Tianocore / OVMF the Open-source community's project to enable EFI / UEFI for virtual machines. OVMF is integrated into Xen 4.4 release with essential patches upstreamed. However in 4.4 it is not built by default.
To build Xen with OVMF support, you would need to have
--enable-ovmf when running
Then enable EFI for your Xen guest by adding
bios='ovmf' to your
xl.cfg file. See the example below for more information.
One thing to have in mind is Xen supports both its own QEMU fork called qemu-traditional and upstream QEMU called qemu-xen. OVMF only supports the latter. Xen 4.4 has upstream QEMU configured for all HVM guests by default, so it is fine to not specify which QEMU to use in guest config file. But if you have already configured qemu-traditional for your guest you would need to delete / comment out that line.
A typical guest config file looks like below. Nothing fancy, just the "bios=" option is important. Also read the comment in the example for disk specification.
builder = 'hvm' name = 's0-efi' vcpus = 2 memory = 1024 # memory = 6000 vif = ['bridge=xenbr0'] # This is a disk image with EFI guest installed, you can also use live CD if you prefer. # You can either specify xvda or hda, QEMU will start with emulated IDE drive in both cases. # But if you speficy sda then it might not boot as OVMF doesn't have the driver at the moment. disk = [ '/data/s0-efi.qcow2,qcow2,xvda,w' ] on_crash = 'preserve' vnc=1 vnclisten='0.0.0.0' serial='pty' bios='ovmf' # if you don't have this line, seabios will be used
Here we will describe the different ways one can enable the debug output of OVMF.
Log into a file
Simply add the following to your guest config file:
device_model_args_hvm = [ # Debug OVMF '-chardev', 'file,id=debugcon,path=/var/log/xen/ovmf.log,', '-device', 'isa-debugcon,iobase=0x402,chardev=debugcon', ]
This will tell QEMU to save OVMF's debug output to
(Checkout QEMU's help of -chardev for more options.)
Log via the guest console
The alternative is to recompile OVMF so that it would log its debug via the guest console.
Recompile OVMF with
-D DEBUG_ON_SERIAL_PORT to enable the use of the console.
To recompile OVMF,
you can edit
-D DEBUG_ON_SERIAL_PORT to the
OvmfPkg/build.sh command line
before building OVMF via Xen build system.
Or you can execute
OvmfPkg/build.sh -a X64 -b DEBUG -n $(nproc) -D DEBUG_ON_SERIAL_PORT
within the ovmf directory.