<div dir="ltr"><div>Hello,</div><div>I find "discard":"unmap" is defaultly enabled in  qemu cmdline(libvirt v6.6, qemu v5.1):</div><div>XML:</div><div><disk type="file" device="disk"><br>      <driver name="qemu" type="qcow2"/><br>      <source file="/var/lib/libvirt/images/new.qcow2" index="2"/><br>      <backingStore/><br>      <target dev="sda" bus="scsi"/><br>      <alias name="scsi0-0-0-0"/><br>      <address type="drive" controller="0" bus="0" target="0" unit="0"/><br>    </disk><disk type="network" device="disk"><br>      <driver name="qemu" type="raw" error_policy="report"/><br>      <source protocol="nbd" name="new" tls="no" index="1"><br>        <host name="localhost" port="10809"/><br>      </source><br>      <target dev="vdb" bus="virtio"/><br>      <alias name="virtio-disk1"/><br>      <address type="pci" domain="0x0000" bus="0x02" slot="0x00" function="0x0"/><br>    </disk></div><div><br></div><div>QEMU cmdline:<br>... -blockdev {"driver":"file","filename":"/var/lib/libvirt/images/new.qcow2","node-name":"libvirt-2-storage","auto-read-only":true,<b>"discard":"unmap"</b>} -blockdev {"node-name":"libvirt-2-format","read-only":false,"driver":"qcow2","file":"libvirt-2-storage","backing":null} -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,device_id=drive-scsi0-0-0-0,drive=libvirt-2-format,id=scsi0-0-0-0,bootindex=1 -blockdev {"driver":"nbd","server":{"type":"inet","host":"localhost","port":"10809"},"export":"new","node-name":"libvirt-1-storage","auto-read-only":true,<b>"discard":"unmap"</b>} -blockdev {"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"} -device virtio-blk-pci,bus=pci.2,addr=0x0,drive=libvirt-1-format,id=virtio-disk1,werror=report,rerror=report ...</div><div><br></div><div>I think it's from <a href="https://gitlab.com/libvirt/libvirt/-/blob/master/src/qemu/qemu_block.c#L1211">https://gitlab.com/libvirt/libvirt/-/blob/master/src/qemu/qemu_block.c#L1211</a></div><div>But I cannot find the reason from commit msgs or documents.</div><div>Could you please explain it?<br></div></div>