HVM Migration of domU on Qemu-upstream DM loses ACPI data in xenstore

[Diana Crisan <dcrisan@flexiant.com>]

This is problem 2 of 3 problems we are having with live migration and/or ACPI on Xen-4.3 and Xen-4.2.

Any help would be appreciated.

Detailed description of problem:

We are using Xen-4.3-rc1 with dom0 running Ubuntu Precise and 3.5.0-23-generic kernel, and domU running Ubuntu Precise (12.04) cloud images running 3.2.0-39-virtual. We are using the xl.conf below on qemu-upstream-dm and HVM and two identical sending and receiving machines (hardware and software)

When live migration is instigated between two identical hardware configurations using 'xl migrate', the migrate completes but the xenstore entries on the sending and receiving side differ. 

Prior to issuing a migration the lines 'platform = ""', 'acpi = "1"', 'acpi_s3 = "1"' and 'acpi_s4 = "1"' are present in xenstore (despite the fact xl.conf does not explicitly specify them). However, after the migration succeeds on the receiving side, those lines are missing. 

This is replicable every time.

How to replicate:

1. Take two machines with identical hardware and software, running the xen-4.3-rc1 version of Xen on Ubuntu Precise with 3.5.0-23-generic kernel.
2. Use the xl.conf below as a configuration file.
3. Create a VM using Ubuntu Precise and 3.5.0-23 generic.
4. Start the VM
5. Do xenstore-ls and save it to a file for later comparison.
6. xl migrate from one machine to the other
7. wait until it resumes on the receiving side
8. Do xenstore-ls on the receiving side and save it to a file.
9. Compare the two files and notice that the lines referring to the platform ACPI configuration in xenstore are missing. 

Expected results:

The platform ACPI details should be present in xenstore after a migration.

Actual results:

The platform ACPI details are missing in xenstore after a migration.

Notes:

On xen-4.2, a similar thing happens.

--xl.conf--

builder='hvm'
memory = 512
name = "416-vm"
vcpus=1
disk = [ 'tap:qcow2:/root/diana.qcow2,xvda,w' ]
vif = ['mac=00:16:3f:1d:6a:c0, bridge=defaultbr']
sdl=0
opengl=1
vnc=1
vnclisten="0.0.0.0"
vncdisplay=0
vncunused=0
vncpasswd='p'
stdvga=0
serial='pty'