xen/pciback: Have 'passthrough' option instead of XEN_PCIDEV_BACKEND_PASS and XEN_PCIDEV_BACKEND_VPCI

.. compile options. This way the user can decide during runtime whether they
want the default 'vpci' (virtual pci passthrough) or where the PCI devices
are passed in without any BDF renumbering. The option 'passthrough' allows
the user to toggle the it from 0 (vpci) to 1 (passthrough).

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

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index 1e5ba85c0d33..206c4ce030bc 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -18,6 +18,21 @@
 #define INVALID_EVTCHN_IRQ  (-1)
 struct workqueue_struct *xen_pcibk_wq;
 
+static int __read_mostly passthrough;
+module_param(passthrough, bool, S_IRUGO);
+MODULE_PARM_DESC(passthrough,
+	"Option to specify how to export PCI topology to guest:\n"\
+	" 0 - (default) Hide the true PCI topology and makes the frontend\n"\
+	"   there is a single PCI bus with only the exported devices on it.\n"\
+	"   For example, a device at 03:05.0 will be re-assigned to 00:00.0\n"\
+	"   while second device at 02:1a.1 will be re-assigned to 00:01.1.\n"\
+	" 1 - Passthrough provides a real view of the PCI topology to the\n"\
+	"   frontend (for example, a device at 06:01.b will still appear at\n"\
+	"   06:01.b to the frontend). This is similar to how Xen 2.0.x\n"\
+	"   exposed PCI devices to its driver domains. This may be required\n"\
+	"   for drivers which depend on finding their hardward in certain\n"\
+	"   bus/slot locations.");
+
 static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev)
 {
 	struct xen_pcibk_device *pdev;
@@ -710,6 +725,8 @@ static struct xenbus_driver xenbus_xen_pcibk_driver = {
 	.otherend_changed	= xen_pcibk_frontend_changed,
 };
 
+struct xen_pcibk_backend *xen_pcibk_backend;
+
 int __init xen_pcibk_xenbus_register(void)
 {
 	xen_pcibk_wq = create_workqueue("xen_pciback_workqueue");
@@ -718,6 +735,10 @@ int __init xen_pcibk_xenbus_register(void)
 			"xen_pciback_workqueue failed\n", __func__);
 		return -EFAULT;
 	}
+	xen_pcibk_backend = &xen_pcibk_vpci_backend;
+	if (passthrough)
+		xen_pcibk_backend = &xen_pcibk_passthrough_backend;
+	pr_info(DRV_NAME ": backend is %s\n", xen_pcibk_backend->name);
 	return xenbus_register_backend(&xenbus_xen_pcibk_driver);
 }