[dm-devel] [RFC PATCH 3/3] nvme: add the "debug" host driver

[Adam Manzanares]

On Thu, Feb 03, 2022 at 08:52:38AM -0800, Keith Busch wrote:
> On Thu, Feb 03, 2022 at 07:38:43AM -0800, Luis Chamberlain wrote:
> > On Wed, Feb 02, 2022 at 08:00:12AM +0000, Chaitanya Kulkarni wrote:
> > > Mikulas,
> > > 
> > > On 2/1/22 10:33 AM, Mikulas Patocka wrote:
> > > > External email: Use caution opening links or attachments
> > > > 
> > > > 
> > > > This patch adds a new driver "nvme-debug". It uses memory as a backing
> > > > store and it is used to test the copy offload functionality.
> > > > 
> > > > Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
> > > > 
> > > 
> > > 
> > > NVMe Controller specific memory backed features needs to go into
> > > QEMU which are targeted for testing and debugging, just like what
> > > we have done for NVMe ZNS QEMU support and not in kernel.
> > > 
> > > I don't see any special reason to make copy offload an exception.
> > 
> > One can instantiate scsi devices with qemu by using fake scsi devices,
> > but one can also just use scsi_debug to do the same. I see both efforts
> > as desirable, so long as someone mantains this.
> > 
> > For instance, blktests uses scsi_debug for simplicity.
> > 
> > In the end you decide what you want to use.
> 
> Can we use the nvme-loop target instead?

I am advocating for this approach as well. It presentas a virtual nvme
controller already.