[lkml]   [2006]   [Apr]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] i386: PAE entries must have their low word cleared first
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

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2006-04-26 22:31    [W:0.053 / U:8.940 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site