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Re: [Xen-devel] Writable page tables questions

At 09:55 +0000 on 06 Jan (1420534536), Ian Campbell wrote:
> The tlb flushes involved in the above are reasonably expensive, IIRC Xen
> flip flopped a bit (years ago now) on whether it is worthwhile doing
> this or not, which is why I'm not sure if it still does or not.

The current "writable pagetables" code for PV guests emulates the
write and validates the resulting PTE.  If it passes validation, it
updates it, without ever making the page actually writable to the
guest itself.

The code is in xen/arch/x86/mm.c, as ptwr_*



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