xen/pciback: Allocate IRQ handler for device that is shared with guest.

If the device that is to be shared with a guest is a level device and
the IRQ is shared with the initial domain we need to take actions.
Mainly we install a dummy IRQ handler that will ACK on the interrupt
line so as to not have the initial domain disable the interrupt line.

This dummy IRQ handler is not enabled when the device MSI/MSI-X lines
are set, nor for edge interrupts. And also not for level interrupts
that are not shared amongst devices. Lastly, if the user passes
to the guest all of the PCI devices on the shared line the we won't
install the dummy handler either.

There is also SysFS instrumentation to check its state and turn
IRQ ACKing on/off if necessary.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 87 insertions, 3 deletions

diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index ac8396d8206b..c4d1071ebbe6 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -21,6 +21,8 @@
 #include "conf_space.h"
 #include "conf_space_quirks.h"
 
+#define DRV_NAME	"pciback"
+
 static char *pci_devs_to_hide;
 wait_queue_head_t aer_wait_queue;
 /*Add sem for sync AER handling and pciback remove/reconfigue ops,
@@ -290,13 +292,20 @@ static int __devinit pcistub_init_device(struct pci_dev *dev)
 	 * would need to be called somewhere to free the memory allocated
 	 * here and then to call kfree(pci_get_drvdata(psdev->dev)).
 	 */
-	dev_data = kzalloc(sizeof(*dev_data), GFP_ATOMIC);
+	dev_data = kzalloc(sizeof(*dev_data) +  strlen(DRV_NAME "[]")
+				+ strlen(pci_name(dev)) + 1, GFP_ATOMIC);
 	if (!dev_data) {
 		err = -ENOMEM;
 		goto out;
 	}
 	pci_set_drvdata(dev, dev_data);
 
+	/*
+	 * Setup name for fake IRQ handler. It will only be enabled
+	 * once the device is turned on by the guest.
+	 */
+	sprintf(dev_data->irq_name, DRV_NAME "[%s]", pci_name(dev));
+
 	dev_dbg(&dev->dev, "initializing config\n");
 
 	init_waitqueue_head(&aer_wait_queue);
@@ -837,7 +846,7 @@ static struct pci_error_handlers pciback_error_handler = {
  */
 
 static struct pci_driver pciback_pci_driver = {
-	.name = "pciback",
+	.name = DRV_NAME,
 	.id_table = pcistub_ids,
 	.probe = pcistub_probe,
 	.remove = pcistub_remove,
@@ -1029,6 +1038,72 @@ static ssize_t pcistub_slot_show(struct device_driver *drv, char *buf)
 
 DRIVER_ATTR(slots, S_IRUSR, pcistub_slot_show, NULL);
 
+static ssize_t pcistub_irq_handler_show(struct device_driver *drv, char *buf)
+{
+	struct pcistub_device *psdev;
+	struct pciback_dev_data *dev_data;
+	size_t count = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (count >= PAGE_SIZE)
+			break;
+		if (!psdev->dev)
+			continue;
+		dev_data = pci_get_drvdata(psdev->dev);
+		if (!dev_data)
+			continue;
+		count +=
+		    scnprintf(buf + count, PAGE_SIZE - count,
+			      "%s:%s:%sing:%ld\n",
+			      pci_name(psdev->dev),
+			      dev_data->isr_on ? "on" : "off",
+			      dev_data->ack_intr ? "ack" : "not ack",
+			      dev_data->handled);
+	}
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+	return count;
+}
+
+DRIVER_ATTR(irq_handlers, S_IRUSR, pcistub_irq_handler_show, NULL);
+
+static ssize_t pcistub_irq_handler_switch(struct device_driver *drv,
+					  const char *buf,
+					  size_t count)
+{
+	struct pcistub_device *psdev;
+	struct pciback_dev_data *dev_data;
+	int domain, bus, slot, func;
+	int err = -ENOENT;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		goto out;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+
+	if (!psdev)
+		goto out;
+
+	dev_data = pci_get_drvdata(psdev->dev);
+	if (!dev_data)
+		goto out;
+
+	dev_dbg(&psdev->dev->dev, "%s fake irq handler: %d->%d\n",
+		dev_data->irq_name, dev_data->isr_on,
+		!dev_data->isr_on);
+
+	dev_data->isr_on = !(dev_data->isr_on);
+	if (dev_data->isr_on)
+		dev_data->ack_intr = 1;
+out:
+	if (!err)
+		err = count;
+	return err;
+}
+DRIVER_ATTR(irq_handler_state, S_IWUSR, NULL, pcistub_irq_handler_switch);
+
 static ssize_t pcistub_quirk_add(struct device_driver *drv, const char *buf,
 				 size_t count)
 {
@@ -1168,7 +1243,10 @@ static void pcistub_exit(void)
 	driver_remove_file(&pciback_pci_driver.driver, &driver_attr_slots);
 	driver_remove_file(&pciback_pci_driver.driver, &driver_attr_quirks);
 	driver_remove_file(&pciback_pci_driver.driver, &driver_attr_permissive);
-
+	driver_remove_file(&pciback_pci_driver.driver,
+			   &driver_attr_irq_handlers);
+	driver_remove_file(&pciback_pci_driver.driver,
+			   &driver_attr_irq_handler_state);
 	pci_unregister_driver(&pciback_pci_driver);
 }
 
@@ -1227,6 +1305,12 @@ static int __init pcistub_init(void)
 		err = driver_create_file(&pciback_pci_driver.driver,
 					 &driver_attr_permissive);
 
+	if (!err)
+		err = driver_create_file(&pciback_pci_driver.driver,
+					 &driver_attr_irq_handlers);
+	if (!err)
+		err = driver_create_file(&pciback_pci_driver.driver,
+					&driver_attr_irq_handler_state);
 	if (err)
 		pcistub_exit();