K 10
svn:author
V 5
sephe
K 8
svn:date
V 27
2016-02-05T05:31:31.442259Z
K 7
svn:log
V 426
hyperv/hn: Recover half of the chimney sending space

We lost half of the chimney sending space, because we mis-used
ffs() on a 64 bits mask, where ffsl() should be used.

While I'm here:
- Use system atomic operation instead.
- Stringent chimney sending index assertion.

Reviewed by:	adrian
Approved by:	adrian (mentor)
MFC after:	1 week
Sponsored by:	Microsoft OSTC
Differential Revision:	https://reviews.freebsd.org/D5159

END