/*
 * Virtio PCI driver - modern (virtio 1.0) device support
 *
 * This module allows virtio devices to be used over a virtual PCI device.
 * This can be used with QEMU based VMMs like KVM or Xen.
 *
 * Copyright IBM Corp. 2007
 * Copyright Red Hat, Inc. 2014
 *
 * Authors:
 *  Anthony Liguori  <aliguori@us.ibm.com>
 *  Rusty Russell <rusty@rustcorp.com.au>
 *  Michael S. Tsirkin <mst@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#include <linux/delay.h>
#define VIRTIO_PCI_NO_LEGACY
#include "virtio_pci_common.h"

/*
 * Type-safe wrappers for io accesses.
 * Use these to enforce at compile time the following spec requirement:
 *
 * The driver MUST access each field using the “natural” access
 * method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses
 * for 16-bit fields and 8-bit accesses for 8-bit fields.
 */
static inline u8 vp_ioread8(u8 __iomem *addr)
{
        return ioread8(addr);
}
static inline u16 vp_ioread16 (__le16 __iomem *addr)
{
        return ioread16(addr);
}

static inline u32 vp_ioread32(__le32 __iomem *addr)
{
        return ioread32(addr);
}

static inline void vp_iowrite8(u8 value, u8 __iomem *addr)
{
        iowrite8(value, addr);
}

static inline void vp_iowrite16(u16 value, __le16 __iomem *addr)
{
        iowrite16(value, addr);
}

static inline void vp_iowrite32(u32 value, __le32 __iomem *addr)
{
        iowrite32(value, addr);
}

static void vp_iowrite64_twopart(u64 val,
                                 __le32 __iomem *lo, __le32 __iomem *hi)
{
        vp_iowrite32((u32)val, lo);
        vp_iowrite32(val >> 32, hi);
}

static void __iomem *map_capability(struct pci_dev *dev, int off,
                                    size_t minlen,
                                    u32 align,
                                    u32 start, u32 size,
                                    size_t *len)
{
        u8 bar;
        u32 offset, length;
        void __iomem *p;

        pci_read_config_byte(dev, off + offsetof(struct virtio_pci_cap,
                                                 bar),
                             &bar);
        pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, offset),
                             &offset);
        pci_read_config_dword(dev, off + offsetof(struct virtio_pci_cap, length),
                              &length);

        if (length <= start) {
                dev_err(&dev->dev,
                        "virtio_pci: bad capability len %u (>%u expected)\n",
                        length, start);
                return NULL;
        }

        if (length - start < minlen) {
                dev_err(&dev->dev,
                        "virtio_pci: bad capability len %u (>=%zu expected)\n",
                        length, minlen);
                return NULL;
        }

        length -= start;

        if (start + offset < offset) {
                dev_err(&dev->dev,
                        "virtio_pci: map wrap-around %u+%u\n",
                        start, offset);
                return NULL;
        }

        offset += start;

        if (offset & (align - 1)) {
                dev_err(&dev->dev,
                        "virtio_pci: offset %u not aligned to %u\n",
                        offset, align);
                return NULL;
        }

        if (length > size)
                length = size;

        if (len)
                *len = length;

        if (minlen + offset < minlen ||
            minlen + offset > pci_resource_len(dev, bar)) {
                dev_err(&dev->dev,
                        "virtio_pci: map virtio %zu@%u "
                        "out of range on bar %i length %lu\n",
                        minlen, offset,
                        bar, (unsigned long)pci_resource_len(dev, bar));
                return NULL;
        }

        p = pci_iomap_range(dev, bar, offset, length);
        if (!p)
                dev_err(&dev->dev,
                        "virtio_pci: unable to map virtio %u@%u on bar %i\n",
                        length, offset, bar);
        return p;
}

/* virtio config->get_features() implementation */
static u64 vp_get_features(struct virtio_device *vdev)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        u64 features;

        vp_iowrite32(0, &vp_dev->common->device_feature_select);
        features = vp_ioread32(&vp_dev->common->device_feature);
        vp_iowrite32(1, &vp_dev->common->device_feature_select);
        features |= ((u64)vp_ioread32(&vp_dev->common->device_feature) << 32);

        return features;
}

/* virtio config->finalize_features() implementation */
static int vp_finalize_features(struct virtio_device *vdev)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);

        /* Give virtio_ring a chance to accept features. */
        vring_transport_features(vdev);

        if (!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
                dev_err(&vdev->dev, "virtio: device uses modern interface "
                        "but does not have VIRTIO_F_VERSION_1\n");
                return -EINVAL;
        }

        vp_iowrite32(0, &vp_dev->common->guest_feature_select);
        vp_iowrite32((u32)vdev->features, &vp_dev->common->guest_feature);
        vp_iowrite32(1, &vp_dev->common->guest_feature_select);
        vp_iowrite32(vdev->features >> 32, &vp_dev->common->guest_feature);

        return 0;
}

/* virtio config->get() implementation */
static void vp_get(struct virtio_device *vdev, unsigned offset,
                   void *buf, unsigned len)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        u8 b;
        __le16 w;
        __le32 l;

        BUG_ON(offset + len > vp_dev->device_len);

        switch (len) {
        case 1:
                b = ioread8(vp_dev->device + offset);
                memcpy(buf, &b, sizeof b);
                break;
        case 2:
                w = cpu_to_le16(ioread16(vp_dev->device + offset));
                memcpy(buf, &w, sizeof w);
                break;
        case 4:
                l = cpu_to_le32(ioread32(vp_dev->device + offset));
                memcpy(buf, &l, sizeof l);
                break;
        case 8:
                l = cpu_to_le32(ioread32(vp_dev->device + offset));
                memcpy(buf, &l, sizeof l);
                l = cpu_to_le32(ioread32(vp_dev->device + offset + sizeof l));
                memcpy(buf + sizeof l, &l, sizeof l);
                break;
        default:
                BUG();
        }
}

/* the config->set() implementation.  it's symmetric to the config->get()
 * implementation */
static void vp_set(struct virtio_device *vdev, unsigned offset,
                   const void *buf, unsigned len)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        u8 b;
        __le16 w;
        __le32 l;

        BUG_ON(offset + len > vp_dev->device_len);

        switch (len) {
        case 1:
                memcpy(&b, buf, sizeof b);
                iowrite8(b, vp_dev->device + offset);
                break;
        case 2:
                memcpy(&w, buf, sizeof w);
                iowrite16(le16_to_cpu(w), vp_dev->device + offset);
                break;
        case 4:
                memcpy(&l, buf, sizeof l);
                iowrite32(le32_to_cpu(l), vp_dev->device + offset);
                break;
        case 8:
                memcpy(&l, buf, sizeof l);
                iowrite32(le32_to_cpu(l), vp_dev->device + offset);
                memcpy(&l, buf + sizeof l, sizeof l);
                iowrite32(le32_to_cpu(l), vp_dev->device + offset + sizeof l);
                break;
        default:
                BUG();
        }
}

static u32 vp_generation(struct virtio_device *vdev)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        return vp_ioread8(&vp_dev->common->config_generation);
}

/* config->{get,set}_status() implementations */
static u8 vp_get_status(struct virtio_device *vdev)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        return vp_ioread8(&vp_dev->common->device_status);
}

static void vp_set_status(struct virtio_device *vdev, u8 status)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        /* We should never be setting status to 0. */
        BUG_ON(status == 0);
        vp_iowrite8(status, &vp_dev->common->device_status);
}

static void vp_reset(struct virtio_device *vdev)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        /* 0 status means a reset. */
        vp_iowrite8(0, &vp_dev->common->device_status);
        /* After writing 0 to device_status, the driver MUST wait for a read of
         * device_status to return 0 before reinitializing the device.
         * This will flush out the status write, and flush in device writes,
         * including MSI-X interrupts, if any.
         */
        while (vp_ioread8(&vp_dev->common->device_status))
                msleep(1);
        /* Flush pending VQ/configuration callbacks. */
        vp_synchronize_vectors(vdev);
}

static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
{
        /* Setup the vector used for configuration events */
        vp_iowrite16(vector, &vp_dev->common->msix_config);
        /* Verify we had enough resources to assign the vector */
        /* Will also flush the write out to device */
        return vp_ioread16(&vp_dev->common->msix_config);
}

static struct virtqueue *setup_vq(struct virtio_pci_device *vp_dev,
                                  struct virtio_pci_vq_info *info,
                                  unsigned index,
                                  void (*callback)(struct virtqueue *vq),
                                  const char *name,
                                  bool ctx,
                                  u16 msix_vec)
{
        struct virtio_pci_common_cfg __iomem *cfg = vp_dev->common;
        struct virtqueue *vq;
        u16 num, off;
        int err;

        if (index >= vp_ioread16(&cfg->num_queues))
                return ERR_PTR(-ENOENT);

        /* Select the queue we're interested in */
        vp_iowrite16(index, &cfg->queue_select);

        /* Check if queue is either not available or already active. */
        num = vp_ioread16(&cfg->queue_size);
        if (!num || vp_ioread16(&cfg->queue_enable))
                return ERR_PTR(-ENOENT);

        if (num & (num - 1)) {
                dev_warn(&vp_dev->pci_dev->dev, "bad queue size %u", num);
                return ERR_PTR(-EINVAL);
        }

        /* get offset of notification word for this vq */
        off = vp_ioread16(&cfg->queue_notify_off);

        info->msix_vector = msix_vec;

        /* create the vring */
        vq = vring_create_virtqueue(index, num,
                                    SMP_CACHE_BYTES, &vp_dev->vdev,
                                    true, true, ctx,
                                    vp_notify, callback, name);
        if (!vq)
                return ERR_PTR(-ENOMEM);

        /* activate the queue */
        vp_iowrite16(virtqueue_get_vring_size(vq), &cfg->queue_size);
        vp_iowrite64_twopart(virtqueue_get_desc_addr(vq),
                             &cfg->queue_desc_lo, &cfg->queue_desc_hi);
        vp_iowrite64_twopart(virtqueue_get_avail_addr(vq),
                             &cfg->queue_avail_lo, &cfg->queue_avail_hi);
        vp_iowrite64_twopart(virtqueue_get_used_addr(vq),
                             &cfg->queue_used_lo, &cfg->queue_used_hi);

        if (vp_dev->notify_base) {
                /* offset should not wrap */
                if ((u64)off * vp_dev->notify_offset_multiplier + 2
                    > vp_dev->notify_len) {
                        dev_warn(&vp_dev->pci_dev->dev,
                                 "bad notification offset %u (x %u) "
                                 "for queue %u > %zd",
                                 off, vp_dev->notify_offset_multiplier,
                                 index, vp_dev->notify_len);
                        err = -EINVAL;
                        goto err_map_notify;
                }
                vq->priv = (void __force *)vp_dev->notify_base +
                        off * vp_dev->notify_offset_multiplier;
        } else {
                vq->priv = (void __force *)map_capability(vp_dev->pci_dev,
                                          vp_dev->notify_map_cap, 2, 2,
                                          off * vp_dev->notify_offset_multiplier, 2,
                                          NULL);
        }

        if (!vq->priv) {
                err = -ENOMEM;
                goto err_map_notify;
        }

        if (msix_vec != VIRTIO_MSI_NO_VECTOR) {
                vp_iowrite16(msix_vec, &cfg->queue_msix_vector);
                msix_vec = vp_ioread16(&cfg->queue_msix_vector);
                if (msix_vec == VIRTIO_MSI_NO_VECTOR) {
                        err = -EBUSY;
                        goto err_assign_vector;
                }
        }

        return vq;

err_assign_vector:
        if (!vp_dev->notify_base)
                pci_iounmap(vp_dev->pci_dev, (void __iomem __force *)vq->priv);
err_map_notify:
        vring_del_virtqueue(vq);
        return ERR_PTR(err);
}

static int vp_modern_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                              struct virtqueue *vqs[],
                              vq_callback_t *callbacks[],
                              const char * const names[], const bool *ctx,
                              struct irq_affinity *desc)
{
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        struct virtqueue *vq;
        int rc = vp_find_vqs(vdev, nvqs, vqs, callbacks, names, ctx, desc);

        if (rc)
                return rc;

        /* Select and activate all queues. Has to be done last: once we do
         * this, there's no way to go back except reset.
         */
        list_for_each_entry(vq, &vdev->vqs, list) {
                vp_iowrite16(vq->index, &vp_dev->common->queue_select);
                vp_iowrite16(1, &vp_dev->common->queue_enable);
        }

        return 0;
}

static void del_vq(struct virtio_pci_vq_info *info)
{
        struct virtqueue *vq = info->vq;
        struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);

        vp_iowrite16(vq->index, &vp_dev->common->queue_select);

        if (vp_dev->msix_enabled) {
                vp_iowrite16(VIRTIO_MSI_NO_VECTOR,
                             &vp_dev->common->queue_msix_vector);
                /* Flush the write out to device */
                vp_ioread16(&vp_dev->common->queue_msix_vector);
        }

        if (!vp_dev->notify_base)
                pci_iounmap(vp_dev->pci_dev, (void __force __iomem *)vq->priv);

        vring_del_virtqueue(vq);
}

static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
        .get            = NULL,
        .set            = NULL,
        .generation     = vp_generation,
        .get_status     = vp_get_status,
        .set_status     = vp_set_status,
        .reset          = vp_reset,
        .find_vqs       = vp_modern_find_vqs,
        .del_vqs        = vp_del_vqs,
        .get_features   = vp_get_features,
        .finalize_features = vp_finalize_features,
        .bus_name       = vp_bus_name,
        .set_vq_affinity = vp_set_vq_affinity,
        .get_vq_affinity = vp_get_vq_affinity,
};

static const struct virtio_config_ops virtio_pci_config_ops = {
        .get            = vp_get,
        .set            = vp_set,
        .generation     = vp_generation,
        .get_status     = vp_get_status,
        .set_status     = vp_set_status,
        .reset          = vp_reset,
        .find_vqs       = vp_modern_find_vqs,
        .del_vqs        = vp_del_vqs,
        .get_features   = vp_get_features,
        .finalize_features = vp_finalize_features,
        .bus_name       = vp_bus_name,
        .set_vq_affinity = vp_set_vq_affinity,
        .get_vq_affinity = vp_get_vq_affinity,
};

/**
 * virtio_pci_find_capability - walk capabilities to find device info.
 * @dev: the pci device
 * @cfg_type: the VIRTIO_PCI_CAP_* value we seek
 * @ioresource_types: IORESOURCE_MEM and/or IORESOURCE_IO.
 *
 * Returns offset of the capability, or 0.
 */
static inline int virtio_pci_find_capability(struct pci_dev *dev, u8 cfg_type,
                                             u32 ioresource_types, int *bars)
{
        int pos;

        for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
             pos > 0;
             pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
                u8 type, bar;
                pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
                                                         cfg_type),
                                     &type);
                pci_read_config_byte(dev, pos + offsetof(struct virtio_pci_cap,
                                                         bar),
                                     &bar);

                /* Ignore structures with reserved BAR values */
                if (bar > 0x5)
                        continue;

                if (type == cfg_type) {
                        if (pci_resource_len(dev, bar) &&
                            pci_resource_flags(dev, bar) & ioresource_types) {
                                *bars |= (1 << bar);
                                return pos;
                        }
                }
        }
        return 0;
}

/* This is part of the ABI.  Don't screw with it. */
static inline void check_offsets(void)
{
        /* Note: disk space was harmed in compilation of this function. */
        BUILD_BUG_ON(VIRTIO_PCI_CAP_VNDR !=
                     offsetof(struct virtio_pci_cap, cap_vndr));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_NEXT !=
                     offsetof(struct virtio_pci_cap, cap_next));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_LEN !=
                     offsetof(struct virtio_pci_cap, cap_len));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_CFG_TYPE !=
                     offsetof(struct virtio_pci_cap, cfg_type));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_BAR !=
                     offsetof(struct virtio_pci_cap, bar));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_OFFSET !=
                     offsetof(struct virtio_pci_cap, offset));
        BUILD_BUG_ON(VIRTIO_PCI_CAP_LENGTH !=
                     offsetof(struct virtio_pci_cap, length));
        BUILD_BUG_ON(VIRTIO_PCI_NOTIFY_CAP_MULT !=
                     offsetof(struct virtio_pci_notify_cap,
                              notify_off_multiplier));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_DFSELECT !=
                     offsetof(struct virtio_pci_common_cfg,
                              device_feature_select));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_DF !=
                     offsetof(struct virtio_pci_common_cfg, device_feature));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_GFSELECT !=
                     offsetof(struct virtio_pci_common_cfg,
                              guest_feature_select));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_GF !=
                     offsetof(struct virtio_pci_common_cfg, guest_feature));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_MSIX !=
                     offsetof(struct virtio_pci_common_cfg, msix_config));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_NUMQ !=
                     offsetof(struct virtio_pci_common_cfg, num_queues));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_STATUS !=
                     offsetof(struct virtio_pci_common_cfg, device_status));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_CFGGENERATION !=
                     offsetof(struct virtio_pci_common_cfg, config_generation));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_SELECT !=
                     offsetof(struct virtio_pci_common_cfg, queue_select));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_SIZE !=
                     offsetof(struct virtio_pci_common_cfg, queue_size));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_MSIX !=
                     offsetof(struct virtio_pci_common_cfg, queue_msix_vector));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_ENABLE !=
                     offsetof(struct virtio_pci_common_cfg, queue_enable));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_NOFF !=
                     offsetof(struct virtio_pci_common_cfg, queue_notify_off));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_DESCLO !=
                     offsetof(struct virtio_pci_common_cfg, queue_desc_lo));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_DESCHI !=
                     offsetof(struct virtio_pci_common_cfg, queue_desc_hi));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_AVAILLO !=
                     offsetof(struct virtio_pci_common_cfg, queue_avail_lo));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_AVAILHI !=
                     offsetof(struct virtio_pci_common_cfg, queue_avail_hi));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_USEDLO !=
                     offsetof(struct virtio_pci_common_cfg, queue_used_lo));
        BUILD_BUG_ON(VIRTIO_PCI_COMMON_Q_USEDHI !=
                     offsetof(struct virtio_pci_common_cfg, queue_used_hi));
}

/* the PCI probing function */
int virtio_pci_modern_probe(struct virtio_pci_device *vp_dev)
{
        struct pci_dev *pci_dev = vp_dev->pci_dev;
        int err, common, isr, notify, device;
        u32 notify_length;
        u32 notify_offset;

        check_offsets();

        /* We only own devices >= 0x1000 and <= 0x107f: leave the rest. */
        if (pci_dev->device < 0x1000 || pci_dev->device > 0x107f)
                return -ENODEV;

        if (pci_dev->device < 0x1040) {
                /* Transitional devices: use the PCI subsystem device id as
                 * virtio device id, same as legacy driver always did.
                 */
                vp_dev->vdev.id.device = pci_dev->subsystem_device;
        } else {
                /* Modern devices: simply use PCI device id, but start from 0x1040. */
                vp_dev->vdev.id.device = pci_dev->device - 0x1040;
        }
        vp_dev->vdev.id.vendor = pci_dev->subsystem_vendor;

        /* check for a common config: if not, use legacy mode (bar 0). */
        common = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_COMMON_CFG,
                                            IORESOURCE_IO | IORESOURCE_MEM,
                                            &vp_dev->modern_bars);
        if (!common) {
                dev_info(&pci_dev->dev,
                         "virtio_pci: leaving for legacy driver\n");
                return -ENODEV;
        }

        /* If common is there, these should be too... */
        isr = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_ISR_CFG,
                                         IORESOURCE_IO | IORESOURCE_MEM,
                                         &vp_dev->modern_bars);
        notify = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_NOTIFY_CFG,
                                            IORESOURCE_IO | IORESOURCE_MEM,
                                            &vp_dev->modern_bars);
        if (!isr || !notify) {
                dev_err(&pci_dev->dev,
                        "virtio_pci: missing capabilities %i/%i/%i\n",
                        common, isr, notify);
                return -EINVAL;
        }

        err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
        if (err)
                err = dma_set_mask_and_coherent(&pci_dev->dev,
                                                DMA_BIT_MASK(32));
        if (err)
                dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");

        /* Device capability is only mandatory for devices that have
         * device-specific configuration.
         */
        device = virtio_pci_find_capability(pci_dev, VIRTIO_PCI_CAP_DEVICE_CFG,
                                            IORESOURCE_IO | IORESOURCE_MEM,
                                            &vp_dev->modern_bars);

        err = pci_request_selected_regions(pci_dev, vp_dev->modern_bars,
                                           "virtio-pci-modern");
        if (err)
                return err;

        err = -EINVAL;
        vp_dev->common = map_capability(pci_dev, common,
                                        sizeof(struct virtio_pci_common_cfg), 4,
                                        0, sizeof(struct virtio_pci_common_cfg),
                                        NULL);
        if (!vp_dev->common)
                goto err_map_common;
        vp_dev->isr = map_capability(pci_dev, isr, sizeof(u8), 1,
                                     0, 1,
                                     NULL);
        if (!vp_dev->isr)
                goto err_map_isr;

        /* Read notify_off_multiplier from config space. */
        pci_read_config_dword(pci_dev,
                              notify + offsetof(struct virtio_pci_notify_cap,
                                                notify_off_multiplier),
                              &vp_dev->notify_offset_multiplier);
        /* Read notify length and offset from config space. */
        pci_read_config_dword(pci_dev,
                              notify + offsetof(struct virtio_pci_notify_cap,
                                                cap.length),
                              &notify_length);

        pci_read_config_dword(pci_dev,
                              notify + offsetof(struct virtio_pci_notify_cap,
                                                cap.offset),
                              &notify_offset);

        /* We don't know how many VQs we'll map, ahead of the time.
         * If notify length is small, map it all now.
         * Otherwise, map each VQ individually later.
         */
        if ((u64)notify_length + (notify_offset % PAGE_SIZE) <= PAGE_SIZE) {
                vp_dev->notify_base = map_capability(pci_dev, notify, 2, 2,
                                                     0, notify_length,
                                                     &vp_dev->notify_len);
                if (!vp_dev->notify_base)
                        goto err_map_notify;
        } else {
                vp_dev->notify_map_cap = notify;
        }

        /* Again, we don't know how much we should map, but PAGE_SIZE
         * is more than enough for all existing devices.
         */
        if (device) {
                vp_dev->device = map_capability(pci_dev, device, 0, 4,
                                                0, PAGE_SIZE,
                                                &vp_dev->device_len);
                if (!vp_dev->device)
                        goto err_map_device;

                vp_dev->vdev.config = &virtio_pci_config_ops;
        } else {
                vp_dev->vdev.config = &virtio_pci_config_nodev_ops;
        }

        vp_dev->config_vector = vp_config_vector;
        vp_dev->setup_vq = setup_vq;
        vp_dev->del_vq = del_vq;

        return 0;

err_map_device:
        if (vp_dev->notify_base)
                pci_iounmap(pci_dev, vp_dev->notify_base);
err_map_notify:
        pci_iounmap(pci_dev, vp_dev->isr);
err_map_isr:
        pci_iounmap(pci_dev, vp_dev->common);
err_map_common:
        return err;
}

void virtio_pci_modern_remove(struct virtio_pci_device *vp_dev)
{
        struct pci_dev *pci_dev = vp_dev->pci_dev;

        if (vp_dev->device)
                pci_iounmap(pci_dev, vp_dev->device);
        if (vp_dev->notify_base)
                pci_iounmap(pci_dev, vp_dev->notify_base);
        pci_iounmap(pci_dev, vp_dev->isr);
        pci_iounmap(pci_dev, vp_dev->common);
        pci_release_selected_regions(pci_dev, vp_dev->modern_bars);
}