp->pin);
        QSIMPLEQ_INSERT_TAIL(&vdev->pending_intp_queue,
                             intp, pqnext);
        ret = event_notifier_test_and_clear(intp->interrupt);
        qemu_mutex_unlock(&vdev->intp_mutex);
        return;
    }

    trace_vfio_platform_intp_interrupt(intp->pin,
                              event_notifier_get_fd(intp->interrupt));

    ret = event_notifier_test_and_clear(intp->interrupt);
    if (!ret) {
        error_report("Error when clearing fd=%d (ret = %d)",
                     event_notifier_get_fd(intp->interrupt), ret);
    }

    intp->state = VFIO_IRQ_ACTIVE;

    /* sets slow path */
    vfio_mmap_set_enabled(vdev, false);

    /* trigger the virtual IRQ */
    qemu_set_irq(intp->qemuirq, 1);

    /*
     * Schedule the mmap timer which will restore fastpath when no IRQ
     * is active anymore
     */
    if (vdev->mmap_timeout) {
        timer_mod(vdev->mmap_timer,
                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
                      vdev->mmap_timeout);
    }
    qemu_mutex_unlock(&vdev->intp_mutex);
}

/**
 * vfio_platform_eoi - IRQ completion routine
 * @vbasedev: the VFIO device handle
 *
 * De-asserts the active virtual IRQ and unmasks the physical IRQ
 * (effective for level sensitive IRQ auto-masked by the  VFIO driver).
 * Then it handles next pending IRQ if any.
 * eoi function is called on the first access to any MMIO region
 * after an IRQ was triggered, trapped since slow path was set.
 * It is assumed this access corresponds to the IRQ status
 * register reset. With such a mechanism, a single IRQ can be
 * handled at a time since there is no way to know which IRQ
 * was completed by the guest (we would need additional details
 * about the IRQ status register mask).
 */
static void vfio_platform_eoi(VFIODevice *vbasedev)
{
    VFIOINTp *intp;
    VFIOPlatformDevice *vdev =
        container_of(vbasedev, VFIOPlatformDevice, vbasedev);

    qemu_mutex_lock(&vdev->intp_mutex);
    QLIST_FOREACH(intp, &vdev->intp_list, next) {
        if (intp->state == VFIO_IRQ_ACTIVE) {
            trace_vfio_platform_eoi(intp->pin,
                                event_notifier_get_fd(intp->interrupt));
            intp->state = VFIO_IRQ_INACTIVE;

            /* deassert the virtual IRQ */
            qemu_set_irq(intp->qemuirq, 0);

            if (vfio_irq_is_automasked(intp)) {
                /* unmasks the physical level-sensitive IRQ */
                vfio_unmask_single_irqindex(vbasedev, intp->pin);
            }

            /* a single IRQ can be active at a time */
            break;
        }
    }
    /* in case there are pending IRQs, handle the first one */
    if (!QSIMPLEQ_EMPTY(&vdev->pending_intp_queue)) {
        intp = QSIMPLEQ_FIRST(&vdev->pending_intp_queue);
        vfio_intp_inject_pending_lockheld(intp);
        QSIMPLEQ_REMOVE_HEAD(&vdev->pending_intp_queue, pqnext);
    }
    qemu_mutex_unlock(&vdev->intp_mutex);
}

/**
 * vfio_start_eventfd_injection - starts the virtual IRQ injection using
 * user-side handled eventfds
 * @sbdev: the sysbus device handle
 * @irq: the qemu irq handle
 */

static void vfio_start_eventfd_injection(SysBusDevice *sbdev, qemu_irq irq)
{
    int ret;
    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(sbdev);
    VFIOINTp *intp;

    QLIST_FOREACH(intp, &vdev->intp_list, next) {
        if (intp->qemuirq == irq) {
            break;
        }
    }
    assert(intp);

    ret = vfio_set_trigger_eventfd(intp, vfio_intp_interrupt);
    if (ret) {
        error_report("vfio: failed to start eventfd signaling for IRQ %d: %m",
                     intp->pin);
        abort();
    }
}

/*
 * Functions used for irqfd
 */

/**
 * vfio_set_resample_eventfd - sets the resamplefd for an IRQ
 * @intp: the IRQ struct handle
 * programs the VFIO driver to unmask this IRQ when the
 * intp->unmask eventfd is triggered
 */
static int vfio_set_resample_eventfd(VFIOINTp *intp)
{
    VFIODevice *vbasedev = &intp->vdev->vbasedev;
    struct vfio_irq_set *irq_set;
    int argsz, ret;
    int32_t *pfd;

    argsz = sizeof(*irq_set) + sizeof(*pfd);
    irq_set = g_malloc0(argsz);
    irq_set->argsz = argsz;
    irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD | VFIO_IRQ_SET_ACTION_UNMASK;
    irq_set->index = intp->pin;
    irq_set->start = 0;
    irq_set->count = 1;
    pfd = (int32_t *)&irq_set->data;
    *pfd = event_notifier_get_fd(intp->unmask);
    qemu_set_fd_handler(*pfd, NULL, NULL, NULL);
    ret = ioctl(vbasedev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
    g_free(irq_set);
    if (ret < 0) {
        error_report("vfio: Failed to set resample eventfd: %m");
    }
    return ret;
}

/**
 * vfio_start_irqfd_injection - starts the virtual IRQ injection using
 * irqfd
 *
 * @sbdev: the sysbus device handle
 * @irq: the qemu irq handle
 *
 * In case the irqfd setup fails, we fallback to userspace handled eventfd
 */
static void vfio_start_irqfd_injection(SysBusDevice *sbdev, qemu_irq irq)
{
    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(sbdev);
    VFIOINTp *intp;

    if (!kvm_irqfds_enabled() || !kvm_resamplefds_enabled() ||
        !vdev->irqfd_allowed) {
        goto fail_irqfd;
    }

    QLIST_FOREACH(intp, &vdev->intp_list, next) {
        if (intp->qemuirq == irq) {
            break;
        }
    }
    assert(intp);

    if (kvm_irqchip_add_irqfd_notifier(kvm_state, intp->interrupt,
                                   intp->unmask, irq) < 0) {
        goto fail_irqfd;
    }

    if (vfio_set_trigger_eventfd(intp, NULL) < 0) {
        goto fail_vfio;
    }
    if (vfio_irq_is_automasked(intp)) {
        if (vfio_set_resample_eventfd(intp) < 0) {
            goto fail_vfio;
        }
        trace_vfio_platform_start_level_irqfd_injection(intp->pin,
                                    event_notifier_get_fd(intp->interrupt),
                                    event_notifier_get_fd(intp->unmask));
    } else {
        trace_vfio_platform_start_edge_irqfd_injection(intp->pin,
                                    event_notifier_get_fd(intp->interrupt));
    }

    intp->kvm_accel = true;

    return;
fail_vfio:
    kvm_irqchip_remove_irqfd_notifier(kvm_state, intp->interrupt, irq);
    error_report("vfio: failed to start eventfd signaling for IRQ %d: %m",
                 intp->pin);
    abort();
fail_irqfd:
    vfio_start_eventfd_injection(sbdev, irq);
    return;
}

/* VFIO skeleton */

static void vfio_platform_compute_needs_reset(VFIODevice *vbasedev)
{
    vbasedev->needs_reset = true;
}

/* not implemented yet */
static int vfio_platform_hot_reset_multi(VFIODevice *vbasedev)
{
    return -1;
}

/**
 * vfio_populate_device - Allocate and populate MMIO region
 * and IRQ structs according to driver returned information
 * @vbasedev: the VFIO device handle
 * @errp: error object
 *
 */
static int vfio_populate_device(VFIODevice *vbasedev, Error **errp)
{
    VFIOINTp *intp, *tmp;
    int i, ret = -1;
    VFIOPlatformDevice *vdev =
        container_of(vbasedev, VFIOPlatformDevice, vbasedev);

    if (!(vbasedev->flags & VFIO_DEVICE_FLAGS_PLATFORM)) {
        error_setg(errp, "this isn't a platform device");
        return ret;
    }

    vdev->regions = g_new0(VFIORegion *, vbasedev->num_regions);

    for (i = 0; i < vbasedev->num_regions; i++) {
        char *name = g_strdup_printf("VFIO %s region %d\n", vbasedev->name, i);

        vdev->regions[i] = g_new0(VFIORegion, 1);
        ret = vfio_region_setup(OBJECT(vdev), vbasedev,
                                vdev->regions[i], i, name);
        g_free(name);
        if (ret) {
            error_setg_errno(errp, -ret, "failed to get region %d info", i);
            goto reg_error;
        }
    }

    vdev->mmap_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
                                    vfio_intp_mmap_enable, vdev);

    QSIMPLEQ_INIT(&vdev->pending_intp_queue);

    for (i = 0; i < vbasedev->num_irqs; i++) {
        struct vfio_irq_info irq = { .argsz = sizeof(irq) };

        irq.index = i;
        ret = ioctl(vbasedev->fd, VFIO_DEVICE_GET_IRQ_INFO, &irq);
        if (ret) {
            error_setg_errno(errp, -ret, "failed to get device irq info");
            goto irq_err;
        } else {
            trace_vfio_platform_populate_interrupts(irq.index,
                                                    irq.count,
                                                    irq.flags);
            intp = vfio_init_intp(vbasedev, irq, errp);
            if (!intp) {
                ret = -1;
                goto irq_err;
            }
        }
    }
    return 0;
irq_err:
    timer_del(vdev->mmap_timer);
    QLIST_FOREACH_SAFE(intp, &vdev->intp_list, next, tmp) {
        QLIST_REMOVE(intp, next);
        g_free(intp);
    }
reg_error:
    for (i = 0; i < vbasedev->num_regions; i++) {
        if (vdev->regions[i]) {
            vfio_region_finalize(vdev->regions[i]);
        }
        g_free(vdev->regions[i]);
    }
    g_free(vdev->regions);
    return ret;
}

/* specialized functions for VFIO Platform devices */
static VFIODeviceOps vfio_platform_ops = {
    .vfio_compute_needs_reset = vfio_platform_compute_needs_reset,
    .vfio_hot_reset_multi = vfio_platform_hot_reset_multi,
    .vfio_eoi = vfio_platform_eoi,
};

/**
 * vfio_base_device_init - perform preliminary VFIO setup
 * @vbasedev: the VFIO device handle
 * @errp: error object
 *
 * Implement the VFIO command sequence that allows to discover
 * assigned device resources: group extraction, device
 * fd retrieval, resource query.
 * Precondition: the device name must be initialized
 */
static int vfio_base_device_init(VFIODevice *vbasedev, Error **errp)
{
    VFIOGroup *group;
    VFIODevice *vbasedev_iter;
    char *tmp, group_path[PATH_MAX], *group_name;
    ssize_t len;
    struct stat st;
    int groupid;
    int ret;

    /* @sysfsdev takes precedence over @host */
    if (vbasedev->sysfsdev) {
        g_free(vbasedev->name);
        vbasedev->name = g_path_get_basename(vbasedev->sysfsdev);
    } else {
        if (!vbasedev->name || strchr(vbasedev->name, '/')) {
            error_setg(errp, "wrong host device name");
            return -EINVAL;
        }

        vbasedev->sysfsdev = g_strdup_printf("/sys/bus/platform/devices/%s",
                                             vbasedev->name);
    }

    if (stat(vbasedev->sysfsdev, &st) < 0) {
        error_setg_errno(errp, errno,
                         "failed to get the sysfs host device file status");
        return -errno;
    }

    tmp = g_strdup_printf("%s/iommu_group", vbasedev->sysfsdev);
    len = readlink(tmp, group_path, sizeof(group_path));
    g_free(tmp);

    if (len < 0 || len >= sizeof(group_path)) {
        ret = len < 0 ? -errno : -ENAMETOOLONG;
        error_setg_errno(errp, -ret, "no iommu_group found");
        return ret;
    }

    group_path[len] = 0;

    group_name = basename(group_path);
    if (sscanf(group_name, "%d", &groupid) != 1) {
        error_setg_errno(errp, errno, "failed to read %s", group_path);
        return -errno;
    }

    trace_vfio_platform_base_device_init(vbasedev->name, groupid);

    group = vfio_get_group(groupid, &address_space_memory, errp);
    if (!group) {
        return -ENOENT;
    }

    QLIST_FOREACH(vbasedev_iter, &group->device_list, next) {
        if (strcmp(vbasedev_iter->name, vbasedev->name) == 0) {
            error_setg(errp, "device is already attached");
            vfio_put_group(group);
            return -EBUSY;
        }
    }
    ret = vfio_get_device(group, vbasedev->name, vbasedev, errp);
    if (ret) {
        vfio_put_group(group);
        return ret;
    }

    ret = vfio_populate_device(vbasedev, errp);
    if (ret) {
        vfio_put_group(group);
    }

    return ret;
}

/**
 * vfio_platform_realize  - the device realize function
 * @dev: device state pointer
 * @errp: error
 *
 * initialize the device, its memory regions and IRQ structures
 * IRQ are started separately
 */
static void vfio_platform_realize(DeviceState *dev, Error **errp)
{
    VFIOPlatformDevice *vdev = VFIO_PLATFORM_DEVICE(dev);
    SysBusDevice *sbdev = SYS_BUS_DEVICE(dev);
    VFIODevice *vbasedev = &vdev->vbasedev;
    int i, ret;

    vbasedev->type = VFIO_DEVICE_TYPE_PLATFORM;
    vbasedev->dev = dev;
    vbasedev->ops = &vfio_platform_ops;

    qemu_mutex_init(&vdev->intp_mutex);

    trace_vfio_platform_realize(vbasedev->sysfsdev ?
                                vbasedev->sysfsdev : vbasedev->name,
                                vdev->compat);

    ret = vfio_base_device_init(vbasedev, errp);
    if (ret) {
        goto out;
    }

    for (i = 0; i < vbasedev->num_regions; i++) {
        if (vfio_region_mmap(vdev->regions[i])) {
            error_report("%s mmap unsupported. Performance may be slow",
                         memory_region_name(vdev->regions[i]->mem));
        }
        sysbus_init_mmio(sbdev, vdev->regions[i]->mem);
    }
out:
    if (!ret) {
        return;
    }

    if (vdev->vbasedev.name) {
        error_prepend(errp, ERR_PREFIX, vdev->vbasedev.name);
    } else {
        error_prepend(errp, "vfio error: ");
    }
}

static const VMStateDescription vfio_platform_vmstate = {
    .name = TYPE_VFIO_PLATFORM,
    .unmigratable = 1,
};

static Property vfio_platform_dev_properties[] = {
    DEFINE_PROP_STRING("host", VFIOPlatformDevice, vbasedev.name),
    DEFINE_PROP_STRING("sysfsdev", VFIOPlatformDevice, vbasedev.sysfsdev),
    DEFINE_PROP_BOOL("x-no-mmap", VFIOPlatformDevice, vbasedev.no_mmap, false),
    DEFINE_PROP_UINT32("mmap-timeout-ms", VFIOPlatformDevice,
                       mmap_timeout, 1100),
    DEFINE_PROP_BOOL("x-irqfd", VFIOPlatformDevice, irqfd_allowed, true),
    DEFINE_PROP_END_OF_LIST(),
};

static void vfio_platform_class_init(ObjectClass *klass, void *data)
{
    DeviceClass *dc = DEVICE_CLASS(klass);
    SysBusDeviceClass *sbc = SYS_BUS_DEVICE_CLASS(klass);

    dc->realize = vfio_platform_realize;
    dc->props = vfio_platform_dev_properties;
    dc->vmsd = &vfio_platform_vmstate;
    dc->desc = "VFIO-based platform device assignment";
    sbc->connect_irq_notifier = vfio_start_irqfd_injection;
    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
}

static const TypeInfo vfio_platform_dev_info = {
    .name = TYPE_VFIO_PLATFORM,
    .parent = TYPE_SYS_BUS_DEVICE,
    .instance_size = sizeof(VFIOPlatformDevice),
    .class_init = vfio_platform_class_init,
    .class_size = sizeof(VFIOPlatformDeviceClass),
    .abstract   = true,
};

static void register_vfio_platform_dev_type(void)
{
    type_register_static(&vfio_platform_dev_info);
}

type_init(register_vfio_platform_dev_type)