Re: [Qemu-devel] cpuid problem in upstream qemu with kvm

[Avi Kivity]

On 01/07/2010 02:33 PM, Anthony Liguori wrote:
> There's another option.
>
> Make cpuid information part of live migration protocol, and then 
> support something like -cpu Xeon-3550.  We would remember the exact 
> cpuid mask we present to the guest and then we could validate that we 
> can obtain the same mask on the destination.

Currently, our policy is to only migrate dynamic (from the guest's point 
of view) state, and specify static state on the command line [1].

I think your suggestion makes a lot of sense, but I'd like to expand it 
to move all guest state, whether dynamic or static.  So '-m 1G' would be 
migrated as well (but not -mem-path).  Similarly, in -drive 
file=...,if=ide,index=1, everything but file=... would be migrated.

This has an advantage wrt hotplug: since qemu is responsible for 
migrating all guest visible information, the migrator is no longer 
responsible for replaying hotplug events in the exact sequence they 
happened.

In short, I think we should apply your suggestion as broadly as possible.

[1] cpuid state is actually dynamic; repeated cpuid instruction 
execution with the same operands can return different results.  kvm 
supports querying and setting this state.

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