GSoC

Here is the latest from Xen UEFI land:

• We can boot to UEFI Shell, finally. The hurdles were -
• Different PCI I/O range compared to Qemu, this resulted in a domain crash when an emulated I/O device tried to register for already registered ports. Boo.
• ACPI timer block hardcoded by Xen at I/O 0xB000. Yes, modifying the "special BAR" has no effect, so UEFI TimerLib code needs to be careful in configuring the timer... if the PCI registers already look configured - use selected values. They are now set once in hvmloader.
• 8259 PIC ExtInt routing needed to be enabled in APIC inside hvmloader, because TianoCore has no APIC support.
• Started making OvmfPkg Xen aware. This was necessarily for at least registering the right I/O ranges. Now, the hypercall pages are populated and a GUIDed HOB containing Xen hypervisor info is published. This will be consumed by the hypervisor DXE.

I see the overall layering as being something like -

• Hypervisor driver - consumes HOB, publishes the EFI_XEN_HYPERCALL_PROTOCOL.
• XenTables driver - exposes Xen ACPI and SMBIOS tables, which were built into hvmloader.
• XenBus driver - consumes Hypervisor driver, creates child nodes for virtual I/O devices, publishes EFI_XEN_BUS_PROTOCOL.
• XenStore driver - exercises XenBus interface, allows SIMPLE_FILE_IO_PROTOCOL access to XenStore nodes.
• Blockfront, Netfront, Fbfront drivers for block, network and video, respectively.

Latest patches as usual at https://github.com/andreiw/andreiw-wip/tree/master/xen/ovmf-support.

UEFI OVMF/Xen

For anyone interested in the GSoC project status:
- We can boot the 32-bit and the 64-bit OVMF image now inside an HVM domain instead of BIOS
- We end up crashing the HVM domain during PCI bus enumeration (qemu-dm crash?), which is what the student is now investigating...

Xen changes so far included refactoring changes inside hvmloader, adding a new bios_config structure for OVMF images, ensuring that guest physical memory under 4GB is backed with pages, as well as moving out Xen structures from below 4GB where they would collide with the firmware. The hvmloader/bios xenstore key was exposed to xend/xm (hvmbios parameter, values can be rombios, ovmf32 and ovmf64), to faciliate easier testing. Some thought still needs to be put into libxl (xend replacement) changes.
In general OVMF/Xen patches for Xen and TianoCore will be at https://github.com/andreiw/andreiw-wip/tree/master/xen/ovmf-support

GSoC

Today Jordan Justen of the EDK2 TianoCore project announced that four students will be working on UEFI EDK2 projects. I am very excited to be mentoring the OVMF on Xen project, which will enable UEFI firmware for HVM Xen virtual machines.

With luck and lots and lots of work, by the end of this mentorship we will be able to boot into Linux using Xen PV devices (blkback...).

This presents a wonderful opportunity to share my Xen and EDK experiences and help out two projects I love :-).