Re: [Qemu-devel] [PULL 14/28] exec: make address spaces 64-bit wide

[Mike Day]

>> > > >>>>>>>
>> > > >>>>>>>>> Prior to this change, there was no re-map with the 
>> > > >>>>>>>>> fffffffffebe0000

> If we choose not to map them, how do we distinguish them from guest RAM?
> There's no MemoryRegion flag that I'm aware of to distinguish a ram_ptr
> that points to a chunk of guest memory from one that points to the mmap
> of a device BAR.  I think I'd need to explicitly walk all of the vfio
> device and try to match the MemoryRegion pointer to one of my devices.
> That only solves the problem for vfio devices and not ivshmem devices or
> pci-assign devices.
>

I don't know if this will save you doing your memory region search or
not. But a BAR that ends with the low bit set is MMIO, and BAR that
ends with the low bit clear is RAM. So the address above is RAM as was
pointed out earlier in the thread. If you got an ambitious address in
the future you could test the low bit. But MMIO is deprecated
according to http://wiki.osdev.org/PCI so you probably won't see it,
at least for 64-bit addresses.

Mike