E.g.
virt-install \
... \
--disk /tmp/disk0.qcow2,size=16,driver.type=qcow2,blockio.discard_granularity=4096
It results in the following domain xml:
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' discard='unmap'/>
<source file='/tmp/disk0.qcow2'/>
<target dev='vda' bus='virtio'/>
<blockio discard_granularity="4096"/>
</disk>
Signed-off-by: Lin Ma <lma@suse.de>