Re: Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use

[H. Peter Anvin]

But is there a manifest bug or not?  What is the deal with Xen?

Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote:
>On Wed, Aug 21, 2013 at 09:25:47PM +0400, Cyrill Gorcunov wrote:
>> > 
>> > However, I do find the use of PTE bits in this way somewhat
>fragile.
>> > What other potential corner cases might still remain that will
>require
>> > further games with PTE bits?
>> 
>>   OK, so this is not a bug finally. The problem is that 2 level pte
>is
>> quite small and 7th bit is the only one spare I can use for soft
>dirty
>> tracking when page get swapped out. And swap engine is very depending
>> on pte being non-present, so we are on a safe side.
>
>To make it clear: I'm working on patch that won't use pse bit for dirty
>page tracking, just give some time to cook it and test.

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