Windows 10 HVM suddenly won't create

[cjdl01 <cjdl01@xxxxxxxxxxxxxxxxxx>]

Hello.

I have been using xen for a long time now.  I run it on Debian 9.x  I  
recently performed a routine update, and now my Windows 10 vm will not  
start (HVM), my linux servers stared just fine, however (PV).
I'm getting this error when I try to create the instance:

xl create windows10.cfg
Parsing config from vmsciowin10
Neither kernel nor bootloader specified

Which I suppose is true... a while back (on a previous update), I  
found I had to change my "Kernel =" directive in the config to  
"firmware_override =", so I no longer have a "kernel =" directive.  
Naturally, I tried adding it, or changing my firmware_override back to  
kernel, but it just give me a different error:
xc: error: panic: xc_dom_core.c:702: xc_dom_find_loader: no loader  
found: Invalid kernel
libxl: error: libxl_dom.c:638:libxl__build_dom: xc_dom_parse_image  
failed: No such file or directory
libxl: error: libxl_create.c:1223:domcreate_rebuild_done: cannot  
(re-)build domain: -3
libxl: error: libxl.c:1575:libxl__destroy_domid: non-existant domain 8
libxl: error: libxl.c:1534:domain_destroy_callback: unable to destroy  
guest with domid 8
libxl: error: libxl.c:1463:domain_destroy_cb: destruction of domain 8 failed

I have changed nothing on this virtual machine's config in years.  It  
has started just fine during that time (until today).
The files that were updated today are:
apt
apt-utils
base-files
bind9-host
ca-certificates
dbus
debian-archive-keyring
discover
dpkg
e2fslibs
e2fsprogs
file
gettext-base
gnupg
gnupg-agent
gpgv
grub-common
grub-pc
grub-pc-bin
grub-xen-bin
grub-xen-host
grub2-common
hdparm
libapt-inst2.0
libapt-pkg5.0
libarchive13
libbind9-140
libbluetooth3
libbrlapi0.6
libc-bin
libc-l10n
libc6
libcaca0
libcomerr2
libcurl3-gnutls
libdbus-1-3
libdiscover2
libdns-export162
libdns162
libexpat1
libfreetype6
libfuse2
libgcrypt20
libglib2.0-0
libglib2.0-data
libgnutls30
libicu57
libidn11
libisc-export160
libisc160
libisccc140
libisccfg140
libjpeg62-turbo
libldap-2.4-2
libldap-common
liblwres141
libmagic-mgc
libmagic1
libnghttp2-14
libpam-systemd
libperl5.24
libpng16-16
libprocps6
libpython2.7-minimal
libpython2.7-stdlib
libpython3.5-minimal
libpython3.5-stdlib
libsasl2-2
libsasl2-modules
libsasl2-modules-db
libseccomp2
libspice-server1
libss2
libssh2-1
libssl1.0.2
libssl1.1
libsystemd0
libtimedate-perl
libudev1
libx11-6
libx11-data
libx11-xcb1
libxapian30
libxen-4.8
libxenstore3.0
linux-image-amd64
locales
multiarch-support
openssh-client
openssh-server
openssh-sftp-server
openssl
perl
perl-base
perl-modules-5.24
procps
python-apt-common
python2.7
python2.7-minimal
python3-apt
python3-reportbug
python3.5
python3.5-minimal
qemu-system-common
qemu-system-x86
qemu-utils
reportbug
shared-mime-info
systemd
systemd-sysv
tzdata
udev
usbutils
vim
vim-common
vim-runtime
vim-tiny
wget
xen-hypervisor-4.8-amd64
xen-system-amd64
xen-utils-4.8
xen-utils-common
xenstore-utils
xtightvncviewer
xxd
firmware-linux-free
irqbalance
linux-image-4.9.0-13-amd64

And Finally, my configuration for my windows 10 machine is as follows:
name = "Windows10"
kernel = "/usr/lib/xen-4.8/boot/hvmloader"
#firmware_override = "/usr/lib/xen-4.8/boot/hvmloader"
type='hvm'
memory = 8192
maxmem = 8192
pae = '1'
acpi = '1'
apic = '1'
viridian = '1'
rtc_timeoffset = 0
localtime = '1'
on_poweroff = 'destroy'
on_reboot = 'restart'
on_crash = 'restart'
sdl = '0'
vcpus=4
disk = [ 'phy:/dev/vg1/win10,ioemu:xvda,w' ]
#disk = [ 'phy:/dev/vg1/win10,ioemu:xvda,w','phy:/dev/cdrom,xvdc:cdrom,r' ]
vif = [ "mac=00:16:3E:99:99:99,bridge=xenbr0,model=e1000" ]
acpi = 1
boot="d"
sdl=0
serial='pty'
vnc=1
vnclisten=""
usbdevice = 'tablet'

I have checked, and /usr/lib/xen-4.8/boot/hvmloader absolutely exists  
on the system.
I'm thinking something must have changed regarding syntax... but I've  
been searching for hours, and I cannot find anything that references  
this... can someone please shed some light on this?
Thank you very much for your help!

-Chris