xen-pcifront.c

Go to the documentation of this file.

/*
 * Xen PCI Frontend.
 *
 *   Author: Ryan Wilson <[email protected]>
 */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <xen/xenbus.h>
#include <xen/events.h>
#include <xen/grant_table.h>
#include <xen/page.h>
#include <linux/spinlock.h>
#include <linux/pci.h>
#include <linux/msi.h>
#include <xen/interface/io/pciif.h>
#include <asm/xen/pci.h>
#include <linux/interrupt.h>
#include <linux/atomic.h>
#include <linux/workqueue.h>
#include <linux/bitops.h>
#include <linux/time.h>

#include <asm/xen/swiotlb-xen.h>
#define INVALID_GRANT_REF (0)
#define INVALID_EVTCHN    (-1)

struct pci_bus_entry {
    struct list_head list;
    struct pci_bus *bus;
};

#define _PDEVB_op_active        (0)
#define PDEVB_op_active         (1 << (_PDEVB_op_active))

struct pcifront_device {
    struct xenbus_device *xdev;
    struct list_head root_buses;

    int evtchn;
    int gnt_ref;

    int irq;

    /* Lock this when doing any operations in sh_info */
    spinlock_t sh_info_lock;
    struct xen_pci_sharedinfo *sh_info;
    struct work_struct op_work;
    unsigned long flags;

};

struct pcifront_sd {
    int domain;
    struct pcifront_device *pdev;
};

static inline struct pcifront_device *
pcifront_get_pdev(struct pcifront_sd *sd)
{
    return sd->pdev;
}

static inline void pcifront_init_sd(struct pcifront_sd *sd,
                    unsigned int domain, unsigned int bus,
                    struct pcifront_device *pdev)
{
    sd->domain = domain;
    sd->pdev = pdev;
}

static DEFINE_SPINLOCK(pcifront_dev_lock);
static struct pcifront_device *pcifront_dev;

static int verbose_request;
module_param(verbose_request, int, 0644);

static int errno_to_pcibios_err(int errno)
{
    switch (errno) {
    case XEN_PCI_ERR_success:
        return PCIBIOS_SUCCESSFUL;

    case XEN_PCI_ERR_dev_not_found:
        return PCIBIOS_DEVICE_NOT_FOUND;

    case XEN_PCI_ERR_invalid_offset:
    case XEN_PCI_ERR_op_failed:
        return PCIBIOS_BAD_REGISTER_NUMBER;

    case XEN_PCI_ERR_not_implemented:
        return PCIBIOS_FUNC_NOT_SUPPORTED;

    case XEN_PCI_ERR_access_denied:
        return PCIBIOS_SET_FAILED;
    }
    return errno;
}

static inline void schedule_pcifront_aer_op(struct pcifront_device *pdev)
{
    if (test_bit(_XEN_PCIB_active, (unsigned long *)&pdev->sh_info->flags)
        && !test_and_set_bit(_PDEVB_op_active, &pdev->flags)) {
        dev_dbg(&pdev->xdev->dev, "schedule aer frontend job\n");
        schedule_work(&pdev->op_work);
    }
}

static int do_pci_op(struct pcifront_device *pdev, struct xen_pci_op *op)
{
    int err = 0;
    struct xen_pci_op *active_op = &pdev->sh_info->op;
    unsigned long irq_flags;
    evtchn_port_t port = pdev->evtchn;
    unsigned irq = pdev->irq;
    s64 ns, ns_timeout;
    struct timeval tv;

    spin_lock_irqsave(&pdev->sh_info_lock, irq_flags);

    memcpy(active_op, op, sizeof(struct xen_pci_op));

    /* Go */
    wmb();
    set_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
    notify_remote_via_evtchn(port);

    /*
     * We set a poll timeout of 3 seconds but give up on return after
     * 2 seconds. It is better to time out too late rather than too early
     * (in the latter case we end up continually re-executing poll() with a
     * timeout in the past). 1s difference gives plenty of slack for error.
     */
    do_gettimeofday(&tv);
    ns_timeout = timeval_to_ns(&tv) + 2 * (s64)NSEC_PER_SEC;

    xen_clear_irq_pending(irq);

    while (test_bit(_XEN_PCIF_active,
            (unsigned long *)&pdev->sh_info->flags)) {
        xen_poll_irq_timeout(irq, jiffies + 3*HZ);
        xen_clear_irq_pending(irq);
        do_gettimeofday(&tv);
        ns = timeval_to_ns(&tv);
        if (ns > ns_timeout) {
            dev_err(&pdev->xdev->dev,
                "pciback not responding!!!\n");
            clear_bit(_XEN_PCIF_active,
                  (unsigned long *)&pdev->sh_info->flags);
            err = XEN_PCI_ERR_dev_not_found;
            goto out;
        }
    }

    /*
    * We might lose backend service request since we
    * reuse same evtchn with pci_conf backend response. So re-schedule
    * aer pcifront service.
    */
    if (test_bit(_XEN_PCIB_active,
            (unsigned long *)&pdev->sh_info->flags)) {
        dev_err(&pdev->xdev->dev,
            "schedule aer pcifront service\n");
        schedule_pcifront_aer_op(pdev);
    }

    memcpy(op, active_op, sizeof(struct xen_pci_op));

    err = op->err;
out:
    spin_unlock_irqrestore(&pdev->sh_info_lock, irq_flags);
    return err;
}

/* Access to this function is spinlocked in drivers/pci/access.c */
static int pcifront_bus_read(struct pci_bus *bus, unsigned int devfn,
                 int where, int size, u32 *val)
{
    int err = 0;
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_conf_read,
        .domain = pci_domain_nr(bus),
        .bus    = bus->number,
        .devfn  = devfn,
        .offset = where,
        .size   = size,
    };
    struct pcifront_sd *sd = bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);

    if (verbose_request)
        dev_info(&pdev->xdev->dev,
             "read dev=%04x:%02x:%02x.%d - offset %x size %d\n",
             pci_domain_nr(bus), bus->number, PCI_SLOT(devfn),
             PCI_FUNC(devfn), where, size);

    err = do_pci_op(pdev, &op);

    if (likely(!err)) {
        if (verbose_request)
            dev_info(&pdev->xdev->dev, "read got back value %x\n",
                 op.value);

        *val = op.value;
    } else if (err == -ENODEV) {
        /* No device here, pretend that it just returned 0 */
        err = 0;
        *val = 0;
    }

    return errno_to_pcibios_err(err);
}

/* Access to this function is spinlocked in drivers/pci/access.c */
static int pcifront_bus_write(struct pci_bus *bus, unsigned int devfn,
                  int where, int size, u32 val)
{
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_conf_write,
        .domain = pci_domain_nr(bus),
        .bus    = bus->number,
        .devfn  = devfn,
        .offset = where,
        .size   = size,
        .value  = val,
    };
    struct pcifront_sd *sd = bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);

    if (verbose_request)
        dev_info(&pdev->xdev->dev,
             "write dev=%04x:%02x:%02x.%d - "
             "offset %x size %d val %x\n",
             pci_domain_nr(bus), bus->number,
             PCI_SLOT(devfn), PCI_FUNC(devfn), where, size, val);

    return errno_to_pcibios_err(do_pci_op(pdev, &op));
}

static struct pci_ops pcifront_bus_ops = {
    .read = pcifront_bus_read,
    .write = pcifront_bus_write,
};

#ifdef CONFIG_PCI_MSI
static int pci_frontend_enable_msix(struct pci_dev *dev,
                    int vector[], int nvec)
{
    int err;
    int i;
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_enable_msix,
        .domain = pci_domain_nr(dev->bus),
        .bus = dev->bus->number,
        .devfn = dev->devfn,
        .value = nvec,
    };
    struct pcifront_sd *sd = dev->bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);
    struct msi_desc *entry;

    if (nvec > SH_INFO_MAX_VEC) {
        dev_err(&dev->dev, "too much vector for pci frontend: %x."
                   " Increase SH_INFO_MAX_VEC.\n", nvec);
        return -EINVAL;
    }

    i = 0;
    list_for_each_entry(entry, &dev->msi_list, list) {
        op.msix_entries[i].entry = entry->msi_attrib.entry_nr;
        /* Vector is useless at this point. */
        op.msix_entries[i].vector = -1;
        i++;
    }

    err = do_pci_op(pdev, &op);

    if (likely(!err)) {
        if (likely(!op.value)) {
            /* we get the result */
            for (i = 0; i < nvec; i++) {
                if (op.msix_entries[i].vector <= 0) {
                    dev_warn(&dev->dev, "MSI-X entry %d is invalid: %d!\n",
                        i, op.msix_entries[i].vector);
                    err = -EINVAL;
                    vector[i] = -1;
                    continue;
                }
                vector[i] = op.msix_entries[i].vector;
            }
        } else {
            printk(KERN_DEBUG "enable msix get value %x\n",
                op.value);
            err = op.value;
        }
    } else {
        dev_err(&dev->dev, "enable msix get err %x\n", err);
    }
    return err;
}

static void pci_frontend_disable_msix(struct pci_dev *dev)
{
    int err;
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_disable_msix,
        .domain = pci_domain_nr(dev->bus),
        .bus = dev->bus->number,
        .devfn = dev->devfn,
    };
    struct pcifront_sd *sd = dev->bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);

    err = do_pci_op(pdev, &op);

    /* What should do for error ? */
    if (err)
        dev_err(&dev->dev, "pci_disable_msix get err %x\n", err);
}

static int pci_frontend_enable_msi(struct pci_dev *dev, int vector[])
{
    int err;
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_enable_msi,
        .domain = pci_domain_nr(dev->bus),
        .bus = dev->bus->number,
        .devfn = dev->devfn,
    };
    struct pcifront_sd *sd = dev->bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);

    err = do_pci_op(pdev, &op);
    if (likely(!err)) {
        vector[0] = op.value;
        if (op.value <= 0) {
            dev_warn(&dev->dev, "MSI entry is invalid: %d!\n",
                op.value);
            err = -EINVAL;
            vector[0] = -1;
        }
    } else {
        dev_err(&dev->dev, "pci frontend enable msi failed for dev "
                    "%x:%x\n", op.bus, op.devfn);
        err = -EINVAL;
    }
    return err;
}

static void pci_frontend_disable_msi(struct pci_dev *dev)
{
    int err;
    struct xen_pci_op op = {
        .cmd    = XEN_PCI_OP_disable_msi,
        .domain = pci_domain_nr(dev->bus),
        .bus = dev->bus->number,
        .devfn = dev->devfn,
    };
    struct pcifront_sd *sd = dev->bus->sysdata;
    struct pcifront_device *pdev = pcifront_get_pdev(sd);

    err = do_pci_op(pdev, &op);
    if (err == XEN_PCI_ERR_dev_not_found) {
        /* XXX No response from backend, what shall we do? */
        printk(KERN_DEBUG "get no response from backend for disable MSI\n");
        return;
    }
    if (err)
        /* how can pciback notify us fail? */
        printk(KERN_DEBUG "get fake response frombackend\n");
}

static struct xen_pci_frontend_ops pci_frontend_ops = {
    .enable_msi = pci_frontend_enable_msi,
    .disable_msi = pci_frontend_disable_msi,
    .enable_msix = pci_frontend_enable_msix,
    .disable_msix = pci_frontend_disable_msix,
};

static void pci_frontend_registrar(int enable)
{
    if (enable)
        xen_pci_frontend = &pci_frontend_ops;
    else
        xen_pci_frontend = NULL;
};
#else
static inline void pci_frontend_registrar(int enable) { };
#endif /* CONFIG_PCI_MSI */

/* Claim resources for the PCI frontend as-is, backend won't allow changes */
static int pcifront_claim_resource(struct pci_dev *dev, void *data)
{
    struct pcifront_device *pdev = data;
    int i;
    struct resource *r;

    for (i = 0; i < PCI_NUM_RESOURCES; i++) {
        r = &dev->resource[i];

        if (!r->parent && r->start && r->flags) {
            dev_info(&pdev->xdev->dev, "claiming resource %s/%d\n",
                pci_name(dev), i);
            if (pci_claim_resource(dev, i)) {
                dev_err(&pdev->xdev->dev, "Could not claim resource %s/%d! "
                    "Device offline. Try using e820_host=1 in the guest config.\n",
                    pci_name(dev), i);
            }
        }
    }

    return 0;
}

static int __devinit pcifront_scan_bus(struct pcifront_device *pdev,
                unsigned int domain, unsigned int bus,
                struct pci_bus *b)
{
    struct pci_dev *d;
    unsigned int devfn;

    /* Scan the bus for functions and add.
     * We omit handling of PCI bridge attachment because pciback prevents
     * bridges from being exported.
     */
    for (devfn = 0; devfn < 0x100; devfn++) {
        d = pci_get_slot(b, devfn);
        if (d) {
            /* Device is already known. */
            pci_dev_put(d);
            continue;
        }

        d = pci_scan_single_device(b, devfn);
        if (d)
            dev_info(&pdev->xdev->dev, "New device on "
                 "%04x:%02x:%02x.%d found.\n", domain, bus,
                 PCI_SLOT(devfn), PCI_FUNC(devfn));
    }

    return 0;
}

static int __devinit pcifront_scan_root(struct pcifront_device *pdev,
                 unsigned int domain, unsigned int bus)
{
    struct pci_bus *b;
    struct pcifront_sd *sd = NULL;
    struct pci_bus_entry *bus_entry = NULL;
    int err = 0;

#ifndef CONFIG_PCI_DOMAINS
    if (domain != 0) {
        dev_err(&pdev->xdev->dev,
            "PCI Root in non-zero PCI Domain! domain=%d\n", domain);
        dev_err(&pdev->xdev->dev,
            "Please compile with CONFIG_PCI_DOMAINS\n");
        err = -EINVAL;
        goto err_out;
    }
#endif

    dev_info(&pdev->xdev->dev, "Creating PCI Frontend Bus %04x:%02x\n",
         domain, bus);

    bus_entry = kmalloc(sizeof(*bus_entry), GFP_KERNEL);
    sd = kmalloc(sizeof(*sd), GFP_KERNEL);
    if (!bus_entry || !sd) {
        err = -ENOMEM;
        goto err_out;
    }
    pcifront_init_sd(sd, domain, bus, pdev);

    b = pci_scan_bus_parented(&pdev->xdev->dev, bus,
                  &pcifront_bus_ops, sd);
    if (!b) {
        dev_err(&pdev->xdev->dev,
            "Error creating PCI Frontend Bus!\n");
        err = -ENOMEM;
        goto err_out;
    }

    bus_entry->bus = b;

    list_add(&bus_entry->list, &pdev->root_buses);

    /* pci_scan_bus_parented skips devices which do not have a have
    * devfn==0. The pcifront_scan_bus enumerates all devfn. */
    err = pcifront_scan_bus(pdev, domain, bus, b);

    /* Claim resources before going "live" with our devices */
    pci_walk_bus(b, pcifront_claim_resource, pdev);

    /* Create SysFS and notify udev of the devices. Aka: "going live" */
    pci_bus_add_devices(b);

    return err;

err_out:
    kfree(bus_entry);
    kfree(sd);

    return err;
}

static int __devinit pcifront_rescan_root(struct pcifront_device *pdev,
                   unsigned int domain, unsigned int bus)
{
    int err;
    struct pci_bus *b;

#ifndef CONFIG_PCI_DOMAINS
    if (domain != 0) {
        dev_err(&pdev->xdev->dev,
            "PCI Root in non-zero PCI Domain! domain=%d\n", domain);
        dev_err(&pdev->xdev->dev,
            "Please compile with CONFIG_PCI_DOMAINS\n");
        return -EINVAL;
    }
#endif

    dev_info(&pdev->xdev->dev, "Rescanning PCI Frontend Bus %04x:%02x\n",
         domain, bus);

    b = pci_find_bus(domain, bus);
    if (!b)
        /* If the bus is unknown, create it. */
        return pcifront_scan_root(pdev, domain, bus);

    err = pcifront_scan_bus(pdev, domain, bus, b);

    /* Claim resources before going "live" with our devices */
    pci_walk_bus(b, pcifront_claim_resource, pdev);

    /* Create SysFS and notify udev of the devices. Aka: "going live" */
    pci_bus_add_devices(b);

    return err;
}

static void free_root_bus_devs(struct pci_bus *bus)
{
    struct pci_dev *dev;

    while (!list_empty(&bus->devices)) {
        dev = container_of(bus->devices.next, struct pci_dev,
                   bus_list);
        dev_dbg(&dev->dev, "removing device\n");
        pci_stop_and_remove_bus_device(dev);
    }
}

static void pcifront_free_roots(struct pcifront_device *pdev)
{
    struct pci_bus_entry *bus_entry, *t;

    dev_dbg(&pdev->xdev->dev, "cleaning up root buses\n");

    list_for_each_entry_safe(bus_entry, t, &pdev->root_buses, list) {
        list_del(&bus_entry->list);

        free_root_bus_devs(bus_entry->bus);

        kfree(bus_entry->bus->sysdata);

        device_unregister(bus_entry->bus->bridge);
        pci_remove_bus(bus_entry->bus);

        kfree(bus_entry);
    }
}

static pci_ers_result_t pcifront_common_process(int cmd,
                        struct pcifront_device *pdev,
                        pci_channel_state_t state)
{
    pci_ers_result_t result;
    struct pci_driver *pdrv;
    int bus = pdev->sh_info->aer_op.bus;
    int devfn = pdev->sh_info->aer_op.devfn;
    struct pci_dev *pcidev;
    int flag = 0;

    dev_dbg(&pdev->xdev->dev,
        "pcifront AER process: cmd %x (bus:%x, devfn%x)",
        cmd, bus, devfn);
    result = PCI_ERS_RESULT_NONE;

    pcidev = pci_get_bus_and_slot(bus, devfn);
    if (!pcidev || !pcidev->driver) {
        dev_err(&pdev->xdev->dev, "device or AER driver is NULL\n");
        if (pcidev)
            pci_dev_put(pcidev);
        return result;
    }
    pdrv = pcidev->driver;

    if (pdrv) {
        if (pdrv->err_handler && pdrv->err_handler->error_detected) {
            dev_dbg(&pcidev->dev,
                "trying to call AER service\n");
            if (pcidev) {
                flag = 1;
                switch (cmd) {
                case XEN_PCI_OP_aer_detected:
                    result = pdrv->err_handler->
                         error_detected(pcidev, state);
                    break;
                case XEN_PCI_OP_aer_mmio:
                    result = pdrv->err_handler->
                         mmio_enabled(pcidev);
                    break;
                case XEN_PCI_OP_aer_slotreset:
                    result = pdrv->err_handler->
                         slot_reset(pcidev);
                    break;
                case XEN_PCI_OP_aer_resume:
                    pdrv->err_handler->resume(pcidev);
                    break;
                default:
                    dev_err(&pdev->xdev->dev,
                        "bad request in aer recovery "
                        "operation!\n");

                }
            }
        }
    }
    if (!flag)
        result = PCI_ERS_RESULT_NONE;

    return result;
}


static void pcifront_do_aer(struct work_struct *data)
{
    struct pcifront_device *pdev =
        container_of(data, struct pcifront_device, op_work);
    int cmd = pdev->sh_info->aer_op.cmd;
    pci_channel_state_t state =
        (pci_channel_state_t)pdev->sh_info->aer_op.err;

    /*If a pci_conf op is in progress,
        we have to wait until it is done before service aer op*/
    dev_dbg(&pdev->xdev->dev,
        "pcifront service aer bus %x devfn %x\n",
        pdev->sh_info->aer_op.bus, pdev->sh_info->aer_op.devfn);

    pdev->sh_info->aer_op.err = pcifront_common_process(cmd, pdev, state);

    /* Post the operation to the guest. */
    wmb();
    clear_bit(_XEN_PCIB_active, (unsigned long *)&pdev->sh_info->flags);
    notify_remote_via_evtchn(pdev->evtchn);

    /*in case of we lost an aer request in four lines time_window*/
    smp_mb__before_clear_bit();
    clear_bit(_PDEVB_op_active, &pdev->flags);
    smp_mb__after_clear_bit();

    schedule_pcifront_aer_op(pdev);

}

static irqreturn_t pcifront_handler_aer(int irq, void *dev)
{
    struct pcifront_device *pdev = dev;
    schedule_pcifront_aer_op(pdev);
    return IRQ_HANDLED;
}
static int pcifront_connect_and_init_dma(struct pcifront_device *pdev)
{
    int err = 0;

    spin_lock(&pcifront_dev_lock);

    if (!pcifront_dev) {
        dev_info(&pdev->xdev->dev, "Installing PCI frontend\n");
        pcifront_dev = pdev;
    } else {
        dev_err(&pdev->xdev->dev, "PCI frontend already installed!\n");
        err = -EEXIST;
    }
    spin_unlock(&pcifront_dev_lock);

    if (!err && !swiotlb_nr_tbl()) {
        err = pci_xen_swiotlb_init_late();
        if (err)
            dev_err(&pdev->xdev->dev, "Could not setup SWIOTLB!\n");
    }
    return err;
}

static void pcifront_disconnect(struct pcifront_device *pdev)
{
    spin_lock(&pcifront_dev_lock);

    if (pdev == pcifront_dev) {
        dev_info(&pdev->xdev->dev,
             "Disconnecting PCI Frontend Buses\n");
        pcifront_dev = NULL;
    }

    spin_unlock(&pcifront_dev_lock);
}
static struct pcifront_device *alloc_pdev(struct xenbus_device *xdev)
{
    struct pcifront_device *pdev;

    pdev = kzalloc(sizeof(struct pcifront_device), GFP_KERNEL);
    if (pdev == NULL)
        goto out;

    pdev->sh_info =
        (struct xen_pci_sharedinfo *)__get_free_page(GFP_KERNEL);
    if (pdev->sh_info == NULL) {
        kfree(pdev);
        pdev = NULL;
        goto out;
    }
    pdev->sh_info->flags = 0;

    /*Flag for registering PV AER handler*/
    set_bit(_XEN_PCIB_AERHANDLER, (void *)&pdev->sh_info->flags);

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

    INIT_LIST_HEAD(&pdev->root_buses);

    spin_lock_init(&pdev->sh_info_lock);

    pdev->evtchn = INVALID_EVTCHN;
    pdev->gnt_ref = INVALID_GRANT_REF;
    pdev->irq = -1;

    INIT_WORK(&pdev->op_work, pcifront_do_aer);

    dev_dbg(&xdev->dev, "Allocated pdev @ 0x%p pdev->sh_info @ 0x%p\n",
        pdev, pdev->sh_info);
out:
    return pdev;
}

static void free_pdev(struct pcifront_device *pdev)
{
    dev_dbg(&pdev->xdev->dev, "freeing pdev @ 0x%p\n", pdev);

    pcifront_free_roots(pdev);

    cancel_work_sync(&pdev->op_work);

    if (pdev->irq >= 0)
        unbind_from_irqhandler(pdev->irq, pdev);

    if (pdev->evtchn != INVALID_EVTCHN)
        xenbus_free_evtchn(pdev->xdev, pdev->evtchn);

    if (pdev->gnt_ref != INVALID_GRANT_REF)
        gnttab_end_foreign_access(pdev->gnt_ref, 0 /* r/w page */,
                      (unsigned long)pdev->sh_info);
    else
        free_page((unsigned long)pdev->sh_info);

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

    kfree(pdev);
}

static int pcifront_publish_info(struct pcifront_device *pdev)
{
    int err = 0;
    struct xenbus_transaction trans;

    err = xenbus_grant_ring(pdev->xdev, virt_to_mfn(pdev->sh_info));
    if (err < 0)
        goto out;

    pdev->gnt_ref = err;

    err = xenbus_alloc_evtchn(pdev->xdev, &pdev->evtchn);
    if (err)
        goto out;

    err = bind_evtchn_to_irqhandler(pdev->evtchn, pcifront_handler_aer,
        0, "pcifront", pdev);

    if (err < 0)
        return err;

    pdev->irq = err;

do_publish:
    err = xenbus_transaction_start(&trans);
    if (err) {
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error writing configuration for backend "
                 "(start transaction)");
        goto out;
    }

    err = xenbus_printf(trans, pdev->xdev->nodename,
                "pci-op-ref", "%u", pdev->gnt_ref);
    if (!err)
        err = xenbus_printf(trans, pdev->xdev->nodename,
                    "event-channel", "%u", pdev->evtchn);
    if (!err)
        err = xenbus_printf(trans, pdev->xdev->nodename,
                    "magic", XEN_PCI_MAGIC);

    if (err) {
        xenbus_transaction_end(trans, 1);
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error writing configuration for backend");
        goto out;
    } else {
        err = xenbus_transaction_end(trans, 0);
        if (err == -EAGAIN)
            goto do_publish;
        else if (err) {
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error completing transaction "
                     "for backend");
            goto out;
        }
    }

    xenbus_switch_state(pdev->xdev, XenbusStateInitialised);

    dev_dbg(&pdev->xdev->dev, "publishing successful!\n");

out:
    return err;
}

static int __devinit pcifront_try_connect(struct pcifront_device *pdev)
{
    int err = -EFAULT;
    int i, num_roots, len;
    char str[64];
    unsigned int domain, bus;


    /* Only connect once */
    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateInitialised)
        goto out;

    err = pcifront_connect_and_init_dma(pdev);
    if (err) {
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error setting up PCI Frontend");
        goto out;
    }

    err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend,
               "root_num", "%d", &num_roots);
    if (err == -ENOENT) {
        xenbus_dev_error(pdev->xdev, err,
                 "No PCI Roots found, trying 0000:00");
        err = pcifront_scan_root(pdev, 0, 0);
        num_roots = 0;
    } else if (err != 1) {
        if (err == 0)
            err = -EINVAL;
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error reading number of PCI roots");
        goto out;
    }

    for (i = 0; i < num_roots; 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->otherend, str,
                   "%x:%x", &domain, &bus);
        if (err != 2) {
            if (err >= 0)
                err = -EINVAL;
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error reading PCI root %d", i);
            goto out;
        }

        err = pcifront_scan_root(pdev, domain, bus);
        if (err) {
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error scanning PCI root %04x:%02x",
                     domain, bus);
            goto out;
        }
    }

    err = xenbus_switch_state(pdev->xdev, XenbusStateConnected);

out:
    return err;
}

static int pcifront_try_disconnect(struct pcifront_device *pdev)
{
    int err = 0;
    enum xenbus_state prev_state;


    prev_state = xenbus_read_driver_state(pdev->xdev->nodename);

    if (prev_state >= XenbusStateClosing)
        goto out;

    if (prev_state == XenbusStateConnected) {
        pcifront_free_roots(pdev);
        pcifront_disconnect(pdev);
    }

    err = xenbus_switch_state(pdev->xdev, XenbusStateClosed);

out:

    return err;
}

static int __devinit pcifront_attach_devices(struct pcifront_device *pdev)
{
    int err = -EFAULT;
    int i, num_roots, len;
    unsigned int domain, bus;
    char str[64];

    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateReconfiguring)
        goto out;

    err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend,
               "root_num", "%d", &num_roots);
    if (err == -ENOENT) {
        xenbus_dev_error(pdev->xdev, err,
                 "No PCI Roots found, trying 0000:00");
        err = pcifront_rescan_root(pdev, 0, 0);
        num_roots = 0;
    } else if (err != 1) {
        if (err == 0)
            err = -EINVAL;
        xenbus_dev_fatal(pdev->xdev, err,
                 "Error reading number of PCI roots");
        goto out;
    }

    for (i = 0; i < num_roots; 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->otherend, str,
                   "%x:%x", &domain, &bus);
        if (err != 2) {
            if (err >= 0)
                err = -EINVAL;
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error reading PCI root %d", i);
            goto out;
        }

        err = pcifront_rescan_root(pdev, domain, bus);
        if (err) {
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error scanning PCI root %04x:%02x",
                     domain, bus);
            goto out;
        }
    }

    xenbus_switch_state(pdev->xdev, XenbusStateConnected);

out:
    return err;
}

static int pcifront_detach_devices(struct pcifront_device *pdev)
{
    int err = 0;
    int i, num_devs;
    unsigned int domain, bus, slot, func;
    struct pci_dev *pci_dev;
    char str[64];

    if (xenbus_read_driver_state(pdev->xdev->nodename) !=
        XenbusStateConnected)
        goto out;

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

    /* Find devices being detached and remove them. */
    for (i = 0; i < num_devs; i++) {
        int l, state;
        l = snprintf(str, sizeof(str), "state-%d", i);
        if (unlikely(l >= (sizeof(str) - 1))) {
            err = -ENOMEM;
            goto out;
        }
        err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend, str, "%d",
                   &state);
        if (err != 1)
            state = XenbusStateUnknown;

        if (state != XenbusStateClosing)
            continue;

        /* Remove device. */
        l = snprintf(str, sizeof(str), "vdev-%d", i);
        if (unlikely(l >= (sizeof(str) - 1))) {
            err = -ENOMEM;
            goto out;
        }
        err = xenbus_scanf(XBT_NIL, pdev->xdev->otherend, str,
                   "%x:%x:%x.%x", &domain, &bus, &slot, &func);
        if (err != 4) {
            if (err >= 0)
                err = -EINVAL;
            xenbus_dev_fatal(pdev->xdev, err,
                     "Error reading PCI device %d", i);
            goto out;
        }

        pci_dev = pci_get_domain_bus_and_slot(domain, bus,
                PCI_DEVFN(slot, func));
        if (!pci_dev) {
            dev_dbg(&pdev->xdev->dev,
                "Cannot get PCI device %04x:%02x:%02x.%d\n",
                domain, bus, slot, func);
            continue;
        }
        pci_stop_and_remove_bus_device(pci_dev);
        pci_dev_put(pci_dev);

        dev_dbg(&pdev->xdev->dev,
            "PCI device %04x:%02x:%02x.%d removed.\n",
            domain, bus, slot, func);
    }

    err = xenbus_switch_state(pdev->xdev, XenbusStateReconfiguring);

out:
    return err;
}

static void __init_refok pcifront_backend_changed(struct xenbus_device *xdev,
                          enum xenbus_state be_state)
{
    struct pcifront_device *pdev = dev_get_drvdata(&xdev->dev);

    switch (be_state) {
    case XenbusStateUnknown:
    case XenbusStateInitialising:
    case XenbusStateInitWait:
    case XenbusStateInitialised:
    case XenbusStateClosed:
        break;

    case XenbusStateConnected:
        pcifront_try_connect(pdev);
        break;

    case XenbusStateClosing:
        dev_warn(&xdev->dev, "backend going away!\n");
        pcifront_try_disconnect(pdev);
        break;

    case XenbusStateReconfiguring:
        pcifront_detach_devices(pdev);
        break;

    case XenbusStateReconfigured:
        pcifront_attach_devices(pdev);
        break;
    }
}

static int pcifront_xenbus_probe(struct xenbus_device *xdev,
                 const struct xenbus_device_id *id)
{
    int err = 0;
    struct pcifront_device *pdev = alloc_pdev(xdev);

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

    err = pcifront_publish_info(pdev);
    if (err)
        free_pdev(pdev);

out:
    return err;
}

static int pcifront_xenbus_remove(struct xenbus_device *xdev)
{
    struct pcifront_device *pdev = dev_get_drvdata(&xdev->dev);
    if (pdev)
        free_pdev(pdev);

    return 0;
}

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

static DEFINE_XENBUS_DRIVER(xenpci, "pcifront",
    .probe          = pcifront_xenbus_probe,
    .remove         = pcifront_xenbus_remove,
    .otherend_changed   = pcifront_backend_changed,
);

static int __init pcifront_init(void)
{
    if (!xen_pv_domain() || xen_initial_domain())
        return -ENODEV;

    pci_frontend_registrar(1 /* enable */);

    return xenbus_register_frontend(&xenpci_driver);
}

static void __exit pcifront_cleanup(void)
{
    xenbus_unregister_driver(&xenpci_driver);
    pci_frontend_registrar(0 /* disable */);
}
module_init(pcifront_init);
module_exit(pcifront_cleanup);

MODULE_DESCRIPTION("Xen PCI passthrough frontend.");
MODULE_LICENSE("GPL");
MODULE_ALIAS("xen:pci");