Re: [ndctl PATCH v10 0/7] Support poison list retrieval

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

On Wed, Mar 06, 2024 at 03:03:40PM -0800, Dan Williams wrote:
> alison.schofield@ wrote:
> > From: Alison Schofield <alison.schofield@intel.com>
> > 
> > Changes since v9:
> > - Replace the multi-use 'name' var, with multiple descriptive
> >   flavors: memdev_name, region_name, decoder_name (DaveJ)
> > - Use a static string table for poison source lookup (DaveJ)
> > - Rebased on latest pending
> > Link to v9: https://lore.kernel.org/r/cover.1709253898.git.alison.schofield@intel.com/
> > 
> > 
> > Add the option to add a memory devices poison list to the cxl-list
> > json output. Offer the option by memdev and by region. Sample usage:
> > 
> > # cxl list -m mem1 --media-errors
> > [
> >   {
> >     "memdev":"mem1",
> >     "pmem_size":1073741824,
> >     "ram_size":1073741824,
> >     "serial":1,
> >     "numa_node":1,
> >     "host":"cxl_mem.1",
> >     "media_errors":[
> >       {
> >         "dpa":0,
> >         "length":64,
> >         "source":"Internal"
> >       },
> >       {
> >         "decoder":"decoder10.0",
> >         "hpa":1035355557888,
> >         "dpa":1073741824,
> >         "length":64,
> >         "source":"External"
> >       },
> >       {
> >         "decoder":"decoder10.0",
> >         "hpa":1035355566080,
> >         "dpa":1073745920,
> >         "length":64,
> >         "source":"Injected"
> >       }

Dan,

In cleaning up the man pages, I need to follow up on this offset, length
notation.

A default by memdev list now looks like this-

{
 "offset" :
 "length" :
 "source" :
}

Which means dropping the 'decoder' even if it can be discovered from
the trace event. Recall previously a region was listed if present,
then we changed that to a decoder is listed if present.  Now, with
no 'hpa' listing I've dropped the decoder too. That leaves no hint
in the by memdev listing that this poison is in a region. 

Decoders will only be included in the by region list:
{
 "decoder":
 "offset" :
 "length" :
 "source" :
}

OK ?


> >   }
> > ]
> > 
> > # cxl list -r region5 --media-errors
> > [
> >   {
> >     "region":"region5",
> >     "resource":1035355553792,
> >     "size":2147483648,
> >     "type":"pmem",
> >     "interleave_ways":2,
> >     "interleave_granularity":4096,
> >     "decode_state":"commit",
> >     "media_errors":[
> >       {
> >         "decoder":"decoder10.0",
> >         "hpa":1035355557888,
> >         "dpa":1073741824,
> >         "length":64,
> 
> I notice that the ndctl --media-errors records are:
> 
> { offset, length }
> 
> ...it is not clear to me that "dpa" and "hpa" have much meaning to
> userspace by default. Physical address information is privileged, so if
> these records were { offset, length } tuples there is the possibility
> that they can be provided to non-root.
> 
> "Offset" is region relative "hpa" when listing region media errors, and
> "offset" is memdev relative "dpa" while listing memdev relative media
> errors.