virsh qemu-monitor-command block_resize not working

[Daniel P. Berrangé]

On Wed, Jul 14, 2021 at 10:10:35AM +0200, arjen-libvirt at gugu.be wrote:
> Hi List,
> 
> some version info:
> ]# /usr/libexec/qemu-kvm -version
> QEMU emulator version 4.2.0
> (qemu-kvm-4.2.0-48.module+el8.4.0+534+4680a14e) Copyright (c) 2003-2019
> Fabrice Bellard and the QEMU Project developers
> 
> ]# virsh version
> Compiled against library: libvirt 6.0.0
> Using library: libvirt 6.0.0
> Using API: QEMU 6.0.0
> Running hypervisor: QEMU 4.2.0
> 
> information about block devices for one specific guest:
> ]# virsh qemu-monitor-command uat-win201202.uat.gugu.be --hmp info block
> libvirt-2-format:
> /data/kvm/storage/diskimages01/uat-win201202_disk1_C.qcow2 (qcow2)
> Attached to:      /machine/peripheral/virtio-disk0/virtio-backend Cache
> mode:       writeback
> 
> ide0-0-0: [not inserted]
>     Attached to:      ide0-0-0
>     Removable device: not locked, tray closed
> 
> 
> But then, when I want to resize the block device, I just cannot seem to
> find the correct device. I tried all of these:
> 
> virsh qemu-monitor-command uat-win201202.uat.gugu.be --hmp block_resize
> libvirt-2-storage 48G
> Error: Cannot find device=libvirt-2-storage nor node_name=
> 
> virsh qemu-monitor-command uat-win201202.uat.gugu.be --hmp block_resize
> drive-libvirt-2-storage 48G
> Error: Cannot find device=drive-libvirt-2-storage nor node_name=
> 
> virsh qemu-monitor-command uat-win201202.uat.gugu.be --hmp block_resize
> virtio-disk0 48G
> Error: Cannot find device=virtio-disk0 nor node_name=
> 
> virsh qemu-monitor-command uat-win201202.uat.gugu.be --hmp block_resize
> drive-virtio-disk0 48G
> Error: Cannot find device=drive-virtio-disk0 nor node_name=
> 
> In a previous qemu version this worked (EL 7). Can someone help me out?

Libvirt has changed the way it configures disks with QEMU to use the
modern -blockdev argument. I expect this impacts your usage, but I
dont know what the correct naming should be.

Ignoring that though, why are you even using qemu-monitor-command in
the first place ?  Libvirt directly supports live block resizing
via the 'virsh blockresize' command


Regards,
Daniel
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