On Thu, Feb 23, 2006 at 10:30:39PM -0800, Chen, Kenneth W wrote:
> David Gibson wrote on Thursday, February 23, 2006 8:06 PM
> > But I don't see how not transforming them sometimes can be correct.
> > Suppose 'floor' is only a little way below 'addr' - addr will be
> > shifted down, but floor won't, so floor may now be above addr, which
> > will cause weird results.
> >
> > Afaict the *only* thing floor and ceiling are used for is bounds
> > checking the address range we're examining. How can that ever be
> > right if one address has been scaled down, but the other hasn't.
>
> The scale down isn't exactly on every address bits. Top 3 bits of
> virtual address are preserved.
Ah.. yes.
> #define htlbpage_to_page(x) (((unsigned long) REGION_NUMBER(x) << 61)
> | (REGION_OFFSET(x) >>
> (HPAGE_SHIFT-PAGE_SHIFT)))
>
> So scaled address for a hugetlb address will never be below unscaled
> normal page address. That is adjusted addr will never below unchanged
> floor.
Ok. So in fact it wouldn't matter whether or not addresses outside
the region are scaled, but conceptually they probably should be.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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