On 23.12.2009, at 07:12, Aurelien Jarno wrote: > On Tue, Dec 22, 2009 at 02:45:17PM +0100, Alexander Graf wrote: >> When we get an MMIO request, we always get variables in host endianness. The >> only time we need to actually reverse byte order is when we read bytes from >> guest memory. >> >> Apparently the DBDMA implementation is different there. A lot of the logic >> in there depends on values being big endian. Now, qemu does all the >> conversion >> in the MMIO handlers for us already though, so it turns out that we're in >> the same byte order from a C point of view, but cpu_to_be32 and be32_to_cpu >> end up being nops. >> >> This makes the code work differently on x86 (little endian) than on ppc (big >> endian). On x86 it works, on ppc it doesn't. >> >> This patch (while being seriously hacky and ugly) makes dbdma emulation work >> on ppc hosts. I'll leave the real fixing to someone else. > > I have to say I found it too hacky to be included in QEMU. I would > prefer if someone can provide a real fix.
Looking at hw/pci_host_template.h I'm actually more confident now that this is actually the correct solution. We don't want big endian or little endian, we want reversed endian variables. Alex
