RE: Libvirt NVME support

On Mon, Nov 23, 2020 at 13:07:51 +0000, Thanos Makatos wrote: > > > On Mon, Nov 23, 2020 at 09:47:23 +0000, Thanos Makatos wrote: > > > > On Thu, Nov 19, 2020 at 10:17:56 +0000, Thanos Makatos wrote: > > > > > > 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'/> > > > > > > > > > > 'target dev' is how the device appears in the guest, right? It should be > > > > > something like 'nvme0n1'. I'm not sure though this is something that > > we > > > > can > > > > > put here anyway, I think the guest driver can number controllers > > arbitrarily. > > > > > > > > Well, it was supposed to be like that but really is not. Even with other > > > > buses the kernel can name the device arbitrarily, so it doesn't really > > > > matter. > > > > > > > > > Maybe we should specify something like BDF? Or is this something > > QEMU > > > > will > > > > > have to figure out how to do? > > > > > > > > > > > <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> > > > > > > Revistiting your initial suggestion, it should be something like this > > > (s/sdb/nvme0): > > > > > > <disk type='file' device='disk'> > > > <source dev='/Host/QEMUGuest2.qcow2'/> > > > <target dev='nvme0' bus='nvme'/> > > > <address type='drive' controller='1' bus='0' target='0' unit='1'/> > > > </disk> > > > > Note that the parser for 'dev' is a bit quirky, old, and used in many > > places besides the qemu driver. It's also used with numbers in non-qemu > > cases. Extending that to parse numbers for nvme but not for sda might > > become ugly very quickly. Sticking with a letter at the end ('nvmea' > > might be a more straightforward approach. > > Then I think we should just stick with 'nvme'. You still need a way to "index" it somehow. The target must be unique for each disk.