To enable scsi in qemu/kvm, please use:
<qemu-system-x86_64 or kvm>  -drive index=0,media=disk,if=scsi,boot=on ...

You need to give boot=on option to the scsi drive for the qemu bios to boot from it.
If you're compiling from sources, please make sure that qemu is compiled from latest sources. The older version of qemu won't support the boot=on argument for -drive options.

Dushyant has installed qemu/kvm at: /usr/bin/qemu-system-x86_64 #  /usr/bin/kvm

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Regards,
Deepak Ravi