Good question... Cyrill Gorcunov <gorcu...@gmail.com> wrote: >On Wed, Aug 21, 2013 at 02:48:20PM +0100, David Vrabel wrote: >> All, >> >> 179ef71c (mm: save soft-dirty bits on swapped pages) introduces a new >> PTE bit on x86 _PTE_SWP_SOFT_DIRTY which has the same value as >_PTE_PSE >> and _PTE_PAT. >> >> With a Xen PV guest, the use of the _PTE_PAT will result in the page >> having unexpected cachability which will introduce a range of subtle >> performance and correctness issues. Xen programs the entry 4 in the >PAT >> table with WC so a page that was previously WB will end up as WC. >> > >David, could you please explain, Xen keeps and analyze _PTE_PAT bit >for ptes which are not present?
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