Re: [PATCH 2/6] 8xx: get rid of _PAGE_HWWRITE dependency in MMU.

Benjamin Herrenschmidt [off-list ref] wrote on 08/10/2009 02:28:19:

On Thu, 2009-10-08 at 02:19 +0200, Joakim Tjernlund wrote:

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Benjamin Herrenschmidt [off-list ref] wrote on 08/10/2009 02:04:56:

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Yes it does. If one adds HWEXEC it will fail, right?

Why ? We can just filter out DSISR, we don't really care why it failed
as long as we know whether it was a store or not.

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Also this count as a read and you could easily end up
in the protection case(in 2.4 you do)

I'm not sure what you mean by "the protection case" Again, the C code
shouldn't care.

it does, and it should. How else should you know if you try
to read a NA space?

Generic code should sort it out in handle_mm_fault() (or earlier if it
can't find a VMA at all).

How can it? You need to know more that just read and write.

The DSISR munging is really not necessary I believe.

Well, it is today and I don't see how you can remove it.

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2.4 and 2.6 have the same handling in asm.

Yeah but the C code, especially the generic part, is different.

yes, but it seem to work the same.

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hmm, maybe I should just call C, but 8xx isn't a speed monster so every
cycle counts :)

But that's a slow path anyways.

How so? You take a TLB Error for the first write to
every page.

 Jocke