PCI: ARI is a PCIe v2 feature

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.

Cc: stable@kernel.org
Acked-by: Don Dutile <ddutile@redhat.com>
Tested-by: Don Dutile <ddutile@redhat.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 692671b11667..d549bbc93cdd 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1905,7 +1905,7 @@ 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)
@@ -1923,6 +1923,11 @@ void pci_enable_ari(struct pci_dev *dev)
         if (!pos)
                 return;
 
+        /* 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))
                 return;