• Alexey Kardashevskiy's avatar
    powerpc/pci/of: Fix OF flags parsing for 64bit BARs · 43799f0d
    Alexey Kardashevskiy authored
    BugLink: https://bugs.launchpad.net/bugs/1840081
    
    [ Upstream commit df5be5be ]
    
    When the firmware does PCI BAR resource allocation, it passes the assigned
    addresses and flags (prefetch/64bit/...) via the "reg" property of
    a PCI device device tree node so the kernel does not need to do
    resource allocation.
    
    The flags are stored in resource::flags - the lower byte stores
    PCI_BASE_ADDRESS_SPACE/etc bits and the other bytes are IORESOURCE_IO/etc.
    Some flags from PCI_BASE_ADDRESS_xxx and IORESOURCE_xxx are duplicated,
    such as PCI_BASE_ADDRESS_MEM_PREFETCH/PCI_BASE_ADDRESS_MEM_TYPE_64/etc.
    When parsing the "reg" property, we copy the prefetch flag but we skip
    on PCI_BASE_ADDRESS_MEM_TYPE_64 which leaves the flags out of sync.
    
    The missing IORESOURCE_MEM_64 flag comes into play under 2 conditions:
    1. we remove PCI_PROBE_ONLY for pseries (by hacking pSeries_setup_arch()
    or by passing "/chosen/linux,pci-probe-only");
    2. we request resource alignment (by passing pci=resource_alignment=
    via the kernel cmd line to request PAGE_SIZE alignment or defining
    ppc_md.pcibios_default_alignment which returns anything but 0). Note that
    the alignment requests are ignored if PCI_PROBE_ONLY is enabled.
    
    With 1) and 2), the generic PCI code in the kernel unconditionally
    decides to:
    - reassign the BARs in pci_specified_resource_alignment() (works fine)
    - write new BARs to the device - this fails for 64bit BARs as the generic
    code looks at IORESOURCE_MEM_64 (not set) and writes only lower 32bits
    of the BAR and leaves the upper 32bit unmodified which breaks BAR mapping
    in the hypervisor.
    
    This fixes the issue by copying the flag. This is useful if we want to
    enforce certain BAR alignment per platform as handling subpage sized BARs
    is proven to cause problems with hotplug (SLOF already aligns BARs to 64k).
    Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
    Reviewed-by: default avatarSam Bobroff <sbobroff@linux.ibm.com>
    Reviewed-by: default avatarOliver O'Halloran <oohall@gmail.com>
    Reviewed-by: default avatarShawn Anastasio <shawn@anastas.io>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    Signed-off-by: default avatarConnor Kuehl <connor.kuehl@canonical.com>
    Signed-off-by: default avatarKleber Sacilotto de Souza <kleber.souza@canonical.com>
    43799f0d
pci_of_scan.c 11.4 KB