On Mon, 2010-01-04 at 23:12 +0200, Michael S. Tsirkin wrote: > Well, the main issue if I understand correcttly is that basically the > same hardware bridge can be connected to host in different ways. Yes, we > can say "if it's connected differently it's a different device" but this > is slightly ugly, device should not have to know how it's connected. It > would be cleaner to have a "connector" device in the middle that swaps > bytes. Even though yes, what you describe would be less ugly than using > proprocessor as we do now.
Well, the thing is... PCI is always little endian. I'm not 100% familiar on how emulation of devices works in qemu, but it's possible that the problem here is simply not how a standard PCI host bridge is connected to the processor changing but rather whether it's connected to an x86 host or a ppc host should make the byte order appear different. IE. a PPC operating system will byteswap accesses. If qemu just passes on accesses -as-is- instead of doing natural byteswapping then indeed you will need that added swap there too. I still think though that this should be buried in the accessors for the host bridge themselves, eventually controlled by a flag set when instanciating the host bridge in case it can indeed be wired in different ways. Cheers, Ben.
