[openrisc] Multiprocessing and virtual memory

[mbtirado@mundivia.es]

Hello.
I've read your reply about CID bits. Thank you very much for answering 
so quickly.
Your answer has led me to a new question: how does the operative 
system the management of the virtual memory?
Let's consider two different processes running concurrently on the same 
OR1200 CPU. Could these processes have access to the entire virtual 
memory space? If so, since OR1200 doesn't use CID bits the two 
processes may use repeated virtual addresses that obviously wouldn't 
represent the same physical address, as they are two different 
processes with two different physical memory spaces.
I can think about two possible solutions to this problem:
1. The Page Table would need to be replaced with every context 
change. This solution would have an enormous penalization, so I don't 
think it would be suitable.
2. The two processes wouldn't have access to the entire virtual memory 
space, but the operative system would distribute portions of virtual 
memory that processes could use.
What I need to know is: which of these solutions (or a different one 
that I haven't thought about) would an OR1000 compatible operative 
system (as for example your porting of uCLinux) use?
Thank you for your help.
Marķa Bolado.
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