xen 4.6 upgrade and non starting Ubuntu guests

[David Brownlee <abs%absd.org@localhost>]

On the offchance that anyone has seen this (or might be able to point
me somewhere - I've had a search around but not been able to find any
pointers)

Just tried updating a netbsd-7/amd64 from xen 4.5 to 4.6. Including
startup scripts and contents of etc/xen (interestingly the new 4.6
etc/xen contents work fine under 4.5)

xencommons gave a "WARNING: Failed to open connection to gnttab" but
appeared to otherwise work.

Interestingly none of the VMs seem to start up (all Ubuntu).

cat jira
# VM 3
name = "jira"
memory = "2500" # 1870 Matches Rackspace '2G' server
disk = [ 'phy:/dev/mapper/vg0-jira,xvda,w' ]
vif = [ 'mac=02:00:00:00:01:03, bridge=bridge0', ]
bootloader = "pygrub"
vcpus = 4

Error to console:

Parsing config from /etc/xen/cfg/jira
libxl: error: libxl_bootloader.c:597:bootloader_copyfail: unexpected
eof copying bootloader output
libxl: error: libxl_create.c:1144:domcreate_rebuild_done: cannot
(re-)build domain: -3
libxl: error: libxl.c:1610:libxl__destroy_domid: non-existant domain 1
libxl: error: libxl.c:1568:domain_destroy_callback: unable to destroy
guest with domid 1
libxl: error: libxl.c:1495:domain_destroy_cb: destruction of domain 1 failed

Content of booloader.*.log

Using <class 'grub.GrubConf.Grub2ConfigFile'> to parse /boot/grub/grub.cfg
WARNING:root:grub2's saved_entry/next_entry not supported
WARNING:root:Unknown directive else
WARNING:root:Unknown directive menuentry_id_option
WARNING:root:Unknown directive else
WARNING:root:Unknown directive menuentry_id_option
[...]
WARNING:root:Unknown directive source
ESC(BESC)0ESC[1;24rESC[m^OESC[?7hESC[?1hESC=ESC[HESC[JESC[?1hESC=
    pyGRUB  version 0.6
 ESC[0m^Nlqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqk^O
 ESC[0m^Nx^O ESC[0;7m^OUbuntu
                      ESC[m^O ESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-88-genericESC[35CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-88-generic (recovery
mode)ESC[19CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-87-genericESC[35CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-87-generic (recovery
mode)ESC[19CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-86-genericESC[35CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-86-generic (recovery
mode)ESC[19CESC[0m^Nx^O
 ESC[0m^Nx^O Ubuntu, with Linux 3.13.0-85-genericESC[35CESC[0m^Nx^O
 ESC[0m^Nmqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqj^O
ESC[70DESC[0m^N^OUse the ESC[0m^N^^O and ESC[0m^Nv^O keys to select
which entry is highlighted.
ESC[58DPress enter to boot the selected OS, 'e' to edit the
ESC[52Dcommands before booting, 'a' to modify the kernel arguments
ESC[59Dbefore booting, or 'c' for a command
line.ESC[5AESC[26CESC[11BESC[68DESC[?1lESC>ESC[24;1H^MESC[?1lESC>