Libvirt NVME support

[Peter Krempa]

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.