[coreboot] kexec of Xen hypervisor from a Linux payload

[Trammell Hudson]

On Mon, Jul 25, 2016 at 01:27:22PM -0600, Trammell Hudson wrote:
> I did find this note from 2008 that mentioned a similar
> issue regarding xen, kexec and coreboot:
> 
> http://ward.vandewege.net/blog/2008/08/kexecing-into-a-xen-kernel/

Following the links to the xen-devel mailing list had some hints:

# There seems to be a regression with regard to kexec'ing into
# a Xen kernel between Xen 3.1.0 (confirmed working) and 3.1.3
# (confirmed not working). I would try 3.1.1 and 3.1.2 but
# source for 3.1 versions older than 3.1.3 no longer seems to
# be available for download. I still had source for 3.1.0
# lying around, luckily.

I decided to try Xen 3.1.0 and found that the hypervisor
does start up just fine when kexec'ed from my Linux payload
launched from Coreboot (although my 4.6 payload isn't
compatible with the ELF loader used by the older Xen):

https://www.flickr.com/photos/osr/27931937284/in/photostream/lightbox/

Ward's further testing was the Xen 3.2 tree would fail to kexec
even with the "no-real-mode" flag and came to the conclusion that:

# This is likely a coreboot bug, so I'll have to track that
# down. Any information about differences between what 3.2.1
# and 3.1.4 require to be kexec'ed into would be most helpful
# though.

Unfortunately there weren't any followups.

-- 
Trammell