Re: Libvirt NVME support

On Wed, Nov 18, 2020 at 09:57:14 +0000, Thanos Makatos wrote: > > As a separate question, is there any performance benefit of emulating a > > NVMe controller compared to e.g. virtio-scsi? > > We haven't measured that yet; I would expect it to be slight faster and/or more > CPU efficient but wouldn't be surprised if it isn't. The main benefit of using > NVMe is that we don't have to install VirtIO drivers in the guest. Okay, I'm not sold on the drivers bit but that is definitely not a problem in regards of adding support for emulating NVME controllers to libvirt. As a starting point a trivial way to model this in the XML will be: <controller type='nvme' index='1' model='nvme'> And then add the storage into it as: <disk type='file' device='disk'> <source dev='/Host/QEMUGuest1.qcow2'/> <target dev='sda' bus='nvme'/> <address type='drive' controller='1' bus='0' target='0' unit='0'/> </disk> <disk type='file' device='disk'> <source dev='/Host/QEMUGuest2.qcow2'/> <target dev='sdb' bus='nvme'/> <address type='drive' controller='1' bus='0' target='0' unit='1'/> </disk> The 'drive' address here maps the disk to the controller. This example uses unit= as the way to specify the namespace ID. Both 'bus' and 'target' must be 0.