The Monitor menu in a KVM is an interface used to interact with a running KVM virtual machine directly through the QEMU Monitor Protocol (QMP). We can initiate monitor commands through the Proxmox monitor interface and see the result on the same page. There are a large number of commands used to perform various tasks through the Monitor menu. For example, in the following screenshot, we've entered the info pci command to view the PCI devices that the VM sees at this moment:

The monitor is a great way to debug a KVM VM-related issue due to the ability to gather a vast amount of debugging data, including the memory core dump, CPU info, and so on. We can also inject configurations, such as balloon memory configuration, additional CPUs, and USB devices through this Monitor menu into a running KVM VM. Type help to view a list of all the commands usable with Monitor.