[34-longterm 132/179] PCI: ARI is a PCIe v2 feature

From: Paul Gortmaker
Date: Mon May 14 2012 - 22:39:23 EST

From: Chris Wright <chrisw@xxxxxxxxxxxx>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 864d296cf948aef0fa32b81407541572583f7572 upstream.

The function pci_enable_ari() may mistakenly set the downstream port
of a v1 PCIe switch in ARI Forwarding mode. This is a PCIe v2 feature,
and with an SR-IOV device on that switch port believing the switch above
is ARI capable it may attempt to use functions 8-255, translating into
invalid (non-zero) device numbers for that bus. This has been seen
to cause Completion Timeouts and general misbehaviour including hangs
and panics.

Acked-by: Don Dutile <ddutile@xxxxxxxxxx>
Tested-by: Don Dutile <ddutile@xxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Jesse Barnes <jbarnes@xxxxxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
drivers/pci/pci.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 8abe983..2326637 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1713,7 +1713,7 @@ void pci_enable_ari(struct pci_dev *dev)
int pos;
u32 cap;
- u16 ctrl;
+ u16 flags, ctrl;
struct pci_dev *bridge;

if (!pci_is_pcie(dev) || dev->devfn)
@@ -1731,6 +1731,11 @@ void pci_enable_ari(struct pci_dev *dev)
if (!pos)

+ /* ARI is a PCIe v2 feature */
+ pci_read_config_word(bridge, pos + PCI_EXP_FLAGS, &flags);
+ if ((flags & PCI_EXP_FLAGS_VERS) < 2)
+ return;
pci_read_config_dword(bridge, pos + PCI_EXP_DEVCAP2, &cap);
if (!(cap & PCI_EXP_DEVCAP2_ARI))

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