x86/PCI: config space accessor functions should not ignore the segment argument

Without this change, the majority of the raw PCI config space access
functions silently ignore a non-zero segment argument, which is
certainly wrong.

Apart from pci_direct_conf1, all other non-MMCFG access methods get
used only for non-extended accesses (i.e. assigned to raw_pci_ops
only). Consequently, with the way raw_pci_{read,write}() work, it would
be a coding error to call these functions with a non-zero segment (with
the current call flow this cannot happen afaict).

The access method 1 accessor, as it can be used for extended accesses
(on AMD systems) instead gets checks added for the passed in segment to
be zero. This would be the case when on such a system having multiple
PCI segments (don't know whether any exist in practice) MMCFG for some
reason is not usable, and method 1 gets selected for doing extended
accesses. Rather than accessing the wrong device's config space, the
function will now error out.

v2: Convert BUG_ON() to WARN_ON(), and extend description as per Ingo's
request.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
index a5f7d0d63de0..f68553551467 100644
--- a/arch/x86/pci/pcbios.c
+++ b/arch/x86/pci/pcbios.c
@@ -181,6 +181,7 @@ static int pci_bios_read(unsigned int seg, unsigned int bus,
 	unsigned long flags;
 	unsigned long bx = (bus << 8) | devfn;
 
+	WARN_ON(seg);
 	if (!value || (bus > 255) || (devfn > 255) || (reg > 255))
 		return -EINVAL;
 
@@ -247,6 +248,7 @@ static int pci_bios_write(unsigned int seg, unsigned int bus,
 	unsigned long flags;
 	unsigned long bx = (bus << 8) | devfn;
 
+	WARN_ON(seg);
 	if ((bus > 255) || (devfn > 255) || (reg > 255)) 
 		return -EINVAL;