Nothing changes during the migration for the VM. This often causes problems if the VM is referring to any fixed external assets (such as host/physical storage through fixed hard-coded paths, network paths etc.), unless taken enough care. For all practical purposes (of migration), you an consider VM just like a real/physical machine (in the sense that moving a physical machine doesn't change any attribute of the machine itself).

http://gk.palem.in

Dear sir, I am thankful for your response. If you kindly provide any reference from research articles, it will be highly appreciated. Thanks a lot. 

This could be a good starting point: Clark, Christopher, et al. "Live migration of virtual machines." Proceedings of the 2nd conference on Symposium on Networked Systems Design & Implementation-Volume 2. USENIX Association, 2005.

From a more practical stand-point, this and related articles could help: http://www.vmware.com/products/vsphere/features/vmotion 

https://www.usenix.org/legacy/event/nsdi05/tech/full_papers/clark/clark_html/

Thank you very much dear Palem. Now it is much clearer that during live migration of VM OS, Apps etc remain same. But, what happens if VM gets restarted? After getting restarted, VM will be booted on new physical host. At this point will boot time components of VM such as BIOS, loader etc will be changed or remain same?

I am very thankful for your help. 

VM essentially is a BlackBox to the host (so to speak). For all practical purposes, the BIOS of VM is different from the BIOS of the physical host. 

The whole guest VM runs inside a "single process" on the host PC. So, the BIOS of guest VM is just another application level parameter to the host PC. (There are bare-metal virtualizations avialable, but similar principle applies there)

VM's BIOS does not get affected by the physical host's BIOS. For example, there is nothing that is stopping you to run an ARM processor in VM inside an x86 processor with different BIOS settings. VM-Player just "emulates" the BIOS settings configured inside the VM.

Having said that, however, the physical machine should have VT capabilities to "emulate" the bios settings of the guest VM. On the physical machines, there is a setting in BIOS such as "enable virtualization", which controls this.

VT-x and AMD-v are the virutalization technologies that work on the bare-metal hardware. They need to be enabled on the physical machine to let VMs run in good condition. The 'virtual processor' inside VM do not have this VTx / AMD-v capabilities - one of the reasons why you cannot run VM inside another VM. 

So, in essense, to answer your question: the BIOS settings, loader etc. nothing changes in the VM. Think of the VM as a file (VM Disk). Once you move any file to another machine, the content of the file will not change - same case here.

Hope this helps.

Thank you,

GK

http://www.sysprobs.com/disable-enable-virtualization-technology-bios

http://gk.palem.in

I am not sure if you are interested in this since it is - in most cases - not a "core component"; and you were looking for core components in your questions

But there is a component that is not migratable without special precautionary measure: the vTPM which stands for virtual Trusted Platform Module.

If you are further interested in this let me know I can give you more details; For the moment I just give you some links/papers on the issue:

www.syssec.ethz.ch/research/vm-vtpm-migration.pdf

Xinlong Liang; Rui Jiang; Huafeng Kong, "Secure and reliable VM-vTPM migration in private cloud," Instrumentation and Measurement, Sensor Network and Automation (IMSNA), 2013 2nd International Symposium on

My paper is not about VM migration in particular but you can use it as an introduction to TPM if you like:

Conference Paper Retaining Control Over Private Virtual Machines Hosted by a ...

You might wanna take a look at this publication... We tested the what happens within a virtual machine when migrated.

Conference Paper TIOSA: Testing VM Interoperability at an OS and Application ...