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>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 692671b11667381516b9d95101e26415c10e35fc..d549bbc93cddf7d55f7b1193692e7bb8a330ae87 100644 (file)
--- 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;