[OpenBIOS] Faulty Qemu SPARC64 IDE emulation?

Tarl Neustaedter Tarl.Neustaedter at Sun.COM
Sun Dec 13 19:07:41 CET 2009

Igor Kovalenko wrote:
> [...]
> We also need to find out how memory mappings are laid out
> preparing to run client code. It is not clear from of1275 docs.

Generally, OF is placed in high memory, and memory allocations are from 
low memory.

But there are several address spaces, which it sounds like are being 
overlapped here:

1) Actual memory
2) PCI memory space
3) PCI IO space

They are each independent address spaces. Zero in any one of them is 
independent from zero in all the others.

Note that PCI memory space is further subdivided into DMA address space 
and BAR memory space. In general on SPARC (with Openboot, at least), we 
use low addresses in PCI memory space for BARs and high addresses for 
DMA (backwards from x86 behaviour). We've found a number of devices 
which refuse to allow us to assign PCI memory space 0 to a BAR - so 
we've had to reserve the low order page of PCI memory and not assign it 
to BARs.

More information about the OpenBIOS mailing list