/*
   * PCI Backend Operations - respond to PCI requests from Frontend
   *
   *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
   */

  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/module.h>
  #include <linux/wait.h>
  #include <linux/bitops.h>
  #include <xen/events.h>
  #include <linux/sched.h>
  #include "pciback.h"
  
  int verbose_request;
  module_param(verbose_request, int, 0644);

  static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id);

  /* Ensure a device is has the fake IRQ handler "turned on/off" and is

   * ready to be exported. This MUST be run after xen_pcibk_reset_device

   * which does the actual PCI device enable/disable.
   */

  static void xen_pcibk_control_isr(struct pci_dev *dev, int reset)

  {

  	struct xen_pcibk_dev_data *dev_data;

  	int rc;
  	int enable = 0;
  
  	dev_data = pci_get_drvdata(dev);
  	if (!dev_data)
  		return;
  
  	/* We don't deal with bridges */
  	if (dev->hdr_type != PCI_HEADER_TYPE_NORMAL)
  		return;
  
  	if (reset) {
  		dev_data->enable_intx = 0;
  		dev_data->ack_intr = 0;
  	}
  	enable =  dev_data->enable_intx;
  
  	/* Asked to disable, but ISR isn't runnig */
  	if (!enable && !dev_data->isr_on)
  		return;
  
  	/* Squirrel away the IRQs in the dev_data. We need this
  	 * b/c when device transitions to MSI, the dev->irq is
  	 * overwritten with the MSI vector.
  	 */
  	if (enable)
  		dev_data->irq = dev->irq;

  	/*
  	 * SR-IOV devices in all use MSI-X and have no legacy
  	 * interrupts, so inhibit creating a fake IRQ handler for them.
  	 */
  	if (dev_data->irq == 0)
  		goto out;

  	dev_dbg(&dev->dev, "%s: #%d %s %s%s %s-> %s
  ",
  		dev_data->irq_name,
  		dev_data->irq,
  		pci_is_enabled(dev) ? "on" : "off",
  		dev->msi_enabled ? "MSI" : "",
  		dev->msix_enabled ? "MSI/X" : "",
  		dev_data->isr_on ? "enable" : "disable",
  		enable ? "enable" : "disable");
  
  	if (enable) {

  		/*
  		 * The MSI or MSI-X should not have an IRQ handler. Otherwise
  		 * if the guest terminates we BUG_ON in free_msi_irqs.
  		 */
  		if (dev->msi_enabled || dev->msix_enabled)
  			goto out;

  		rc = request_irq(dev_data->irq,

  				xen_pcibk_guest_interrupt, IRQF_SHARED,

  				dev_data->irq_name, dev);
  		if (rc) {
  			dev_err(&dev->dev, "%s: failed to install fake IRQ " \
  				"handler for IRQ %d! (rc:%d)
  ",
  				dev_data->irq_name, dev_data->irq, rc);
  			goto out;
  		}
  	} else {
  		free_irq(dev_data->irq, dev);
  		dev_data->irq = 0;
  	}
  	dev_data->isr_on = enable;
  	dev_data->ack_intr = enable;
  out:
  	dev_dbg(&dev->dev, "%s: #%d %s %s%s %s
  ",
  		dev_data->irq_name,
  		dev_data->irq,
  		pci_is_enabled(dev) ? "on" : "off",
  		dev->msi_enabled ? "MSI" : "",
  		dev->msix_enabled ? "MSI/X" : "",
  		enable ? (dev_data->isr_on ? "enabled" : "failed to enable") :
  			(dev_data->isr_on ? "failed to disable" : "disabled"));
  }

  /* Ensure a device is "turned off" and ready to be exported.

   * (Also see xen_pcibk_config_reset to ensure virtual configuration space is

   * ready to be re-exported)
   */

  void xen_pcibk_reset_device(struct pci_dev *dev)

  {
  	u16 cmd;

  	xen_pcibk_control_isr(dev, 1 /* reset device */);

  	/* Disable devices (but not bridges) */
  	if (dev->hdr_type == PCI_HEADER_TYPE_NORMAL) {

  #ifdef CONFIG_PCI_MSI
  		/* The guest could have been abruptly killed without
  		 * disabling MSI/MSI-X interrupts.*/
  		if (dev->msix_enabled)
  			pci_disable_msix(dev);
  		if (dev->msi_enabled)
  			pci_disable_msi(dev);
  #endif

  		if (pci_is_enabled(dev))
  			pci_disable_device(dev);

  
  		pci_write_config_word(dev, PCI_COMMAND, 0);
  
  		dev->is_busmaster = 0;
  	} else {
  		pci_read_config_word(dev, PCI_COMMAND, &cmd);
  		if (cmd & (PCI_COMMAND_INVALIDATE)) {
  			cmd &= ~(PCI_COMMAND_INVALIDATE);
  			pci_write_config_word(dev, PCI_COMMAND, cmd);
  
  			dev->is_busmaster = 0;
  		}
  	}
  }

  
  #ifdef CONFIG_PCI_MSI
  static
  int xen_pcibk_enable_msi(struct xen_pcibk_device *pdev,
  			 struct pci_dev *dev, struct xen_pci_op *op)
  {
  	struct xen_pcibk_dev_data *dev_data;

  	int status;
  
  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: enable MSI
  ", pci_name(dev));

  	if (dev->msi_enabled)
  		status = -EALREADY;
  	else if (dev->msix_enabled)
  		status = -ENXIO;
  	else
  		status = pci_enable_msi(dev);

  
  	if (status) {

  		pr_warn_ratelimited("%s: error enabling MSI for guest %u: err %d
  ",

  				    pci_name(dev), pdev->xdev->otherend_id,
  				    status);

  		op->value = 0;
  		return XEN_PCI_ERR_op_failed;
  	}
  
  	/* The value the guest needs is actually the IDT vector, not the
  	 * the local domain's IRQ number. */
  
  	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: MSI: %d
  ", pci_name(dev),
  			op->value);
  
  	dev_data = pci_get_drvdata(dev);
  	if (dev_data)
  		dev_data->ack_intr = 0;
  
  	return 0;
  }
  
  static
  int xen_pcibk_disable_msi(struct xen_pcibk_device *pdev,
  			  struct pci_dev *dev, struct xen_pci_op *op)
  {

  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: disable MSI
  ",
  		       pci_name(dev));

  	if (dev->msi_enabled) {
  		struct xen_pcibk_dev_data *dev_data;
  
  		pci_disable_msi(dev);
  
  		dev_data = pci_get_drvdata(dev);
  		if (dev_data)
  			dev_data->ack_intr = 1;
  	}

  	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: MSI: %d
  ", pci_name(dev),
  			op->value);

  	return 0;
  }
  
  static
  int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
  			  struct pci_dev *dev, struct xen_pci_op *op)
  {
  	struct xen_pcibk_dev_data *dev_data;
  	int i, result;
  	struct msix_entry *entries;

  	u16 cmd;

  
  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: enable MSI-X
  ",
  		       pci_name(dev));

  	if (op->value > SH_INFO_MAX_VEC)
  		return -EINVAL;

  	if (dev->msix_enabled)
  		return -EALREADY;

  	/*
  	 * PCI_COMMAND_MEMORY must be enabled, otherwise we may not be able
  	 * to access the BARs where the MSI-X entries reside.
  	 */
  	pci_read_config_word(dev, PCI_COMMAND, &cmd);
  	if (dev->msi_enabled || !(cmd & PCI_COMMAND_MEMORY))

  		return -ENXIO;

  	entries = kmalloc(op->value * sizeof(*entries), GFP_KERNEL);
  	if (entries == NULL)
  		return -ENOMEM;
  
  	for (i = 0; i < op->value; i++) {
  		entries[i].entry = op->msix_entries[i].entry;
  		entries[i].vector = op->msix_entries[i].vector;
  	}

  	result = pci_enable_msix_exact(dev, entries, op->value);

  	if (result == 0) {
  		for (i = 0; i < op->value; i++) {
  			op->msix_entries[i].entry = entries[i].entry;

  			if (entries[i].vector) {

  				op->msix_entries[i].vector =
  					xen_pirq_from_irq(entries[i].vector);
  				if (unlikely(verbose_request))
  					printk(KERN_DEBUG DRV_NAME ": %s: " \
  						"MSI-X[%d]: %d
  ",
  						pci_name(dev), i,
  						op->msix_entries[i].vector);

  			}

  		}

  	} else

  		pr_warn_ratelimited("%s: error enabling MSI-X for guest %u: err %d!
  ",

  				    pci_name(dev), pdev->xdev->otherend_id,
  				    result);

  	kfree(entries);
  
  	op->value = result;
  	dev_data = pci_get_drvdata(dev);
  	if (dev_data)
  		dev_data->ack_intr = 0;

  	return result > 0 ? 0 : result;

  }
  
  static
  int xen_pcibk_disable_msix(struct xen_pcibk_device *pdev,
  			   struct pci_dev *dev, struct xen_pci_op *op)
  {

  	if (unlikely(verbose_request))
  		printk(KERN_DEBUG DRV_NAME ": %s: disable MSI-X
  ",
  			pci_name(dev));

  	if (dev->msix_enabled) {
  		struct xen_pcibk_dev_data *dev_data;
  
  		pci_disable_msix(dev);
  
  		dev_data = pci_get_drvdata(dev);
  		if (dev_data)
  			dev_data->ack_intr = 1;
  	}

  	/*
  	 * SR-IOV devices (which don't have any legacy IRQ) have
  	 * an undefined IRQ value of zero.
  	 */
  	op->value = dev->irq ? xen_pirq_from_irq(dev->irq) : 0;
  	if (unlikely(verbose_request))

  		printk(KERN_DEBUG DRV_NAME ": %s: MSI-X: %d
  ",
  		       pci_name(dev), op->value);

  	return 0;
  }
  #endif

  /*
  * Now the same evtchn is used for both pcifront conf_read_write request
  * as well as pcie aer front end ack. We use a new work_queue to schedule

  * xen_pcibk conf_read_write service for avoiding confict with aer_core

  * do_recovery job which also use the system default work_queue
  */

  void xen_pcibk_test_and_schedule_op(struct xen_pcibk_device *pdev)

  {
  	/* Check that frontend is requesting an operation and that we are not
  	 * already processing a request */
  	if (test_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags)
  	    && !test_and_set_bit(_PDEVF_op_active, &pdev->flags)) {

  		queue_work(xen_pcibk_wq, &pdev->op_work);

  	}
  	/*_XEN_PCIB_active should have been cleared by pcifront. And also make

  	sure xen_pcibk is waiting for ack by checking _PCIB_op_pending*/

  	if (!test_bit(_XEN_PCIB_active, (unsigned long *)&pdev->sh_info->flags)
  	    && test_bit(_PCIB_op_pending, &pdev->flags)) {

  		wake_up(&xen_pcibk_aer_wait_queue);

  	}
  }
  
  /* Performing the configuration space reads/writes must not be done in atomic
   * context because some of the pci_* functions can sleep (mostly due to ACPI
   * use of semaphores). This function is intended to be called from a work

   * queue in process context taking a struct xen_pcibk_device as a parameter */

  void xen_pcibk_do_op(struct work_struct *data)

  {

  	struct xen_pcibk_device *pdev =
  		container_of(data, struct xen_pcibk_device, op_work);

  	struct pci_dev *dev;

  	struct xen_pcibk_dev_data *dev_data = NULL;

  	struct xen_pci_op *op = &pdev->op;

  	int test_intx = 0;

  	*op = pdev->sh_info->op;
  	barrier();

  	dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);

  
  	if (dev == NULL)
  		op->err = XEN_PCI_ERR_dev_not_found;
  	else {

  		dev_data = pci_get_drvdata(dev);
  		if (dev_data)
  			test_intx = dev_data->enable_intx;

  		switch (op->cmd) {
  		case XEN_PCI_OP_conf_read:

  			op->err = xen_pcibk_config_read(dev,

  				  op->offset, op->size, &op->value);
  			break;
  		case XEN_PCI_OP_conf_write:

  			op->err = xen_pcibk_config_write(dev,

  				  op->offset, op->size,	op->value);
  			break;
  #ifdef CONFIG_PCI_MSI
  		case XEN_PCI_OP_enable_msi:

  			op->err = xen_pcibk_enable_msi(pdev, dev, op);

  			break;
  		case XEN_PCI_OP_disable_msi:

  			op->err = xen_pcibk_disable_msi(pdev, dev, op);

  			break;
  		case XEN_PCI_OP_enable_msix:

  			op->err = xen_pcibk_enable_msix(pdev, dev, op);

  			break;
  		case XEN_PCI_OP_disable_msix:

  			op->err = xen_pcibk_disable_msix(pdev, dev, op);

  			break;
  #endif
  		default:
  			op->err = XEN_PCI_ERR_not_implemented;
  			break;
  		}
  	}

  	if (!op->err && dev && dev_data) {
  		/* Transition detected */
  		if ((dev_data->enable_intx != test_intx))

  			xen_pcibk_control_isr(dev, 0 /* no reset */);

  	}

  	pdev->sh_info->op.err = op->err;
  	pdev->sh_info->op.value = op->value;
  #ifdef CONFIG_PCI_MSI
  	if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
  		unsigned int i;
  
  		for (i = 0; i < op->value; i++)
  			pdev->sh_info->op.msix_entries[i].vector =
  				op->msix_entries[i].vector;
  	}
  #endif

  	/* Tell the driver domain that we're done. */
  	wmb();
  	clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
  	notify_remote_via_irq(pdev->evtchn_irq);
  
  	/* Mark that we're done. */

  	smp_mb__before_atomic(); /* /after/ clearing PCIF_active */

  	clear_bit(_PDEVF_op_active, &pdev->flags);

  	smp_mb__after_atomic(); /* /before/ final check for work */

  
  	/* Check to see if the driver domain tried to start another request in
  	 * between clearing _XEN_PCIF_active and clearing _PDEVF_op_active.
  	*/

  	xen_pcibk_test_and_schedule_op(pdev);

  }

  irqreturn_t xen_pcibk_handle_event(int irq, void *dev_id)

  {

  	struct xen_pcibk_device *pdev = dev_id;

  	xen_pcibk_test_and_schedule_op(pdev);

  
  	return IRQ_HANDLED;
  }

  static irqreturn_t xen_pcibk_guest_interrupt(int irq, void *dev_id)

  {
  	struct pci_dev *dev = (struct pci_dev *)dev_id;

  	struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(dev);

  
  	if (dev_data->isr_on && dev_data->ack_intr) {
  		dev_data->handled++;
  		if ((dev_data->handled % 1000) == 0) {
  			if (xen_test_irq_shared(irq)) {

  				pr_info("%s IRQ line is not shared "

  					"with other domains. Turning ISR off
  ",
  					 dev_data->irq_name);
  				dev_data->ack_intr = 0;
  			}
  		}
  		return IRQ_HANDLED;
  	}
  	return IRQ_NONE;
  }