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

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 08 Oct 2009 11:04:56 +1100

> 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.

> 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.

> hey, I think you have to show how then :) I am not
> good at ppc shift, mask, rotate insn.

They are so fun ! :-0

> >
> > > Because if you go to C with a protection fault, you are in trouble.
> >
> > Why ?
> 
> In 2.4 you end up in read protection fault an get a SEGV back :)

We probably should ignore the DSISR bits then. So it just goes to
generic C code which then fixes up ACCESSED etc... and returns.

> Now I only handle DIRTY and the rest in C. Figured it is
> much faster and really simplie now, stay tuned.

You should not even have to handle DIRTY at all in asm. At least in 2.6.
I can't vouch for what 2.4 generic code does... You should really port
your board over :-)

Cheers,
Ben.