RE: [Xen-devel] Are linear page tables and writable page tablesincompatible?

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> At the start of day I enable writable page tables - and they 
> work, but only when accessed through a separate mapping. 
> FreeBSD's i386 pmap treats the page tables as an array that 
> is mapped right after userspace. Can writable page tables be 
> made to work in this context?

Interesting point, I don't think anyone's ever thought about this
before.

You'd need to maintain a copy of each L2 in which all the entries are
read only, and have the linear pt map slot point at that: Xen needs to
be able to selectively write enable the entries in writable page table
mode.

Ian


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