Nested Virtualisation and UEFI

[James Dingwall <james-xen@dingwall.me.uk>]

Hi,

I am trying to get a nested virtualisation environment working where it is started with bios='ovmf'.  When my 
hvm configuration is bios='seabios' and I use the xen.gz everything starts correctly.  Using the xen.efi from 
the same build when bios='ovmf' causesthe guest Linux kernel to block when accessing the emulated disk 
controller (scsi or ide) as below.

Is this nested configuration expected to work?  If so, are there other things that need to change apart from 
switching the bios configuration value?  I can provide more information from the guest XEN / kernel logs or the 
guest configuration file if that would be useful.

[   31.848214] ata1: lost interrupt (Status 0x50)
[   31.855823] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
[   31.866516] ata1.00: failed command: READ DMA
[   31.873472] ata1.00: cmd c8/00:08:00:00:00/00:00:00:00:00/e0 tag 0 dma 4096 in
[   31.873472]          res 40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
[   31.896759] ata1.00: status: { DRDY }
[   31.902526] ata1: soft resetting link
[   32.076309] ata1.00: configured for MWDMA2
[   32.083559] ata1.00: device reported invalid CHS sector 0
[   32.094014] ata1: EH complete

I am using some backported builds for Ubuntu 14.04:

dom0 (BIOS boot):
ovmf_0~20150106.5c2d456b-1build1_all.deb
qemu-system-x86_2.2+dfsg-5expubuntu9_amd64.deb
xen-hypervisor-4.5-amd64_4.5.0-1ubuntu4_amd64.deb
linux-image-generic-lts-vivid 3.19.0-26-generic

domU:
xen-4.4.3 (custom build from git release tag, also tried xen-4.5.1.efi with same behaviour)
linux-image-generic-lts-vivid 3.19.0-27-generic

Thanks,
James