[Qemu-discuss] Difference between qemu-kvm, qemu-system-x86_64, qemu-x86_64

[Zhang Qiang]

For new features, I recently updated qemu-kvm 1.5.3 to qemu 2.5.0, but I saw several qemu binaries, `/usr/local/bin/qemu-x86_64` and `/usr/local/bin/qemu-system-x86_64`. It seems `qemu-system-x86_64` is the emulator program, since libvirt won't recognize `qemu-x86_64`. Then what's qemu-x86_64 for?

And according to this qemu doc: http://wiki.qemu.org/KVM:

> qemu-kvm fork for x86 (deprecated, use upstream QEMU now)

It seems qemu is replacing qemu-kvm. But if qemu not qemu-kvm is used, is the guest CPU still provided by KVM? If not so, will the performance be worse?