From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@ozlabs.org>,
Paul Mackerras <paulus@samba.org>,
Kumar Gala <galak@gate.crashing.org>
Subject: Re: Should ppc32 use CONFIG_HIGHPTE or not?
Date: Sat, 02 May 2009 06:14:07 +1000 [thread overview]
Message-ID: <1241208847.1781.6.camel@pasglop> (raw)
In-Reply-To: <1241203023.29485.218.camel@nimitz>
On Fri, 2009-05-01 at 11:37 -0700, Dave Hansen wrote:
.../...
> So, it looks like ppc32 never actually allocates highmem pte pages, but
> it *does* go to the trouble of at least trying to kmap_atomic() them.
> Should we just give ppc32 unconditional direct-mapped ptes? Or, should
> we remove that #ifdef and let it allocate them in highmem when it can
> since we also have the code to support that?
We actually noticed that recently :-)
We implemented HIGHPTE support a long time ago, and then somebody
disabled HIGHPTE for both x86 and powerpc on the ground that it wasn't
reliable, I don't remember off hand who, I think it was in the 2.5.x
timeframe, and while it got re-enabled on x86 it never was on powerpc
(maybe because we never noticed it was disabled in the first place ;-)
Now, recently, some changes went in that could possibly be problematic
with HIGHPTE, at least I have a vague recollection of that, I think
Kumar was involved... Kumar, was this fixed ?
So depending on that, maybe we could revive the option ... or just
get rid of that HIGHPTE support and be done with it.
Cheers,
Ben.
prev parent reply other threads:[~2009-05-01 20:14 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-01 18:37 Should ppc32 use CONFIG_HIGHPTE or not? Dave Hansen
2009-05-01 20:14 ` Benjamin Herrenschmidt [this message]
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