pci: improve io address space allocation

This patch improves the io address space allocation.  It adds a check
that the region above 0xc000 which is traditionally used for pci io
is actually big enougth.  If it isn't it tries the larger window at
0x1000.  If that is to small too it errors out.

When creating guests with multiple pci-pci bridges (and devices with
io regions behind them) the 0xc000 -> 0xffff region quickly becomes
too small.

While being at it document the io address space layout used by

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
1 file changed