Re: [ndctl PATCH 13/15] cxl/region: Default to memdev mode for create with no arguments

[Alison Schofield <alison.schofield@intel.com>]

On Mon, Nov 07, 2022 at 03:48:43PM -0800, Dan Williams wrote:
> Alison Schofield wrote:
> > On Sun, Nov 06, 2022 at 03:48:01PM -0800, Dan Williams wrote:
> > > Allow for:
> > > 
> > >    cxl create-region -d decoderX.Y
> > > 
> > > ...to assume (-m -w $(count of memdevs beneath decoderX.Y))
> > 
> > I'm not understanding what the change is here. Poked around a bit
> > and still didn't get it. Help!
> > 
> > Leaving out the -m leads to this:
> > $ cxl create-region -d decoder3.3 mem0 mem1
> > cxl region: parse_create_options: must specify option for target object types (-m)
> > cxl region: cmd_create_region: created 0 regions
> > 
> > Leaving out the the -m and the memdevs fails because the memdev order is
> > not correct. 
> > $ cxl create-region -d decoder3.3
> > cxl region: create_region: region5: failed to set target0 to mem1
> > cxl region: cmd_create_region: created 0 regions
> > 
> > This still works, where I give the -m and the correct order of memdevs.
> > cxl create-region -m -d decoder3.3 mem0 mem1
> 
> Oh, I was not expecting the lack of automatic memdev sorting to rear its
> head so quickly, and thought that "cxl list" order was good enough for
> most configurations.

I wasn't clear on what was being advertised as supported with this
change. I didn't read this as an announcement of automatic region
creation, but it seemed you were hinting at it.

> 
> Can provide more details on your configuration in this case? If this is
> current cxl_test then I already do not expect it to work with anything
> but decoder3.4 since the other decoders have more complicated ordering
> constraints.
> 
> I.e. your:
> 
> cxl create-region -d decoder3.3
> 
> ...worked as expected in that it found some memdevs to attempt to create
> the region, but you got unlucky in the sense that the default order that
> 'cxl list' returns memdevs was incompatible with creating a region.

Pretty much exactly as you say above. My example was w cxl_test
decoder3.3, w 2 HB's. The automagic worked fine w decoder3.4 w 1 HB.