// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend - Provides a Virtual PCI bus (with real devices)
 *               to the frontend
 *
 *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#define dev_fmt pr_fmt

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/mutex.h>
#include "pciback.h"

#define PCI_SLOT_MAX 32

struct vpci_dev_data {
        /* Access to dev_list must be protected by lock */
        struct list_head dev_list[PCI_SLOT_MAX];
        struct mutex lock;
};

static inline struct list_head *list_first(struct list_head *head)
{
        return head->next;
}

static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev,
                                               unsigned int domain,
                                               unsigned int bus,
                                               unsigned int devfn)
{
        struct pci_dev_entry *entry;
        struct pci_dev *dev = NULL;
        struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;

        if (domain != 0 || bus != 0)
                return NULL;

        if (PCI_SLOT(devfn) < PCI_SLOT_MAX) {
                mutex_lock(&vpci_dev->lock);

                list_for_each_entry(entry,
                                    &vpci_dev->dev_list[PCI_SLOT(devfn)],
                                    list) {
                        if (PCI_FUNC(entry->dev->devfn) == PCI_FUNC(devfn)) {
                                dev = entry->dev;
                                break;
                        }
                }

                mutex_unlock(&vpci_dev->lock);
        }
        return dev;
}

static inline int match_slot(struct pci_dev *l, struct pci_dev *r)
{
        if (pci_domain_nr(l->bus) == pci_domain_nr(r->bus)
            && l->bus == r->bus && PCI_SLOT(l->devfn) == PCI_SLOT(r->devfn))
                return 1;

        return 0;
}

static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
                                   struct pci_dev *dev, int devid,
                                   publish_pci_dev_cb publish_cb)
{
        int err = 0, slot, func = PCI_FUNC(dev->devfn);
        struct pci_dev_entry *t, *dev_entry;
        struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;

        if ((dev->class >> 24) == PCI_BASE_CLASS_BRIDGE) {
                err = -EFAULT;
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Can't export bridges on the virtual PCI bus");
                goto out;
        }

        dev_entry = kmalloc_obj(*dev_entry);
        if (!dev_entry) {
                err = -ENOMEM;
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error adding entry to virtual PCI bus");
                goto out;
        }

        dev_entry->dev = dev;

        mutex_lock(&vpci_dev->lock);

        /*
         * Keep multi-function devices together on the virtual PCI bus, except
         * that we want to keep virtual functions at func 0 on their own. They
         * aren't multi-function devices and hence their presence at func 0
         * may cause guests to not scan the other functions.
         */
        if (!dev->is_virtfn || func) {
                for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
                        if (list_empty(&vpci_dev->dev_list[slot]))
                                continue;

                        t = list_entry(list_first(&vpci_dev->dev_list[slot]),
                                       struct pci_dev_entry, list);
                        if (t->dev->is_virtfn && !PCI_FUNC(t->dev->devfn))
                                continue;

                        if (match_slot(dev, t->dev)) {
                                dev_info(&dev->dev, "vpci: assign to virtual slot %d func %d\n",
                                         slot, func);
                                list_add_tail(&dev_entry->list,
                                              &vpci_dev->dev_list[slot]);
                                goto unlock;
                        }
                }
        }

        /* Assign to a new slot on the virtual PCI bus */
        for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
                if (list_empty(&vpci_dev->dev_list[slot])) {
                        dev_info(&dev->dev, "vpci: assign to virtual slot %d\n",
                                 slot);
                        list_add_tail(&dev_entry->list,
                                      &vpci_dev->dev_list[slot]);
                        goto unlock;
                }
        }

        err = -ENOMEM;
        xenbus_dev_fatal(pdev->xdev, err,
                         "No more space on root virtual PCI bus");

unlock:
        mutex_unlock(&vpci_dev->lock);

        /* Publish this device. */
        if (!err)
                err = publish_cb(pdev, 0, 0, PCI_DEVFN(slot, func), devid);
        else
                kfree(dev_entry);

out:
        return err;
}

static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
                                        struct pci_dev *dev, bool lock)
{
        int slot;
        struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
        struct pci_dev *found_dev = NULL;

        mutex_lock(&vpci_dev->lock);

        for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
                struct pci_dev_entry *e;

                list_for_each_entry(e, &vpci_dev->dev_list[slot], list) {
                        if (e->dev == dev) {
                                list_del(&e->list);
                                found_dev = e->dev;
                                kfree(e);
                                goto out;
                        }
                }
        }

out:
        mutex_unlock(&vpci_dev->lock);

        if (found_dev) {
                if (lock)
                        device_lock(&found_dev->dev);
                pcistub_put_pci_dev(found_dev);
                if (lock)
                        device_unlock(&found_dev->dev);
        }
}

static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
{
        int slot;
        struct vpci_dev_data *vpci_dev;

        vpci_dev = kmalloc_obj(*vpci_dev);
        if (!vpci_dev)
                return -ENOMEM;

        mutex_init(&vpci_dev->lock);

        for (slot = 0; slot < PCI_SLOT_MAX; slot++)
                INIT_LIST_HEAD(&vpci_dev->dev_list[slot]);

        pdev->pci_dev_data = vpci_dev;

        return 0;
}

static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
                                         publish_pci_root_cb publish_cb)
{
        /* The Virtual PCI bus has only one root */
        return publish_cb(pdev, 0, 0);
}

static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
{
        int slot;
        struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;

        for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
                struct pci_dev_entry *e, *tmp;
                list_for_each_entry_safe(e, tmp, &vpci_dev->dev_list[slot],
                                         list) {
                        struct pci_dev *dev = e->dev;
                        list_del(&e->list);
                        device_lock(&dev->dev);
                        pcistub_put_pci_dev(dev);
                        device_unlock(&dev->dev);
                        kfree(e);
                }
        }

        kfree(vpci_dev);
        pdev->pci_dev_data = NULL;
}

static int __xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
                                        struct xen_pcibk_device *pdev,
                                        unsigned int *domain, unsigned int *bus,
                                        unsigned int *devfn)
{
        struct pci_dev_entry *entry;
        struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
        int found = 0, slot;

        mutex_lock(&vpci_dev->lock);
        for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
                list_for_each_entry(entry,
                            &vpci_dev->dev_list[slot],
                            list) {
                        if (entry->dev == pcidev) {
                                found = 1;
                                *domain = 0;
                                *bus = 0;
                                *devfn = PCI_DEVFN(slot,
                                         PCI_FUNC(pcidev->devfn));
                        }
                }
        }
        mutex_unlock(&vpci_dev->lock);
        return found;
}

const struct xen_pcibk_backend xen_pcibk_vpci_backend = {
        .name           = "vpci",
        .init           = __xen_pcibk_init_devices,
        .free           = __xen_pcibk_release_devices,
        .find           = __xen_pcibk_get_pcifront_dev,
        .publish        = __xen_pcibk_publish_pci_roots,
        .release        = __xen_pcibk_release_pci_dev,
        .add            = __xen_pcibk_add_pci_dev,
        .get            = __xen_pcibk_get_pci_dev,
};