text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Xen PCI Frontend
   *
   * Author: Ryan Wilson <hap9@epoch.ncsc.mil>
   */
  #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 <linux/ktime.h>
  #include <xen/platform_pci.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 {
  	struct pci_sysdata sd;
  	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)
  {
  	/* Because we do not expose that information via XenBus. */
  	sd->sd.node = first_online_node;
  	sd->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;
  
  	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.
  	 */
  	ns_timeout = ktime_get_ns() + 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);
  		ns = ktime_get_ns();
  		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) {
  		pci_err(dev, "too many vectors (0x%x) for PCI frontend:"
  				   " Increase SH_INFO_MAX_VEC\n", nvec);
  		return -EINVAL;
  	}
  
  	i = 0;
  	for_each_pci_msi_entry(entry, dev) {
  		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) {
  					pci_warn(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 {
  			pr_info("enable msix get value %x\n", op.value);
  			err = op.value;
  		}
  	} else {
  		pci_err(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)
  		pci_err(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) {
  			pci_warn(dev, "MSI entry is invalid: %d!\n",
  				op.value);
  			err = -EINVAL;
  			vector[0] = -1;
  		}
  	} else {
  		pci_err(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? */
  		pr_info("get no response from backend for disable MSI\n");
  		return;
  	}
  	if (err)
  		/* how can pciback notify us fail? */
  		pr_info("get fake response from backend\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 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 pcifront_scan_root(struct pcifront_device *pdev,
  				 unsigned int domain, unsigned int bus)
  {
  	struct pci_bus *b;
  	LIST_HEAD(resources);
  	struct pcifront_sd *sd = NULL;
  	struct pci_bus_entry *bus_entry = NULL;
  	int err = 0;
  	static struct resource busn_res = {
  		.start = 0,
  		.end = 255,
  		.flags = IORESOURCE_BUS,
  	};
  
  #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 = kzalloc(sizeof(*bus_entry), GFP_KERNEL);
  	sd = kzalloc(sizeof(*sd), GFP_KERNEL);
  	if (!bus_entry || !sd) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	pci_add_resource(&resources, &ioport_resource);
  	pci_add_resource(&resources, &iomem_resource);
  	pci_add_resource(&resources, &busn_res);
  	pcifront_init_sd(sd, domain, bus, pdev);
  
  	pci_lock_rescan_remove();
  
  	b = pci_scan_root_bus(&pdev->xdev->dev, bus,
  				  &pcifront_bus_ops, sd, &resources);
  	if (!b) {
  		dev_err(&pdev->xdev->dev,
  			"Error creating PCI Frontend Bus!\n");
  		err = -ENOMEM;
  		pci_unlock_rescan_remove();
  		pci_free_resource_list(&resources);
  		goto err_out;
  	}
  
  	bus_entry->bus = b;
  
  	list_add(&bus_entry->list, &pdev->root_buses);
  
  	/* pci_scan_root_bus skips devices which do not have a
  	* 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);
  
  	pci_unlock_rescan_remove();
  	return err;
  
  err_out:
  	kfree(bus_entry);
  	kfree(sd);
  
  	return err;
  }
  
  static int 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);
  		pci_dbg(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");
  
  	pci_lock_rescan_remove();
  	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);
  	}
  	pci_unlock_rescan_remove();
  }
  
  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;
  	int domain = pdev->sh_info->aer_op.domain;
  	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_domain_bus_and_slot(domain, bus, devfn);
  	if (!pcidev || !pcidev->driver) {
  		dev_err(&pdev->xdev->dev, "device or AER driver is NULL\n");
  		pci_dev_put(pcidev);
  		return result;
  	}
  	pdrv = pcidev->driver;
  
  	if (pdrv) {
  		if (pdrv->err_handler && pdrv->err_handler->error_detected) {
  			pci_dbg(pcidev, "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_atomic();
  	clear_bit(_PDEVB_op_active, &pdev->flags);
  	smp_mb__after_atomic();
  
  	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
  		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;
  	grant_ref_t gref;
  
  	err = xenbus_grant_ring(pdev->xdev, pdev->sh_info, 1, &gref);
  	if (err < 0)
  		goto out;
  
  	pdev->gnt_ref = gref;
  
  	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 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 && err != -EEXIST) {
  		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);
  		if (err) {
  			xenbus_dev_fatal(pdev->xdev, err,
  					 "Error scanning PCI root 0000:00");
  			goto out;
  		}
  		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 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);
  		if (err) {
  			xenbus_dev_fatal(pdev->xdev, err,
  					 "Error scanning PCI root 0000:00");
  			goto out;
  		}
  		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;
  		}
  		state = xenbus_read_unsigned(pdev->xdev->otherend, str,
  					     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_lock_rescan_remove();
  		pci_stop_and_remove_bus_device(pci_dev);
  		pci_dev_put(pci_dev);
  		pci_unlock_rescan_remove();
  
  		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 __ref 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:
  		break;
  
  	case XenbusStateConnected:
  		pcifront_try_connect(pdev);
  		break;
  
  	case XenbusStateClosed:
  		if (xdev->state == XenbusStateClosed)
  			break;
  		/* fall through - Missed the backend's CLOSING state. */
  	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 struct xenbus_driver xenpci_driver = {
  	.name			= "pcifront",
  	.ids			= xenpci_ids,
  	.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;
  
  	if (!xen_has_pv_devices())
  		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");
  