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    Subject[PATCH 5.4 032/255] PCI: Sanitise firmware BAR assignments behind a PCI-PCI bridge
    Date
    From: Maciej W. Rozycki <macro@orcam.me.uk>

    commit 0e32818397426a688f598f35d3bc762eca6d7592 upstream.

    When pci_assign_resource() is unable to assign resources to a BAR, it uses
    pci_revert_fw_address() to fall back to a firmware assignment (if any).
    Previously pci_revert_fw_address() assumed all addresses could reach the
    device, but this is not true if the device is below a bridge that only
    forwards addresses within its windows.

    This problem was observed on a Tyan Tomcat IV S1564D system where the BIOS
    did not assign valid addresses to several bridges and USB devices:

    pci 0000:00:11.0: PCI-to-PCIe bridge to [bus 01-ff]
    pci 0000:00:11.0: bridge window [io 0xe000-0xefff]
    pci 0000:01:00.0: PCIe Upstream Port to [bus 02-ff]
    pci 0000:01:00.0: bridge window [io 0x0000-0x0fff] # unreachable
    pci 0000:02:02.0: PCIe Downstream Port to [bus 05-ff]
    pci 0000:02:02.0: bridge window [io 0x0000-0x0fff] # unreachable
    pci 0000:05:00.0: PCIe-to-PCI bridge to [bus 06-ff]
    pci 0000:05:00.0: bridge window [io 0x0000-0x0fff] # unreachable
    pci 0000:06:08.0: USB UHCI 1.1
    pci 0000:06:08.0: BAR 4: [io 0xfce0-0xfcff] # unreachable
    pci 0000:06:08.1: USB UHCI 1.1
    pci 0000:06:08.1: BAR 4: [io 0xfce0-0xfcff] # unreachable
    pci 0000:06:08.0: can't claim BAR 4 [io 0xfce0-0xfcff]: no compatible bridge window
    pci 0000:06:08.1: can't claim BAR 4 [io 0xfce0-0xfcff]: no compatible bridge window

    During the first pass of assigning unassigned resources, there was not
    enough I/O space available, so we couldn't assign the 06:08.0 BAR and
    reverted to the firmware assignment (still unreachable). Reverting the
    06:08.1 assignment failed because it conflicted with 06:08.0:

    pci 0000:00:11.0: bridge window [io 0xe000-0xefff]
    pci 0000:01:00.0: no space for bridge window [io size 0x2000]
    pci 0000:02:02.0: no space for bridge window [io size 0x1000]
    pci 0000:05:00.0: no space for bridge window [io size 0x1000]
    pci 0000:06:08.0: BAR 4: no space for [io size 0x0020]
    pci 0000:06:08.0: BAR 4: trying firmware assignment [io 0xfce0-0xfcff]
    pci 0000:06:08.1: BAR 4: no space for [io size 0x0020]
    pci 0000:06:08.1: BAR 4: trying firmware assignment [io 0xfce0-0xfcff]
    pci 0000:06:08.1: BAR 4: [io 0xfce0-0xfcff] conflicts with 0000:06:08.0 [io 0xfce0-0xfcff]

    A subsequent pass assigned valid bridge windows and a valid 06:08.1 BAR,
    but left the 06:08.0 BAR alone, so the UHCI device was still unusable:

    pci 0000:00:11.0: bridge window [io 0xe000-0xefff] released
    pci 0000:00:11.0: bridge window [io 0x1000-0x2fff] # reassigned
    pci 0000:01:00.0: bridge window [io 0x1000-0x2fff] # reassigned
    pci 0000:02:02.0: bridge window [io 0x2000-0x2fff] # reassigned
    pci 0000:05:00.0: bridge window [io 0x2000-0x2fff] # reassigned
    pci 0000:06:08.0: BAR 4: assigned [io 0xfce0-0xfcff] # left alone
    pci 0000:06:08.1: BAR 4: assigned [io 0x2000-0x201f]
    ...
    uhci_hcd 0000:06:08.0: host system error, PCI problems?
    uhci_hcd 0000:06:08.0: host controller process error, something bad happened!
    uhci_hcd 0000:06:08.0: host controller halted, very bad!
    uhci_hcd 0000:06:08.0: HCRESET not completed yet!
    uhci_hcd 0000:06:08.0: HC died; cleaning up

    If the address assigned by firmware is not reachable because it's not
    within upstream bridge windows, fail instead of assigning the unusable
    address from firmware.

    [bhelgaas: commit log, use pci_upstream_bridge()]
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=16263
    Link: https://lore.kernel.org/r/alpine.DEB.2.21.2203012338460.46819@angie.orcam.me.uk
    Link: https://lore.kernel.org/r/alpine.DEB.2.21.2209211921250.29493@angie.orcam.me.uk
    Fixes: 58c84eda0756 ("PCI: fall back to original BIOS BAR addresses")
    Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    Cc: stable@vger.kernel.org # v2.6.35+
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/pci/setup-res.c | 11 +++++++++++
    1 file changed, 11 insertions(+)

    --- a/drivers/pci/setup-res.c
    +++ b/drivers/pci/setup-res.c
    @@ -209,6 +209,17 @@ static int pci_revert_fw_address(struct

    root = pci_find_parent_resource(dev, res);
    if (!root) {
    + /*
    + * If dev is behind a bridge, accesses will only reach it
    + * if res is inside the relevant bridge window.
    + */
    + if (pci_upstream_bridge(dev))
    + return -ENXIO;
    +
    + /*
    + * On the root bus, assume the host bridge will forward
    + * everything.
    + */
    if (res->flags & IORESOURCE_IO)
    root = &ioport_resource;
    else

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