On P2P bridges with 32-bit I/O decoding, we incorrectly sign-extended
windows starting at 0x80000000 or above. In "base |= (io_base_hi << 16)",
"io_base_hi" is promoted to a signed int before being extended to an
unsigned long.
This would cause a window starting at I/O address 0x80000000 to be
treated as though it started at 0xffffffff80008000 instead, which
should cause "no compatible bridge window" errors when we enumerate
devices using that I/O space.
The mmio and mmio_pref casts are not strictly necessary, but without
them, correctness depends on the types of the PCI_MEMORY_RANGE_MASK and
PCI_PREF_RANGE_MASK constants, which are not obvious from reading the
local code.
Found by Coverity (CID 138747 and CID 138748).
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
8f38eaca55