From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Hugh Dickins <hugh@veritas.com>
Cc: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>,
Jan Beulich <jbeulich@novell.com>,
Zachary Amsden <zach@vmware.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] i386: PAE entries must have their low word cleared first
Date: Thu, 27 Apr 2006 02:06:37 +1000 [thread overview]
Message-ID: <444F9A8D.3040604@yahoo.com.au> (raw)
In-Reply-To: <Pine.LNX.4.64.0604261636570.11246@blonde.wat.veritas.com>
Hugh Dickins wrote:
> On Wed, 26 Apr 2006, Keir Fraser wrote:
>
>>We cannot use pte_clear() unless we redefine it for PAE. Currently it reduces
>>to set_pte() which explicitly uses the wrong ordering (sets high *then* low,
>>because it's normally used to introduce a mapping).
>
>
> I overlooked that reversal completely. What a very good point.
> I think that actually pte_clear() _does_ need to be redefined for PAE,
> to reverse that ordering as you point out. Take a look at its use in
> mm/highmem.c (where a comment states it's safe against speculative
> execution, but a comment can't guarantee that!): what do you think?
Speculative execution is safe I think (and so is ptep_get_and_clear_full,
because in neither case will the virtual address be visible).
Speculative prefetching + tlb instantiation, apparently no.
--
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com
next prev parent reply other threads:[~2006-04-26 20:28 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-26 13:46 [PATCH] i386: PAE entries must have their low word cleared first Jan Beulich
2006-04-26 14:46 ` Hugh Dickins
2006-04-26 15:06 ` Keir Fraser
2006-04-26 15:44 ` Zachary Amsden
2006-04-26 15:57 ` Hugh Dickins
2006-04-26 16:12 ` Keir Fraser
2006-04-26 15:45 ` Hugh Dickins
2006-04-26 16:06 ` Nick Piggin [this message]
2006-04-26 15:58 ` Nick Piggin
2006-04-27 10:27 ` Sonny Rao
2006-04-27 13:39 ` Nick Piggin
-- strict thread matches above, loose matches on Subject: below --
2006-04-26 22:11 Brunner, Richard
2006-04-26 22:22 ` Zachary Amsden
2006-04-26 22:27 ` Zachary Amsden
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