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    Subject[32/55] PCI: ARI is a PCIe v2 feature
    2.6.32-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Chris Wright <chrisw@sous-sol.org>

    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@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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/pci/pci.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/drivers/pci/pci.c
    +++ b/drivers/pci/pci.c
    @@ -1507,7 +1507,7 @@ void pci_enable_ari(struct pci_dev *dev)
    {
    int pos;
    u32 cap;
    - u16 ctrl;
    + u16 flags, ctrl;
    struct pci_dev *bridge;

    if (!dev->is_pcie || dev->devfn)
    @@ -1525,6 +1525,11 @@ 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;



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