--- a/drivers/xen/xen-pciback/pci_stub.c	2020-03-30 21:08:39.406994339 +0200
+++ b/drivers/xen/xen-pciback/pci_stub.c	2020-03-30 20:56:18.225810279 +0200
@@ -245,6 +245,90 @@
 	return found_dev;
 }
 
+struct pcistub_args {
+	struct pci_dev *dev;
+	unsigned int dcount;
+};
+
+static int pcistub_search_dev(struct pci_dev *dev, void *data)
+{
+	struct pcistub_device *psdev;
+	struct pcistub_args *arg = data;
+	bool found_dev = false;
+	unsigned long flags;
+
+	spin_lock_irqsave(&pcistub_devices_lock, flags);
+
+	list_for_each_entry(psdev, &pcistub_devices, dev_list) {
+		if (psdev->dev == dev) {
+			found_dev = true;
+			arg->dcount++;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&pcistub_devices_lock, flags);
+
+	/* Device not owned by pcistub, someone owns it. Abort the walk */
+	if (!found_dev)
+		arg->dev = dev;
+
+	return found_dev ? 0 : 1;
+}
+
+static int pcistub_reset_dev(struct pci_dev *dev)
+{
+	struct xen_pcibk_dev_data *dev_data;
+	bool slot = false, bus = false;
+	struct pcistub_args arg = {};
+
+	if (!dev)
+		return -EINVAL;
+
+	dev_dbg(&dev->dev, "[%s]\n", __func__);
+
+	if (!pci_probe_reset_slot(dev->slot))
+		slot = true;
+	else if ((!pci_probe_reset_bus(dev->bus)) &&
+		 (!pci_is_root_bus(dev->bus)))
+		bus = true;
+
+	if (!bus && !slot)
+		return -EOPNOTSUPP;
+
+	/*
+	 * Make sure all devices on this bus are owned by the
+	 * PCI backend so that we can safely reset the whole bus.
+	 */
+	pci_walk_bus(dev->bus, pcistub_search_dev, &arg);
+
+	/* All devices under the bus should be part of pcistub! */
+	if (arg.dev) {
+		dev_err(&dev->dev, "%s device on bus 0x%x is not owned by pcistub\n",
+			pci_name(arg.dev), dev->bus->number);
+
+		return -EBUSY;
+	}
+
+	dev_dbg(&dev->dev, "pcistub owns %d devices on bus 0x%x\n",
+		arg.dcount, dev->bus->number);
+
+	dev_data = pci_get_drvdata(dev);
+	if (!pci_load_saved_state(dev, dev_data->pci_saved_state))
+		pci_restore_state(dev);
+
+	/* This disables the device. */
+	xen_pcibk_reset_device(dev);
+
+	/* Cleanup up any emulated fields */
+	xen_pcibk_config_reset_dev(dev);
+
+	dev_dbg(&dev->dev, "resetting %s device using %s reset\n",
+		pci_name(dev), slot ? "slot" : "bus");
+
+	return pci_reset_bus(dev);
+}
+
 /*
  * Called when:
  *  - XenBus state has been reconfigure (pci unplug). See xen_pcibk_remove_device
@@ -1492,6 +1576,33 @@
 }
 static DRIVER_ATTR_RW(allow_interrupt_control);
 
+static ssize_t reset_store(struct device_driver *drv, const char *buf,
+			      size_t count)
+{
+	struct pcistub_device *psdev;
+	int domain, bus, slot, func;
+	int err;
+
+	err = str_to_slot(buf, &domain, &bus, &slot, &func);
+	if (err)
+		return err;
+
+	psdev = pcistub_device_find(domain, bus, slot, func);
+	if (psdev) {
+		err = pcistub_reset_dev(psdev->dev);
+		pcistub_device_put(psdev);
+	} else {
+		err = -ENODEV;
+	}
+
+	if (!err)
+		err = count;
+
+	return err;
+}
+
+static DRIVER_ATTR_WO(reset);
+
 static void pcistub_exit(void)
 {
 	driver_remove_file(&xen_pcibk_pci_driver.driver, &driver_attr_new_slot);
@@ -1507,6 +1618,8 @@
 			   &driver_attr_irq_handlers);
 	driver_remove_file(&xen_pcibk_pci_driver.driver,
 			   &driver_attr_irq_handler_state);
+	driver_remove_file(&xen_pcibk_pci_driver.driver,
+			   &driver_attr_reset);
 	pci_unregister_driver(&xen_pcibk_pci_driver);
 }
 
@@ -1603,6 +1716,11 @@
 	if (!err)
 		err = driver_create_file(&xen_pcibk_pci_driver.driver,
 					&driver_attr_irq_handler_state);
+
+	if (!err)
+		err = driver_create_file(&xen_pcibk_pci_driver.driver,
+					 &driver_attr_reset);
+
 	if (err)
 		pcistub_exit();