Re: [Xen-devel] understanding __linear_l2_table and friends

[Gerd Knorr <kraxel@xxxxxxxxxxx>]

On Wed, Apr 20, 2005 at 07:53:00PM +0100, Ian Pratt wrote:
> > Gerd is correct that it does not fully work for PAE, but not 
> > simply because of address-space considerations.

Well, sort of.  The trick requires that the linear page table address
space is aligned to what the topmost page table level can handle.  And
it eats one entry.  We would have to align the linear page table @ 3GB
and waste 1GB address space, then the self-referencing trick would work
even with the 3rd level I think.  Obviously not an option ;)

> We have to take 4 slots in the L2 handling the top of the VA space, and
> have the four slots point at the 4 L2s. We can use this to access all
> the L1's and L2's.

That's exactly what I'm doing at the moment.

> We then take another slot in the uppermost L2 and have it point at the
> L3.

That I don't ;)

While I'm at it:  Which levels writable pagetables are used for
(without shadowing)?  Only the first?  Or also the other ones?

  Gerd

-- 
#define printk(args...) fprintf(stderr, ## args)

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