Re: [PATCH v7 08/14] nvmet-core: allow one host per passthru-ctrl

[Sagi Grimberg]

> > > > I don't understand why we don't limit a regular ctrl to single 
> > > > access and we do it for the PT ctrl.
> > > >
> > > > I guess the block layer helps to sync between multiple access in 
> > > > parallel but we can do it as well.
> > > >
> > > > Also, let's say you limit the access to this subsystem to 1 user, 
> > > > the bdev is still accessibly for local user and also you can create 
> > > > a different subsystem that will use this device (PT and non-PT ctrl).
> > > >
> > > > Sagi,
> > > >
> > > > can you explain the trouble you meant and how this limitation solve 
> > > > it ?
> > >
> > > Its different to emulate the controller with all its admin
> > > commands vs. passing it through to the nvme device.. (think of format 
> > > nvm)
> > we don't need to support format command for PT ctrl as we don't 
> > support other commands such create_sq/cq.
>
> That is just an example, basically every command that we are not aware
> of we simply passthru to the drive without knowing the implications
> on a multi-host environment..

If we were to change the logic of nvmet_parse_passthru_admin_cmd to
have the default case do nvmet_parse_admin_cmd, and only have
the vendor-specific space opcodes do nvmet_passthru_execute_cmd
then I could not see at the moment how we can break a multi-host
export...