Alexei A. Frounze wrote:
"Eli Gottlieb" wrote in message
...

Olumide wrote:

Hi -

I know memory mapped IO is about mapping device/controller registers to
memory space in order to reduce the number of processor instructions
(and simplify device driver writing) . My question is: are device
registers mapped to virtual memory or physical memory? I suspect the
former, and I have looked up a number of texts but everyone just seems
to skirt about the issue.

Thanks,

- Olumide


Device registers have a "physical" address that can be mapped into virtual
memory using normal paging techniques, AFAIK.


Correct for real, physical devices in non-virtualized environments. If we go
for virtual ones, we may never know what is real and what is emulated in
some way (e.g. a page fault handler would do the emulation).

Alex


Is virtualization so common now that we actually bother to think about
it? Theoretically, the same software should run on both. If it
doesn't, then I see no point in the virtualization, as it would just be
the creation of an arbitrary hardware platform that doesn't have any
real hardware.