For those interested, this is the Xen bug they were fixing with the reboots http://xenbits.xen.org/xsa/advisory-108.html -Grant On Wed, Sep 24, 2014 at 8:41 PM, Reed Loden <reed@reedloden.com> wrote:
On Wed, 24 Sep 2014 21:39:39 -0400 Peter Beckman <beckman@angryox.com> wrote:
Likely some sort of potentially serious bug or flaw in EC2 or Xen. AWS Security is really on the ball on such things and do everything they can to make invisible fixes with no customer impact, but sometimes a reboot is required in order to apply the changes necessary to keep customer instances safe from attacks and vulnerabilities.
Rumor mill is that it's XSA-108, embargoed until 2014-10-01 12:00 (http://xenbits.xen.org/xsa/). Just somebody's guess, though, afaik.
~reed