From: Mark McLoughlin <markmc@redhat.com>
Date: Tue, 14 Apr 2009 18:44:06 +0100
Subject: [pci] pci-stub module to reserve pci device
Message-id: 1239731046.8530.97.camel@blaa
O-Subject: [RHEL5.4 PATCH 5/5] [pci] pci-stub module to reserve pci device
Bugzilla: 491842
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>
RH-Acked-by: Don Dutile <ddutile@redhat.com>
RH-Acked-by: Chris Wright <chrisw@redhat.com>

https://bugzilla.redhat.com/491842

When doing device assignment with KVM there's currently nothing to
protect the device from having a driver in the host as well as the guest.
This trivial module just binds the pci device on the host to a stub
driver so that a real host driver can't bind to the device.  It has no
pci id table, it supports only dynamic ids.

 # echo "8086 10f5" > /sys/bus/pci/drivers/pci-stub/new_id
 # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
 # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/pci-stub/bind
 # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
 lrwxrwxrwx 1 root root 0 2008-11-25 19:10 /sys/bus/pci/devices/0000:00:19.0/driver -> ../../../bus/pci/drivers/pci-stub

This is a backport of a patch first included upstream in 2.6.29:

  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=c70e0d9dfe

Signed-off-by: Mark McLoughlin <markmc@redhat.com>

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 14e6e02..3ea7c11 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -27,3 +27,11 @@ config PCI_DEBUG
 
 	  When in doubt, say N.
 
+config PCI_STUB
+	tristate "PCI Stub driver"
+	depends on PCI
+	help
+	  Say Y or M here if you want be able to reserve a PCI device
+	  when it is going to be assigned to a guest operating system.
+
+	  When in doubt, say N.
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 6d93152..e992c35 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -46,6 +46,8 @@ ifndef CONFIG_X86
 obj-y += syscall.o
 endif
 
+obj-$(CONFIG_PCI_STUB) += pci-stub.o
+
 ifeq ($(CONFIG_PCI_DEBUG),y)
 EXTRA_CFLAGS += -DDEBUG
 endif
diff --git a/drivers/pci/pci-stub.c b/drivers/pci/pci-stub.c
new file mode 100644
index 0000000..74fbec0
--- /dev/null
+++ b/drivers/pci/pci-stub.c
@@ -0,0 +1,47 @@
+/* pci-stub - simple stub driver to reserve a pci device
+ *
+ * Copyright (C) 2008 Red Hat, Inc.
+ * Author:
+ * 	Chris Wright
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Usage is simple, allocate a new id to the stub driver and bind the
+ * device to it.  For example:
+ * 
+ * # echo "8086 10f5" > /sys/bus/pci/drivers/pci-stub/new_id
+ * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/e1000e/unbind
+ * # echo -n 0000:00:19.0 > /sys/bus/pci/drivers/pci-stub/bind
+ * # ls -l /sys/bus/pci/devices/0000:00:19.0/driver
+ * .../0000:00:19.0/driver -> ../../../bus/pci/drivers/pci-stub
+ */
+
+#include <linux/module.h>
+#include <linux/pci.h>
+
+static int pci_stub_probe(struct pci_dev *dev, const struct pci_device_id *id)
+{
+	return 0;
+}
+
+static struct pci_driver stub_driver = {
+	.name		= "pci-stub",
+	.id_table	= NULL,	/* only dynamic id's */
+	.probe		= pci_stub_probe,
+};
+
+static int __init pci_stub_init(void)
+{
+	return pci_register_driver(&stub_driver);
+}
+
+static void __exit pci_stub_exit(void)
+{
+	pci_unregister_driver(&stub_driver);
+}
+
+module_init(pci_stub_init);
+module_exit(pci_stub_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Chris Wright <chrisw@sous-sol.org>");