PCI: use _CRS for PCI resource allocation

Use _CRS for PCI resource allocation

This patch resolves an issue where incorrect PCI memory and i/o ranges
are being assigned to hotplugged PCI devices on some IBM systems.  The
resource mis-allocation not only makes the PCI device unuseable but
often makes the entire system unuseable due to resulting machine checks.

The hotplug capable PCI slots on the affected systems are not located
under a standard P2P bridge but are instead located under PCI root
bridges or subtractive decode P2P bridges.  For example, the IBM x3850
contains 2 hotplug capable PCI-X slots and 4 hotplug capable PCIe slots
with the PCI-X slots each located under a PCI root bridge and the PCIe
slots each located under a subtractive decode P2P bridge.

The current i386/x86_64 PCI resource allocation code does not use _CRS
returned resource information.  No other resource information source is
available for slots that are not below a standard P2P bridge so
incorrect ranges are being allocated from e820 hole causing the bad
result.

This patch causes the kernel to use _CRS returned resource info.  It is
roughly based on a change provided by Matthew Wilcox for the ia64 kernel
in 2005.  Due to possible buggy BIOS factor and possible yet to be
discovered kernel issues the function is disabled by default and can be
enabled with pci=use_crs.

Signed-off-by: Gary Hade <gary.hade@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/arch/x86/pci/pci.h b/arch/x86/pci/pci.h
index 057f335..ac56d39 100644
--- a/arch/x86/pci/pci.h
+++ b/arch/x86/pci/pci.h
@@ -27,6 +27,7 @@
 #define PCI_BIOS_IRQ_SCAN	0x2000
 #define PCI_ASSIGN_ALL_BUSSES	0x4000
 #define PCI_CAN_SKIP_ISA_ALIGN	0x8000
+#define PCI_USE__CRS		0x10000
 
 extern unsigned int pci_probe;
 extern unsigned long pirq_table_addr;