From: Don Dutile <ddutile@redhat.com>
Date: Fri, 15 May 2009 11:51:18 -0400
Subject: [pci] remove pci-stub driver from -xen kernels
Message-id: 4A0D8F76.50902@redhat.com
O-Subject: [RHEL5.4 PATCH] Remove pci-stub driver from -xen kernels
Bugzilla: 500568
RH-Acked-by: Rik van Riel <riel@redhat.com>
RH-Acked-by: Chris Lalancette <clalance@redhat.com>
RH-Acked-by: Justin M. Forbes <jforbes@redhat.com>

BZ 500568

 From the BZ:

The latest kernel-xen has the newly backported pci-stub driver built-in to the
kernel by default.

This causes a problem in handling of PCI passthrough to guest VMs, because
libvirt sees that pci-stub is present and uses that.  XenD in RHEL-5, however,
*requires* that pciback is used and cannot work with pci-stub. It is not even
possible to workaround this by blacklisting the pci-stub because it was
compiled into the kernel, not built as a module.

We need to turn off pci-stub for kernel-xen builds, and only have it in
bare-metal builds for use with KVM

Removed pci-stub driver from -xen kernel by:
(a) setting CONFIG_PCI_STUB=n in generic-xen config file
(b) setting drivers/pci/Kconfig for PCI_STUB to depend on !XEN
(c) adding ifndef XEN endif around pci-stub inclusion in drivers/pci/Makefile

/me puts sledgehammer away.

Simple build testing:
Local build of config files in RHEL5 git tree (make rh-configs-prep)
showed that CONFIG_PCI_STUB=y no longer in -xen config files.
scan of non-xen-kernel config files showed CONFIG_PCI_STUB=y still there.
Rebuilt the x86-64 xen kernel to ensure it built correctly w/o pci-stub.o
Rebuilt the x86_64 non-xen kernel to ensure pci-stub was included in it.

Please review & ack.

- Don

ps -- danpb: if you can test the patch with the tool set you
       filed the bz under, that'd be appreciated.

diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index bc6a162..45fd204 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -29,7 +29,7 @@ config PCI_DEBUG
 
 config PCI_STUB
 	tristate "PCI Stub driver"
-	depends on PCI
+	depends on PCI && !XEN
 	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.
diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
index 4d24d84..c16fa95 100644
--- a/drivers/pci/Makefile
+++ b/drivers/pci/Makefile
@@ -49,7 +49,9 @@ ifndef CONFIG_X86
 obj-y += syscall.o
 endif
 
+ifndef CONFIG_XEN
 obj-$(CONFIG_PCI_STUB) += pci-stub.o
+endif
 
 ifeq ($(CONFIG_PCI_DEBUG),y)
 EXTRA_CFLAGS += -DDEBUG