Re: [Qemu-devel] [Qemu-ppc] [PATCH v3 11/14] ioport: Switch dispatching to memory core layer

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Fri, 2013-07-12 at 05:18 +0200, Alexander Graf wrote:
> We model a single system wide io space today and access to that one
> happens through you pci host controller. I just messed up the
> terminology here.

Single system wide IO space is broken. We have separate IO space per
PHB. That was working afaik.

In any case, I completely object to all that business with conversion in
bridges.

That's fundamentally WRONG.

The whole business of endianness in qemu is a mess. In the end what
matters and the only thing that does is:

 * The endianness of a given memory access by the guest (which may or
may not be the endianness of the guest -> MSR:LE, byteswap load/store
instsructions, etc..)

vs.

 * The endianness of the target device register (and I say register ...
a framebuffer does NOT have endianness per-se and thus accesses to BAR
mapping a "memory" range (framebuffer, ROM, ...) should go such that the
*byte order* of individual bytes is preserved, which typically means
untranslated).

Unless they are completely broken (and those exist, don't get me wrong,
though mostly they are a thing of a past long gone), bridges and busses
have no effect on endianness.

So I'm not sure what you guys are up to, but from what I read, it's
wrong, and the fact at this stage is that your broke IO space (and thus
virtio and VGA) on powerpc (including pseries).

Cheers,
Ben.