Re: how set_pte_at()'s vaddr and ptep args relate

[Jeremy Fitzhardinge <jeremy@goop.org>]

Zachary Amsden wrote:
> "Who can discern his errors?  Forgive my hidden faults."
In general that Book doesn't give much in the way of architectural 
certainty.  3.12 IA32SDM isn't much better:

    Whenever a page-directory or page-table entry is changed (including
    when the present flag is set to zero), the operating-system must
    immediately invalidate the corresponding entry in the TLB so that it
    can be updated the next time the entry is referenced.

The parenthetic clause is annoyingly ambiguous: does it mean "when the 
present flag is currently set to 0" or "when setting the present flag to 
0"?  The passive voice should always be avoided.


> Oh, wow.  Unfortunately, the complexity isn't from how frequent or 
> rare a kmapped PT access is, it is from it being there at all.

We'll see how it works out.  What actually needs to do cross-process 
pagetable manipulation?  Fork?  ptrace?

    J