Re: Libvirt NVME support

> -----Original Message----- > From: Peter Krempa <pkrempa(a)redhat.com&gt; > Sent: 23 November 2020 16:56 > To: Thanos Makatos <thanos.makatos(a)nutanix.com&gt; > Cc: Suraj Kasi <suraj.kasi(a)nutanix.com>; libvirt-list(a)redhat.com; John Levon > <john.levon(a)nutanix.com&gt; > Subject: Re: Libvirt NVME support > > On Mon, Nov 23, 2020 at 16:48:55 +0000, Thanos Makatos wrote: > > > 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: > > > > > > > > > > > > > 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. > > > > I think I've misunderstood something, I thought controller='1' in <address > ...> > > refers to index='1' in <controller ...>. So <address ...> should be: > > > > <address type='nvme' index='1' controller='1' ns='2'/> > > > > What's controller='1' then? > > What I meant by the above is that the value of "<target dev='THIS'" must > be unique for every <disk>. I also wanted to advice to not use numbers > for making it unique. Numbers used for it have a legacy meaning. > > Your suggested <address type='nvme' design looks good. OK, so we definitely need dev='...' in target which is something like [a-zA-Z]+ and is unique. If this identifier is not controlled by the user, I think it would be best not to prefix it with 'nvme' (thus resulting in strings like 'nvmea' or 'nvmeabc'), as they can be rather confusing for people who don't know the details. However, I still don't understand how index='1' and controller='1' in address relate to index='1' in controller: <address type='nvme' index='1' controller='1' ns='2'/>

and <controller type='nvme' index='1' model='nvme'>