linux-kernel - Re: [PATCH 2/4] powerpc32: properly clear page table when 0 is not a good default PTE value

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Message-ID: <1418256437.5581.51.camel@freescale.com>
Date:	Wed, 10 Dec 2014 18:07:17 -0600
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 2/4] powerpc32: properly clear page table when 0 is not
 a good default PTE value

On Wed, 2014-12-10 at 19:00 +0100, Christophe Leroy wrote:
> Some HW invert some PTE bits. In some case, __pte(0) is not 0 so the PTEs shall
> be properly set prior to being used.

__pte(0) is always zero.  If that changes in a future patch, that patch
is not doing the right thing.  The __pte()/pte_val() accesors should not
do anything beyond boxing/unboxing the value in a struct.  The right
place for special 8xx handling of the inverted bit is in pte_mkwrite()
and such.

I don't see any other architecture using __pte()/pte_val() this way.

-Scott


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