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1.5.4. Access Qemu Monitor via libvirt

The Qemu Monitor11 is the way to interact with qemu/KVM while a guest is running. This interface has many and very powerful features for experienced users. When running under libvirt that monitor interface is bound by libvirt itself for management purposes, but a user can run qemu monitor commands via libvirt still. The general syntax is virsh qemu-monitor-command [options] [guest] 'command'

Libvirt covers most use cases needed, but if you every want/need to work around libvirt or want to tweak very special options you can e.g. add a device that way:

virsh qemu-monitor-command --hmp zesty-test-log 'drive_add 0 if=none,file=/var/lib/libvirt/ images/test.img,format=raw,id=disk1'

But since the monitor is so powerful, you can do a lot especially for debugging purposes like showing the guest registers:

virsh qemu-monitor-command --hmp y-ipns 'info registers'

RAX=00ffffc000000000 RBX=ffff8f0f5d5c7e48 RCX=0000000000000000 RDX=ffffea00007571c0

RSI=0000000000000000 RDI=ffff8f0fdd5c7e48 RBP=ffff8f0f5d5c7e18 RSP=ffff8f0f5d5c7df8 [...]

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