MFC r268979:

Don't save entropy inside jails.

As of r126744, we no longer feed the entropy device in jails upon
start, and collecting them is no longer useful.

PR:		conf/126744
Submitted by:	Eugene Grosbein <eugen grosbein net> (with minor changes)
Approved by:	so (des)
MFC: r269050 (partial)

Copying and zeroing pages via temporary mappings involves updating the
corresponding page tables followed by accesses to the pages in question.
This sequence is subject to the situation exactly described in the "AMD64
Architecture Programmer's Manual Volume 2: System Programming" rev. 3.23,
"7.3.1 Special Coherency Considerations" [1, p. 171 f.]. Therefore, issuing
the INVLPG right after modifying the PTE bits is crucial.
For pmap_copy_page(), this has been broken in r124956.

1: http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2012/10/24593_APM_v21.pdf

Reviewed by:	alc, kib
Sponsored by:	Bally Wulff Games & Entertainment GmbH
MFC r269127:
Fix for division by zero.
MFC r268929:
Add new device ID.

PR:		191959