Reproduced this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.184.el6.x86_64 kernel:2.6.32-198.el6.x86_64 hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64 kernel:2.6.32-71.31.1.el6.x86_64
steps:
1.boot guest with floopy 
  #/usr/libexec/qemu-kvm ...-drive file=/mnt/virtio-driver-1.vfd,if=floppy,format=raw
2.do migrate form hostA to hostB

Results:migrate failed
show the below fail message
qemu: warning: error while loading state for instance 0x0 of device 'ram'
load of migration failed


Veriry this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.190.el6.x86_64
kernel:2.6.32-198.el6.x86_64 hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64 kernel:2.6.32-71.31.1.el6.x86_64 using steps as same as reproduce

Results:show the same error as same as reproduce

Actual results:
migrate successful


Above all,this issue still have problem,there have a bug698936 about the same problem, Maybe this bug should modify first,then this issue will be resolved.Or this is a new bug?thanks~~

(In reply to comment #8)
> Reproduced this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.184.el6.x86_64
> kernel:2.6.32-198.el6.x86_64
> hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64
> kernel:2.6.32-71.31.1.el6.x86_64
> steps:
> 1.boot guest with floopy 
>   #/usr/libexec/qemu-kvm ...-drive
> file=/mnt/virtio-driver-1.vfd,if=floppy,format=raw
> 2.do migrate form hostA to hostB
> 
> Results:migrate failed
> show the below fail message
> qemu: warning: error while loading state for instance 0x0 of device 'ram'
> load of migration failed
> 
> 
> Veriry this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.190.el6.x86_64
> kernel:2.6.32-198.el6.x86_64
> hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64
> kernel:2.6.32-71.31.1.el6.x86_64 using steps as same as reproduce
> 
> Results:show the same error as same as reproduce
> 
> Actual results:
> migrate successful
> 
> 
> Above all,this issue still have problem,there have a bug698936 about the same
> problem, Maybe this bug should modify first,then this issue will be resolved.Or
> this is a new bug?thanks~~

Looks realted, And can you try doing an offline migration to test this bz?
Just stop the machine before doing the migration.
Thanks

Reproduced this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.184.el6.x86_64
kernel:2.6.32-198.el6.x86_64
hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64
kernel:2.6.32-71.31.1.el6.x86_64
steps:
1.boot guest with floopy 
  #/usr/libexec/qemu-kvm ...-drive file=/mnt/virtio-driver-1.vfd,if=none,id=drive-fdc0-0-0,format=raw,cache=none -global isa-fdc.driveA=drive-fdc0-0-0
2.do migrate form hostA to hostB

Results:migrate failed
show the below fail message
qemu-kvm-0.12.1.2-2.184.el6.x86_64
qemu: warning: error while loading state for instance 0x3f0 of device 'fdc'
load of migration failed

Veriry this issue with hostA(rhel6.2):qemu-kvm-0.12.1.2-2.189.el6.x86_64
kernel:2.6.32-198.el6.x86_64
hostB(rhel6.0.z):qemu-kvm-0.12.1.2-2.113.el6.x86_64
kernel:2.6.32-71.31.1.el6.x86_64 using steps as same as reproduce

Results:
migrate successful

Above all,this issue have been fixed.
addtional info:
this kind of migration only support vnc boot guest,not support spice.

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Cause:

In order to save media_changed flag of floppy across migration, a new subsection were introduced, and the subsection were sent when the floppy were not changed ( media_changed is zero ). This would as the subsection would be sent almost every time. 

Consequence:

As qemu-kvm would fail the migration when it met the subsection it does not recongize, this would cause the migration from newer qemu-kvm version to elder version with floppy fail.

Fix:

In order to keep the migration compatibility, the fix only accept the subseciont but do nothing and also disable the sending of the subsection.

Result:

The migration between any version of qemu-kvm with floopy would success.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1531.html