Re: [ndctl PATCH v11 6/7] cxl/list: add --media-errors option to cxl list

[Dan Williams <dan.j.williams@intel.com>]

Alison Schofield wrote:
> On Fri, Mar 15, 2024 at 10:09:44AM +0900, Wonjae Lee wrote:
> > alison.schofield@intel.com wrote:
> > > From: Alison Schofield <alison.schofield@intel.com>
> > >
> > > The --media-errors option to 'cxl list' retrieves poison lists from
> > > memory devices supporting the capability and displays the returned
> > > media_error records in the cxl list json. This option can apply to
> > > memdevs or regions.
> > >
> > > Include media-errors in the -vvv verbose option.
> > >
> > > Example usage in the Documentation/cxl/cxl-list.txt update.
> > >
> > > Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> > > ---
> > > Documentation/cxl/cxl-list.txt 62 +++++++++++++++++++++++++++++++++-
> > > cxl/filter.h                    3 ++
> > > cxl/list.c                      3 ++
> > > 3 files changed, 67 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/cxl/cxl-list.txt b/Documentation/cxl/cxl-list.txt
> > > index 838de4086678..6d3ef92c29e8 100644
> > > --- a/Documentation/cxl/cxl-list.txt
> > > +++ b/Documentation/cxl/cxl-list.txt
> > 
> > [snip]
> > 
> > +----
> > +In the above example, region mappings can be found using:
> > +"cxl list -p mem9 --decoders"
> > +----
> > 
> > Hi, isn't it '-m mem9' instead of -p? FYI, it's also on patch's
> > cover letter, too.
> 
> Thanks for the review! I went with -p because it gives only
> the endpoint decoder while -m gives all the decoders up to
> the root - more than needed to discover the region.

The first thing that comes to mind to list memory devices with their
decoders is:

    cxl list -MD -d endpoint

...however the problem is that endpoint ports connect memdevs to their
parent port, so the above results in:

  Warning: no matching devices found

I think I want to special case "-d endpoint" when both -M and -D are
specified to also imply -E, "endpoint ports". However that also seems to
have a bug at present:

# cxl list -EDM -d endpoint -iu
{
  "endpoint":"endpoint2",
  "host":"mem0",
  "parent_dport":"0000:34:00.0",
  "depth":2
}

That needs to be fixed up to merge:

# cxl list -ED -d endpoint -iu
{
  "endpoint":"endpoint2",
  "host":"mem0",
  "parent_dport":"0000:34:00.0",
  "depth":2,
  "decoders:endpoint2":[
    {
      "decoder":"decoder2.0",
      "interleave_ways":1,
      "state":"disabled"
    }
  ]
}

...and:

# cxl list -EMu
{
  "endpoint":"endpoint2",
  "host":"mem0",
  "parent_dport":"0000:34:00.0",
  "depth":2,
  "memdev":{
    "memdev":"mem0",
    "pmem_size":"512.00 MiB (536.87 MB)",
    "serial":"0",
    "host":"0000:35:00.0"
  }
}

...so that one can get a nice listing of just endpoint ports, their
decoders (with media errors) and their memdevs.

The reason that "cxl list -p mem9 -D" works is subtle because it filters
the endpoint decoders by an endpoint port filter, but I think most users
would expect to not need to enable endpoint-port listings to see their
decoders the natural key to filter endpoint decoders is by memdev.