[Bug 233895] 12.0-RC2: Repeated double fault on AWS r4.large

[b***@freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233895

Bug ID: 233895
Summary: 12.0-RC2: Repeated double fault on AWS r4.large
Product: Base System
Version: 12.0-RELEASE
Hardware: amd64
OS: Any
Status: New
Severity: Affects Many People
Priority: ---
Component: kern
Assignee: ***@FreeBSD.org
Reporter: ***@ofWilsonCreek.com

Created attachment 199989
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=199989&action=edit
Screenshot of panic.

I'm testing 12.0-RC2 on AWS, and getting double-fault panics. We've observed it
at least 3 times, with a stop/start between each, and on two hosts (the only
hosts we have on 12). A stop/start should move it to new host hardware,
eliminating the plausibility of bad hardware. The last release that has been
stable for us is 11.1. (11.2 did not work on AWS due to the crash bug in ena.)
This happens on an r4.large instance (r4.large is large enough to use the ena
NIC driver rather than xn, fwiw).

Screenshot from AWS attached.