xen: initialize platform-pci even if xen_emul_unplug=never

When xen_emul_unplug=never is specified on kernel command line
reading files from /sys/hypervisor is broken (returns -EBUSY).
It is caused by xen_bus dependency on platform-pci and
platform-pci isn't initialized when xen_emul_unplug=never is
specified.

Fix it by allowing platform-pci to ignore xen_emul_unplug=never,
and do not intialize xen_[blk|net]front instead.
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkfront.c

@@ -1452,6 +1452,9 @@ static int __init xlblk_init(void)
 	if (!xen_domain())
 		return -ENODEV;
 
+	if (!xen_platform_pci_unplug)
+		return -ENODEV;
+
 	if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
 		printk(KERN_WARNING "xen_blk: can't get major %d with name %s\n",
 		       XENVBD_MAJOR, DEV_NAME);

drivers/net/xen-netfront.c

@@ -47,6 +47,7 @@
 #include <xen/xenbus.h>
 #include <xen/events.h>
 #include <xen/page.h>
+#include <xen/platform_pci.h>
 #include <xen/grant_table.h>
 
 #include <xen/interface/io/netif.h>
@@ -1956,6 +1957,9 @@ static int __init netif_init(void)
 	if (xen_initial_domain())
 		return 0;
 
+	if (!xen_platform_pci_unplug)
+		return -ENODEV;
+
 	printk(KERN_INFO "Initialising Xen virtual ethernet driver.\n");
 
 	return xenbus_register_frontend(&netfront_driver);

drivers/xen/platform-pci.c

@@ -186,11 +186,6 @@ static struct pci_driver platform_driver = {
 
 static int __init platform_pci_module_init(void)
 {
-	/* no unplug has been done, IGNORE hasn't been specified: just
-	 * return now */
-	if (!xen_platform_pci_unplug)
-		return -ENODEV;
-
 	return pci_register_driver(&platform_driver);
 }