ppc manual paging question

[Nicholas Mc Guire]

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>
>  I've got some qeustion about ppc(ppc44x) paging:
>
> how can I manually map a virtual address to a physical address through a
> specific pgd? How does ppc translate virt address to physical one? I think
> besides from tlb, the CPU will search the page table entries via the pgd, can
> I alter the pgd value to change the memory translation? under i386, it's very
> simple, we can just rewrite %%cr3, it even could invalidate all tlb entries
> automatically, how can I do this under ppc? I've tried rewrite
> current->mm->pgd and current->thread.pgdir, but sounds like it still not
> insufficiant, am I missing something vital?
>

sur ! same thing flush the tlb 
or you will be totally inconsistant - actually the box should not
have survived this treatment in a stable manner. You might want to
look at kernel/ppc-stub.c as a good reference - its a similar problem
gdb also writes into memory without the kernel knowing about it - that
is comparable to what XM is doing - the solution flush the cache/tlb
all over the place - now flushing the cache is evil - but I would do
it for now and we can check alternatives and optimizations later - for
now brute force is the way to go.

for 4xx dont forget to isync after fidling with pgd/pte (see set_context
in entry_4xx.S . As far as I understand 4xx all you would really need to
do is clear the TLB entry and then you get an exception and that is
handled via 0x1100/0x1200 D/I respectively (head_4xx.S) - admitedly Im
not up to this task - need to give the manuals a lock my self to 
understand whats going on there ;)

hofrat
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