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Date: Wed, 26 May 2004 02:18:45 +0400
From: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Andrea Arcangeli <andrea@suse.de>, Matthew Wilcox <willy@debian.org>,
       Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Andrew Morton <akpm@osdl.org>,
       Linux Kernel list <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>, Ben LaHaise <bcrl@kvack.org>,
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Subject: Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE
Message-ID: <20040526021845.A1302@den.park.msu.ru>
References: <1085373839.14969.42.camel@gaston> <Pine.LNX.4.58.0405232149380.25502@ppc970.osdl.org> <20040525034326.GT29378@dualathlon.random> <Pine.LNX.4.58.0405242051460.32189@ppc970.osdl.org> <20040525114437.GC29154@parcelfarce.linux.theplanet.co.uk> <Pine.LNX.4.58.0405250726000.9951@ppc970.osdl.org> <20040525212720.GG29378@dualathlon.random> <Pine.LNX.4.58.0405251440120.9951@ppc970.osdl.org> <20040525215500.GI29378@dualathlon.random> <Pine.LNX.4.58.0405251500250.9951@ppc970.osdl.org>
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On Tue, May 25, 2004 at 03:01:55PM -0700, Linus Torvalds wrote:
> A "not-present" fault is a totally different fault from a "protection 
> fault". Only the not-present fault ends up walking the page tables, if I 
> remember correctly.

Precisely. The architecture reference manual says:
"Additionally, when the software changes any part (except the software
field) of a *valid* PTE, it must also execute a tbi instruction."

Ivan.