repeatable panic on pageout with 945GM

[Konstantin Belousov]

On Sat, Jun 04, 2016 at 02:59:01PM -0400, Michael Butler wrote:
> On 06/04/16 13:47, Konstantin Belousov wrote:
> 
>  [ .. snip .. ]
> 
> > I believe that this is a bug in amd64 pmap. Fictitious pages are not
> > promoted, in particular, the pv_table array does not span over the
> > dynamically registered fictitious ranges. As result, pa_to_pvh() returns
> > garbage and pvh must not be accessed in the case of 'small_mappings' in
> > several pmap functions.  It is typically not accessed, except in case
> > when we have to drop and reacquire pv lock, to avoid LOR with pmap.
> > 
> > i386 does not have the issue, due to pvh_global_lock.
> > 
> > Below is the supposed fix (not tested).
> 
>  [ .. snip .. ]
> 
> Is this something I should test and, should it not introduce any other
> issues, might get committed?

Would be nice to test.  I expect that this patch is going to be committed,
after the review.