Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 21 Aug 2013 12:07:13 -0700 | Subject | Re: Regression: x86/mm: new _PTE_SWP_SOFT_DIRTY bit conflicts with existing use |
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On Wed, Aug 21, 2013 at 12:03 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote: > On Wed, Aug 21, 2013 at 08:50:26PM +0200, H. Peter Anvin wrote: >> But is there a manifest bug or not? What is the deal with Xen? >> > > I personally don't see bug here because > > - this swapped page soft dirty bit is set for non-present entries only, > never for present ones, just at moment we form swap pte entry > > - i don't find any code which would test for this bit directly without > is_swap_pte call > > but the use of paw bit itself is confusing, so I'm working on patch which > won't use it. Again, if someone knows where exactly access to pse bit when > pte keeps swap entry may happen (for any purpose other than dirty page > tracking) please share.
I doubt that there are cacheability issues here, since the swap type already overlaps with PWT and PCD.
What happens if the page being swapped is a THP page? (I have no idea how, or even if, this works, but presumably PSE is important.)
--Andy
-- Andy Lutomirski AMA Capital Management, LLC
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