Re: [Xen-devel] Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use

[Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>]

On Wed, Aug 21, 2013 at 7:19 AM, Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote:
> On Wed, Aug 21, 2013 at 04:11:25PM +0200, H. Peter Anvin wrote:
>>
>> Eep.  This should be reverted, indeed.  This isn't a manifest bug on !Xen 
>> but we
>> have gotten requests for WT support which would mean adding in the PAT but 
>> again.
>
> Please no, letme fix it. That's what I'm having in mind: don't use pse bit in 
> swap
> entry but always mark page read from swap as dirty one (it's better than 
> having
> no tracker at all and  will be the case on old machines with 32bit ptes only).

Quite frankly, unless I see a patch later today that is

 (a) obvious
 (b) explains what is going on
 (c) tested

I will be reverting the whole soft-dirty mess. I thought the
bit-mapping games it played were already too complicated (the patch to
pgtable-2level.h in commit 41bb3476b361 just makes me want to barf and
came in very late, so I'm not positive about the whole soft-dirty mess
in the first place). I really am not at all inclined to want to play
games in this area any more. It's too damn late in the release window.

            Linus

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