Re: [kvm-ppc-devel] [PATCH] RFC: Use CONFIG_HAS_IOPORTaround vcpu->pio_data

[Hollis Blanchard <hollisb-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

On Tue, 2007-12-04 at 12:39 +0800, Zhang, Xiantao wrote:
> Hollis Blanchard wrote:
> > Actually, (now that I try to build with it :) this doesn't work for
> > PowerPC, which defines (or rather, doesn't not define)
> > CONFIG_HAS_IOPORT.
> 
> You mean ppc has ioport , but you don't use current kvm io
> infrastructure to handle it ? 

It's a matter of perspective. :)

The PowerPC architecture has no "IO" instructions; therefore all IO
accesses are MMIO.

However, you can place devices with IO ports in a PowerPC system. In
this case, the bridges are configured to translate MMIO accesses coming
from the processor into IO port accesses on the bus. It is quite common
to find standard x86 ISA devices, such as a SuperIO chip, in PowerPC
systems.

In Linux, CONFIG_HAS_IOPORT doesn't really mean "does the architecture
use IO ports," which is what I thought it meant. Instead, it means
"should we track IO resources as well as MMIO resources," and that's
true on PowerPC because we need manage the ISA bus as mentioned above.
(The only current user of the symbol is lib/devres.c.)

In summary, it's an inappropriate ifdef for this situation.

-- 
Hollis Blanchard
IBM Linux Technology Center


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