Re: [Qemu-devel] Qemu Shared memory

[Eric Blake <eblake@redhat.com>]

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On 06/30/2014 10:34 AM, Gary Jordan wrote:
> Dear developers,
> 
> I want to design a shared memory for Vm in qemu. So, I also need to design
> a mechanism to let two vms communicate. Is there already some module in
> Qemu ?

It sounds like you are asking about ivshmem, which has already been
discussed a lot lately.  Please search the list archives.

> 
> I saw that qemu could support live migration. Can the vm also access the
> previous machine after migration? Thanks.

I'm not sure what you are asking here.  From the guest's standpoint,
live migration is transparent (the guest should not know that it was
migrated).  Migration is probably unrelated to intra-vm communication,
other than the fact that if you use shared memory to do intra-vm
communication, you have probably rendered your guest unmigrateable.  How
would you communicate between two bare-metal hosts?  The best design is
one in which your guests use the same (emulated) hardware for
intercommunication.  So, if two hosts can effectively communicate via a
network, then using a virtio-net network to communicate between two
guests is the ideal emulation, and also avoids anti-migration lock-in
that you might get if you instead opt for shared memory solutions such
as ivshmem.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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