Re: [PATCH] VMI: remove CONFIG_DEBUG_PAGE_TYPE and associated bitrotted code

[Chris Wright <chrisw@sous-sol.org>]

* Jeremy Fitzhardinge (jeremy@goop.org) wrote:
> Zachary Amsden wrote:
> >I'd rather keep it, even with bitrot - it was non-trivial to get 
> >correct, and found many surprises in the code; most notably, it can 
> >detect
> >
> >1) PTE writes to pages not declared as page tables
> >2) Failure to allocate or de-allocate page tables using the 
> >paravirt-ops API
> >3) PTE writes using the wrong level operations
> >
> >These are most useful properties; in fact, I would like to extend the 
> >code for 64-bit paravirt-ops and 4-level paging, so rather not kill it 
> >until then.
> >
> >I never merged the whole bit upstream because it added a field to 
> >struct page. 
> 
> Hm, is that a big problem?  It would be OK for a debug config option, 
> wouldn't it?  Also, it doesn't seem particularly vmi-specific.  Could it 
> be made part of the pvops infrastructure?

I'm pretty sure lguest64 hit some of the problems Zach is trying to
catch, so should generalize well-enough.

thanks,
-chris