// SPDX-License-Identifier: GPL-2.0
/*
 * PCI Backend Xenbus Setup - handles setup with frontend and xend
 *
 *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/workqueue.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/pci.h>
#include "pciback.h"

#define INVALID_EVTCHN_IRQ  (-1)

static bool __read_mostly passthrough;
module_param(passthrough, bool, S_IRUGO);
MODULE_PARM_DESC(passthrough,
        "Option to specify how to export PCI topology to guest:\n"\
        " 0 - (default) Hide the true PCI topology and makes the frontend\n"\
        "   there is a single PCI bus with only the exported devices on it.\n"\
        "   For example, a device at 03:05.0 will be re-assigned to 00:00.0\n"\
        "   while second device at 02:1a.1 will be re-assigned to 00:01.1.\n"\
        " 1 - Passthrough provides a real view of the PCI topology to the\n"\
        "   frontend (for example, a device at 06:01.b will still appear at\n"\
        "   06:01.b to the frontend). This is similar to how Xen 2.0.x\n"\
        "   exposed PCI devices to its driver domains. This may be required\n"\
        "   for drivers which depend on finding their hardware in certain\n"\
        "   bus/slot locations.");

static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev)
{
        struct xen_pcibk_device *pdev;

        pdev = kzalloc_obj(struct xen_pcibk_device);
        if (pdev == NULL)
                goto out;
        dev_dbg(&xdev->dev, "allocated pdev @ 0x%p\n", pdev);

        pdev->xdev = xdev;

        mutex_init(&pdev->dev_lock);

        pdev->sh_info = NULL;
        pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
        pdev->be_watching = 0;

        INIT_WORK(&pdev->op_work, xen_pcibk_do_op);

        if (xen_pcibk_init_devices(pdev)) {
                kfree(pdev);
                pdev = NULL;
        }

        dev_set_drvdata(&xdev->dev, pdev);

out:
        return pdev;
}

static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)
{
        mutex_lock(&pdev->dev_lock);
        /* Ensure the guest can't trigger our handler before removing devices */
        if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {
                unbind_from_irqhandler(pdev->evtchn_irq, pdev);
                pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
        }

        /* If the driver domain started an op, make sure we complete it
         * before releasing the shared memory */

        flush_work(&pdev->op_work);

        if (pdev->sh_info != NULL) {
                xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);
                pdev->sh_info = NULL;
        }
        mutex_unlock(&pdev->dev_lock);
}

static void free_pdev(struct xen_pcibk_device *pdev)
{
        if (pdev->be_watching) {
                unregister_xenbus_watch(&pdev->be_watch);
                pdev->be_watching = 0;
        }

        xen_pcibk_disconnect(pdev);

        /* N.B. This calls pcistub_put_pci_dev which does the FLR on all
         * of the PCIe devices. */
        xen_pcibk_release_devices(pdev);

        dev_set_drvdata(&pdev->xdev->dev, NULL);
        pdev->xdev = NULL;

        kfree(pdev);
}

static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref,
                             evtchn_port_t remote_evtchn)
{
        int err = 0;
        void *vaddr;

        dev_dbg(&pdev->xdev->dev,
                "Attaching to frontend resources - gnt_ref=%d evtchn=%u\n",
                gnt_ref, remote_evtchn);

        err = xenbus_map_ring_valloc(pdev->xdev, &gnt_ref, 1, &vaddr);
        if (err < 0) {
                xenbus_dev_fatal(pdev->xdev, err,
                                "Error mapping other domain page in ours.");
                goto out;
        }

        pdev->sh_info = vaddr;

        err = bind_interdomain_evtchn_to_irqhandler_lateeoi(
                pdev->xdev, remote_evtchn, xen_pcibk_handle_event,
                0, DRV_NAME, pdev);
        if (err < 0) {
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error binding event channel to IRQ");
                goto out;
        }
        pdev->evtchn_irq = err;
        err = 0;

        dev_dbg(&pdev->xdev->dev, "Attached!\n");
out:
        return err;
}

static int xen_pcibk_attach(struct xen_pcibk_device *pdev)
{
        int err = 0;
        int gnt_ref;
        evtchn_port_t remote_evtchn;
        char *magic = NULL;


        mutex_lock(&pdev->dev_lock);
        /* Make sure we only do this setup once */
        if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
            XenbusStateInitialised)
                goto out;

        /* Wait for frontend to state that it has published the configuration */
        if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->otherend) !=
            XenbusStateInitialised)
                goto out;

        dev_dbg(&pdev->xdev->dev, "Reading frontend config\n");

        err = xenbus_gather(XBT_NIL, pdev->xdev->otherend,
                            "pci-op-ref", "%u", &gnt_ref,
                            "event-channel", "%u", &remote_evtchn,
                            "magic", NULL, &magic, NULL);
        if (err) {
                /* If configuration didn't get read correctly, wait longer */
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error reading configuration from frontend");
                goto out;
        }

        if (magic == NULL || strcmp(magic, XEN_PCI_MAGIC) != 0) {
                xenbus_dev_fatal(pdev->xdev, -EFAULT,
                                 "version mismatch (%s/%s) with pcifront - "
                                 "halting " DRV_NAME,
                                 magic, XEN_PCI_MAGIC);
                err = -EFAULT;
                goto out;
        }

        err = xen_pcibk_do_attach(pdev, gnt_ref, remote_evtchn);
        if (err)
                goto out;

        dev_dbg(&pdev->xdev->dev, "Connecting...\n");

        err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);
        if (err)
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error switching to connected state!");

        dev_dbg(&pdev->xdev->dev, "Connected? %d\n", err);
out:
        mutex_unlock(&pdev->dev_lock);

        kfree(magic);

        return err;
}

static int xen_pcibk_publish_pci_dev(struct xen_pcibk_device *pdev,
                                   unsigned int domain, unsigned int bus,
                                   unsigned int devfn, unsigned int devid)
{
        int err;
        int len;
        char str[64];

        len = snprintf(str, sizeof(str), "vdev-%d", devid);
        if (unlikely(len >= (sizeof(str) - 1))) {
                err = -ENOMEM;
                goto out;
        }

        /* Note: The PV protocol uses %02x, don't change it */
        err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
                            "%04x:%02x:%02x.%02x", domain, bus,
                            PCI_SLOT(devfn), PCI_FUNC(devfn));

out:
        return err;
}

static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
                                 int domain, int bus, int slot, int func,
                                 int devid)
{
        struct pci_dev *dev;
        int err = 0;

        dev_dbg(&pdev->xdev->dev, "exporting dom %x bus %x slot %x func %x\n",
                domain, bus, slot, func);

        dev = pcistub_get_pci_dev_by_slot(pdev, domain, bus, slot, func);
        if (!dev) {
                err = -EINVAL;
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Couldn't locate PCI device "
                                 "(%04x:%02x:%02x.%d)! "
                                 "perhaps already in-use?",
                                 domain, bus, slot, func);
                goto out;
        }

        err = xen_pcibk_add_pci_dev(pdev, dev, devid,
                                    xen_pcibk_publish_pci_dev);
        if (err)
                goto out;

        dev_info(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
        if (xen_register_device_domain_owner(dev,
                                             pdev->xdev->otherend_id) != 0) {
                dev_err(&dev->dev, "Stealing ownership from dom%d.\n",
                        xen_find_device_domain_owner(dev));
                xen_unregister_device_domain_owner(dev);
                xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
        }

        /* TODO: It'd be nice to export a bridge and have all of its children
         * get exported with it. This may be best done in xend (which will
         * have to calculate resource usage anyway) but we probably want to
         * put something in here to ensure that if a bridge gets given to a
         * driver domain, that all devices under that bridge are not given
         * to other driver domains (as he who controls the bridge can disable
         * it and stop the other devices from working).
         */
out:
        return err;
}

static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
                                 int domain, int bus, int slot, int func)
{
        int err = 0;
        struct pci_dev *dev;

        dev_dbg(&pdev->xdev->dev, "removing dom %x bus %x slot %x func %x\n",
                domain, bus, slot, func);

        dev = xen_pcibk_get_pci_dev(pdev, domain, bus, PCI_DEVFN(slot, func));
        if (!dev) {
                err = -EINVAL;
                dev_dbg(&pdev->xdev->dev, "Couldn't locate PCI device "
                        "(%04x:%02x:%02x.%d)! not owned by this domain\n",
                        domain, bus, slot, func);
                goto out;
        }

        dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
        xen_unregister_device_domain_owner(dev);

        /* N.B. This ends up calling pcistub_put_pci_dev which ends up
         * doing the FLR. */
        xen_pcibk_release_pci_dev(pdev, dev, true /* use the lock. */);

out:
        return err;
}

static int xen_pcibk_publish_pci_root(struct xen_pcibk_device *pdev,
                                    unsigned int domain, unsigned int bus)
{
        unsigned int d, b;
        int i, root_num, len, err;
        char str[64];

        dev_dbg(&pdev->xdev->dev, "Publishing pci roots\n");

        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                           "root_num", "%d", &root_num);
        if (err == 0 || err == -ENOENT)
                root_num = 0;
        else if (err < 0)
                goto out;

        /* Verify that we haven't already published this pci root */
        for (i = 0; i < root_num; i++) {
                len = snprintf(str, sizeof(str), "root-%d", i);
                if (unlikely(len >= (sizeof(str) - 1))) {
                        err = -ENOMEM;
                        goto out;
                }

                err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                                   str, "%x:%x", &d, &b);
                if (err < 0)
                        goto out;
                if (err != 2) {
                        err = -EINVAL;
                        goto out;
                }

                if (d == domain && b == bus) {
                        err = 0;
                        goto out;
                }
        }

        len = snprintf(str, sizeof(str), "root-%d", root_num);
        if (unlikely(len >= (sizeof(str) - 1))) {
                err = -ENOMEM;
                goto out;
        }

        dev_dbg(&pdev->xdev->dev, "writing root %d at %04x:%02x\n",
                root_num, domain, bus);

        err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, str,
                            "%04x:%02x", domain, bus);
        if (err)
                goto out;

        err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
                            "root_num", "%d", (root_num + 1));

out:
        return err;
}

static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev,
                                 enum xenbus_state state)
{
        int err = 0;
        int num_devs;
        int domain, bus, slot, func;
        unsigned int substate;
        int i, len;
        char state_str[64];
        char dev_str[64];


        dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");

        mutex_lock(&pdev->dev_lock);
        if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) != state)
                goto out;

        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
                           &num_devs);
        if (err != 1) {
                if (err >= 0)
                        err = -EINVAL;
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error reading number of devices");
                goto out;
        }

        for (i = 0; i < num_devs; i++) {
                len = snprintf(state_str, sizeof(state_str), "state-%d", i);
                if (unlikely(len >= (sizeof(state_str) - 1))) {
                        err = -ENOMEM;
                        xenbus_dev_fatal(pdev->xdev, err,
                                         "String overflow while reading "
                                         "configuration");
                        goto out;
                }
                substate = xenbus_read_unsigned(pdev->xdev->nodename, state_str,
                                                XenbusStateUnknown);

                switch (substate) {
                case XenbusStateInitialising:
                        dev_dbg(&pdev->xdev->dev, "Attaching dev-%d ...\n", i);

                        len = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
                        if (unlikely(len >= (sizeof(dev_str) - 1))) {
                                err = -ENOMEM;
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "String overflow while "
                                                 "reading configuration");
                                goto out;
                        }
                        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                                           dev_str, "%x:%x:%x.%x",
                                           &domain, &bus, &slot, &func);
                        if (err < 0) {
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error reading device "
                                                 "configuration");
                                goto out;
                        }
                        if (err != 4) {
                                err = -EINVAL;
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error parsing pci device "
                                                 "configuration");
                                goto out;
                        }

                        err = xen_pcibk_export_device(pdev, domain, bus, slot,
                                                    func, i);
                        if (err)
                                goto out;

                        /* Publish pci roots. */
                        err = xen_pcibk_publish_pci_roots(pdev,
                                                xen_pcibk_publish_pci_root);
                        if (err) {
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error while publish PCI root"
                                                 "buses for frontend");
                                goto out;
                        }

                        err = xenbus_printf(XBT_NIL, pdev->xdev->nodename,
                                            state_str, "%d",
                                            XenbusStateInitialised);
                        if (err) {
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error switching substate of "
                                                 "dev-%d\n", i);
                                goto out;
                        }
                        break;

                case XenbusStateClosing:
                        dev_dbg(&pdev->xdev->dev, "Detaching dev-%d ...\n", i);

                        len = snprintf(dev_str, sizeof(dev_str), "vdev-%d", i);
                        if (unlikely(len >= (sizeof(dev_str) - 1))) {
                                err = -ENOMEM;
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "String overflow while "
                                                 "reading configuration");
                                goto out;
                        }
                        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename,
                                           dev_str, "%x:%x:%x.%x",
                                           &domain, &bus, &slot, &func);
                        if (err < 0) {
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error reading device "
                                                 "configuration");
                                goto out;
                        }
                        if (err != 4) {
                                err = -EINVAL;
                                xenbus_dev_fatal(pdev->xdev, err,
                                                 "Error parsing pci device "
                                                 "configuration");
                                goto out;
                        }

                        err = xen_pcibk_remove_device(pdev, domain, bus, slot,
                                                    func);
                        if (err)
                                goto out;

                        /* TODO: If at some point we implement support for pci
                         * root hot-remove on pcifront side, we'll need to
                         * remove unnecessary xenstore nodes of pci roots here.
                         */

                        break;

                default:
                        break;
                }
        }

        if (state != XenbusStateReconfiguring)
                /* Make sure we only reconfigure once. */
                goto out;

        err = xenbus_switch_state(pdev->xdev, XenbusStateReconfigured);
        if (err) {
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error switching to reconfigured state!");
                goto out;
        }

out:
        mutex_unlock(&pdev->dev_lock);
        return 0;
}

static void xen_pcibk_frontend_changed(struct xenbus_device *xdev,
                                     enum xenbus_state fe_state)
{
        struct xen_pcibk_device *pdev = dev_get_drvdata(&xdev->dev);

        dev_dbg(&xdev->dev, "fe state changed %d\n", fe_state);

        switch (fe_state) {
        case XenbusStateInitialised:
                xen_pcibk_attach(pdev);
                break;

        case XenbusStateReconfiguring:
                xen_pcibk_reconfigure(pdev, XenbusStateReconfiguring);
                break;

        case XenbusStateConnected:
                /* pcifront switched its state from reconfiguring to connected.
                 * Then switch to connected state.
                 */
                xenbus_switch_state(xdev, XenbusStateConnected);
                break;

        case XenbusStateClosing:
                xen_pcibk_disconnect(pdev);
                xenbus_switch_state(xdev, XenbusStateClosing);
                break;

        case XenbusStateClosed:
                xen_pcibk_disconnect(pdev);
                xenbus_switch_state(xdev, XenbusStateClosed);
                if (xenbus_dev_is_online(xdev))
                        break;
                fallthrough;    /* if not online */
        case XenbusStateUnknown:
                dev_dbg(&xdev->dev, "frontend is gone! unregister device\n");
                device_unregister(&xdev->dev);
                break;

        default:
                break;
        }
}

static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev)
{
        /* Get configuration from xend (if available now) */
        int domain, bus, slot, func;
        int err = 0;
        int i, num_devs;
        char dev_str[64];
        char state_str[64];

        mutex_lock(&pdev->dev_lock);
        /* It's possible we could get the call to setup twice, so make sure
         * we're not already connected.
         */
        if (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename) !=
            XenbusStateInitWait)
                goto out;

        dev_dbg(&pdev->xdev->dev, "getting be setup\n");

        err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, "num_devs", "%d",
                           &num_devs);
        if (err != 1) {
                if (err >= 0)
                        err = -EINVAL;
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error reading number of devices");
                goto out;
        }

        for (i = 0; i < num_devs; i++) {
                int l = snprintf(dev_str, sizeof(dev_str), "dev-%d", i);
                if (unlikely(l >= (sizeof(dev_str) - 1))) {
                        err = -ENOMEM;
                        xenbus_dev_fatal(pdev->xdev, err,
                                         "String overflow while reading "
                                         "configuration");
                        goto out;
                }

                err = xenbus_scanf(XBT_NIL, pdev->xdev->nodename, dev_str,
                                   "%x:%x:%x.%x", &domain, &bus, &slot, &func);
                if (err < 0) {
                        xenbus_dev_fatal(pdev->xdev, err,
                                         "Error reading device configuration");
                        goto out;
                }
                if (err != 4) {
                        err = -EINVAL;
                        xenbus_dev_fatal(pdev->xdev, err,
                                         "Error parsing pci device "
                                         "configuration");
                        goto out;
                }

                err = xen_pcibk_export_device(pdev, domain, bus, slot, func, i);
                if (err)
                        goto out;

                /* Switch substate of this device. */
                l = snprintf(state_str, sizeof(state_str), "state-%d", i);
                if (unlikely(l >= (sizeof(state_str) - 1))) {
                        err = -ENOMEM;
                        xenbus_dev_fatal(pdev->xdev, err,
                                         "String overflow while reading "
                                         "configuration");
                        goto out;
                }
                err = xenbus_printf(XBT_NIL, pdev->xdev->nodename, state_str,
                                    "%d", XenbusStateInitialised);
                if (err) {
                        xenbus_dev_fatal(pdev->xdev, err, "Error switching "
                                         "substate of dev-%d\n", i);
                        goto out;
                }
        }

        err = xen_pcibk_publish_pci_roots(pdev, xen_pcibk_publish_pci_root);
        if (err) {
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error while publish PCI root buses "
                                 "for frontend");
                goto out;
        }

        err = xenbus_switch_state(pdev->xdev, XenbusStateInitialised);
        if (err)
                xenbus_dev_fatal(pdev->xdev, err,
                                 "Error switching to initialised state!");

out:
        mutex_unlock(&pdev->dev_lock);
        if (!err)
                /* see if pcifront is already configured (if not, we'll wait) */
                xen_pcibk_attach(pdev);
        return err;
}

static void xen_pcibk_be_watch(struct xenbus_watch *watch,
                               const char *path, const char *token)
{
        struct xen_pcibk_device *pdev =
            container_of(watch, struct xen_pcibk_device, be_watch);

        switch (xenbus_read_driver_state(pdev->xdev, pdev->xdev->nodename)) {
        case XenbusStateInitWait:
                xen_pcibk_setup_backend(pdev);
                break;

        case XenbusStateInitialised:
                /*
                 * We typically move to Initialised when the first device was
                 * added. Hence subsequent devices getting added may need
                 * reconfiguring.
                 */
                xen_pcibk_reconfigure(pdev, XenbusStateInitialised);
                break;

        default:
                break;
        }
}

static int xen_pcibk_xenbus_probe(struct xenbus_device *dev,
                                const struct xenbus_device_id *id)
{
        int err = 0;
        struct xen_pcibk_device *pdev = alloc_pdev(dev);

        if (pdev == NULL) {
                err = -ENOMEM;
                xenbus_dev_fatal(dev, err,
                                 "Error allocating xen_pcibk_device struct");
                goto out;
        }

        /* wait for xend to configure us */
        err = xenbus_switch_state(dev, XenbusStateInitWait);
        if (err)
                goto out;

        /* watch the backend node for backend configuration information */
        err = xenbus_watch_path(dev, dev->nodename, &pdev->be_watch,
                                NULL, xen_pcibk_be_watch);
        if (err)
                goto out;

        pdev->be_watching = 1;

        /* We need to force a call to our callback here in case
         * xend already configured us!
         */
        xen_pcibk_be_watch(&pdev->be_watch, NULL, NULL);

out:
        return err;
}

static void xen_pcibk_xenbus_remove(struct xenbus_device *dev)
{
        struct xen_pcibk_device *pdev = dev_get_drvdata(&dev->dev);

        if (pdev != NULL)
                free_pdev(pdev);
}

static const struct xenbus_device_id xen_pcibk_ids[] = {
        {"pci"},
        {""},
};

static struct xenbus_driver xen_pcibk_driver = {
        .name                   = DRV_NAME,
        .ids                    = xen_pcibk_ids,
        .probe                  = xen_pcibk_xenbus_probe,
        .remove                 = xen_pcibk_xenbus_remove,
        .otherend_changed       = xen_pcibk_frontend_changed,
};

const struct xen_pcibk_backend *__read_mostly xen_pcibk_backend;

int __init xen_pcibk_xenbus_register(void)
{
        if (!xen_pcibk_pv_support())
                return 0;

        xen_pcibk_backend = &xen_pcibk_vpci_backend;
        if (passthrough)
                xen_pcibk_backend = &xen_pcibk_passthrough_backend;
        pr_info("backend is %s\n", xen_pcibk_backend->name);
        return xenbus_register_backend(&xen_pcibk_driver);
}

void __exit xen_pcibk_xenbus_unregister(void)
{
        if (xen_pcibk_pv_support())
                xenbus_unregister_driver(&xen_pcibk_driver);
}