linux-kernel - Re: [PATCH 1/1] Fixup write permission of TLB on powerpc e500 core

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Date:	Mon, 18 Jul 2011 14:02:23 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Shan Hai <haishan.bai@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, paulus@...ba.org,
	tglx@...utronix.de, walken@...gle.com, dhowells@...hat.com,
	cmetcalf@...era.com, tony.luck@...el.com,
	akpm@...ux-foundation.org, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] Fixup write permission of TLB on powerpc e500 core

On Mon, 2011-07-18 at 13:53 +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2011-07-18 at 09:14 +1000, Benjamin Herrenschmidt wrote:
> 
> > In fact, with such a flag, we could probably avoid the ifdef entirely, and
> > always go toward the PTE fixup path when called in such a fixup case, my gut
> > feeling is that this is going to be seldom enough not to hurt x86 measurably
> > but we'll have to try it out.
> > 
> > That leads to that even less tested patch:
> 
>  And here's a version that builds (still not tested :-)
> 
> Shan, can you verify whether that fixes the problem for you ?
> 
> I also had a cursory glance at the ARM code and it seems to rely on the
> same stuff as embedded powerpc does for dirty/young updates, so in
> theory it should exhibit the same problem.
> 
> I suspect the scenario is rare enough in practice in embedded workloads
> that nobody noticed until now.

Ignore that bogus send, I sent a proper one immediately after (evolution
FAIL, sorry about that)

Cheers,
Ben.


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