Subject: Re: [PATCH] powerpc/8xx: fix regression introduced by cache coherency rewrite

From: Benjamin Herrenschmidt <[email-masked]>
Date: Fri, 25 Sep 2009 11:51:20 +1000

On Thu, 2009-09-24 at 18:35 -0700, Rex Feany wrote:
> 
> Then I can boot and get to a shell, but userspace is slow. 8 seconds
> to mount
> /proc (vs. less then a second using my old kernel)! Maybe this is an
> unrelated issue?  I'm pretty clueless about the details, I'm sorry.
> PG_arch_1 is used to prevent a cache flush unless it is actually
> needed?
> Then why would changing the location of the tlbil_va() make a
> difference?

I think there's more finishyness to 8xx than we thought. IE. That
tlbil_va might have more reasons to be there than what the comment
seems to advertize. Can you try to move it even higher up ? IE.
Unconditionally at the beginning of set_pte_filter ?

Also, if that doesn't help, can you try putting one in
set_access_flags_filter() just below ?

(Beware that there's two different versions of both functions, only the
first one is compiled/used on 8xx).

It's going to be hard for me to get that "right" since I don't really
know what's going on with the core here, but I suppose if we get it
moving along with extra tlb invalidations, that should be "good enough"
until somebody who really knows what's going on comes up with possibly
a better fix.

Cheers,
Ben.