// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend - Provides restricted access to the real PCI bus topology
 *               to the frontend
 *
 *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

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

struct passthrough_dev_data {
        /* Access to dev_list must be protected by lock */
        struct list_head dev_list;
        struct mutex lock;
};

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

        mutex_lock(&dev_data->lock);

        list_for_each_entry(dev_entry, &dev_data->dev_list, list) {
                if (domain == (unsigned int)pci_domain_nr(dev_entry->dev->bus)
                    && bus == (unsigned int)dev_entry->dev->bus->number
                    && devfn == dev_entry->dev->devfn) {
                        dev = dev_entry->dev;
                        break;
                }
        }

        mutex_unlock(&dev_data->lock);

        return dev;
}

static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
                                   struct pci_dev *dev,
                                   int devid, publish_pci_dev_cb publish_cb)
{
        struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
        struct pci_dev_entry *dev_entry;
        unsigned int domain, bus, devfn;
        int err;

        dev_entry = kmalloc_obj(*dev_entry);
        if (!dev_entry)
                return -ENOMEM;
        dev_entry->dev = dev;

        mutex_lock(&dev_data->lock);
        list_add_tail(&dev_entry->list, &dev_data->dev_list);
        mutex_unlock(&dev_data->lock);

        /* Publish this device. */
        domain = (unsigned int)pci_domain_nr(dev->bus);
        bus = (unsigned int)dev->bus->number;
        devfn = dev->devfn;
        err = publish_cb(pdev, domain, bus, devfn, devid);

        return err;
}

static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
                                        struct pci_dev *dev, bool lock)
{
        struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
        struct pci_dev_entry *dev_entry, *t;
        struct pci_dev *found_dev = NULL;

        mutex_lock(&dev_data->lock);

        list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
                if (dev_entry->dev == dev) {
                        list_del(&dev_entry->list);
                        found_dev = dev_entry->dev;
                        kfree(dev_entry);
                }
        }

        mutex_unlock(&dev_data->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)
{
        struct passthrough_dev_data *dev_data;

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

        mutex_init(&dev_data->lock);

        INIT_LIST_HEAD(&dev_data->dev_list);

        pdev->pci_dev_data = dev_data;

        return 0;
}

static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
                                         publish_pci_root_cb publish_root_cb)
{
        int err = 0;
        struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
        struct pci_dev_entry *dev_entry, *e;
        struct pci_dev *dev;
        int found;
        unsigned int domain, bus;

        mutex_lock(&dev_data->lock);

        list_for_each_entry(dev_entry, &dev_data->dev_list, list) {
                /* Only publish this device as a root if none of its
                 * parent bridges are exported
                 */
                found = 0;
                dev = dev_entry->dev->bus->self;
                for (; !found && dev != NULL; dev = dev->bus->self) {
                        list_for_each_entry(e, &dev_data->dev_list, list) {
                                if (dev == e->dev) {
                                        found = 1;
                                        break;
                                }
                        }
                }

                domain = (unsigned int)pci_domain_nr(dev_entry->dev->bus);
                bus = (unsigned int)dev_entry->dev->bus->number;

                if (!found) {
                        err = publish_root_cb(pdev, domain, bus);
                        if (err)
                                break;
                }
        }

        mutex_unlock(&dev_data->lock);

        return err;
}

static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
{
        struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
        struct pci_dev_entry *dev_entry, *t;

        list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
                struct pci_dev *dev = dev_entry->dev;
                list_del(&dev_entry->list);
                device_lock(&dev->dev);
                pcistub_put_pci_dev(dev);
                device_unlock(&dev->dev);
                kfree(dev_entry);
        }

        kfree(dev_data);
        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)
{
        *domain = pci_domain_nr(pcidev->bus);
        *bus = pcidev->bus->number;
        *devfn = pcidev->devfn;
        return 1;
}

const struct xen_pcibk_backend xen_pcibk_passthrough_backend = {
        .name           = "passthrough",
        .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,
};