> For whatever we don't know about, why should
we assume 64-bit BARs
> work? Especially considering it's likely to be pretty old guests.
There's no need to assume 64 bit BARs works.
But I think we can assume guests don't crash.
What windows does here is very unusual imho,
guest should just say "I can't use this range
so I won't" and allocate BARs somewhere else.
Why windows crashes or what it should do doesn't matter. We have to
deal with it.
Today we have a pretty simple logic in seabios: When we run out of
space in the 32bit pci memory window we'll enable the 64bit window and
try to move 64bit bars there. So with a usual configuration there is no
64bit window simply because it isn't needed. WinXP is happy. If you
plug in pci devices with large 64bit bars the 64bit window shows up.
So, how about simply keeping that logic?
We can drop the etc/pci-info logic then.
We'll need some way for seabios to fill in the pci window information
into the qemu-provided tables. Easiest way to do that would be to
extend the COMMAND_ADD_POINTER bios linker script command.
We probably also need some knob asking seabios to enable the 64bit
window unconditionally, so we have some address space for hotplugging
pci devices with large bars.