linux-kernel - Re: [PATCH 09/26] cxl/region: Add Dynamic Capacity CXL region support

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Date: Tue, 9 Apr 2024 21:40:33 -0700
From: Ira Weiny <ira.weiny@...el.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>, <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>, "Navneet
 Singh" <navneet.singh@...el.com>, Dan Williams <dan.j.williams@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>, Alison Schofield
	<alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>,
	<linux-btrfs@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/26] cxl/region: Add Dynamic Capacity CXL region support

Jonathan Cameron wrote:
> On Sun, 24 Mar 2024 16:18:12 -0700
> ira.weiny@...el.com wrote:
> 
> > From: Navneet Singh <navneet.singh@...el.com>
> > 
> > CXL devices optionally support dynamic capacity.  CXL Regions must be
> > configured correctly to access this capacity.  Similar to ram and pmem
> > partitions, DC Regions, as they are called in CXL 3.1, represent
> > different partitions of the DPA space.
> > 
> > Introduce the concept of a sparse DAX region.  Add the create_dc_region
> > sysfs entry to create sparse DC DAX regions.  Special case DC capable
> > regions to create a 0 sized seed DAX device to maintain backards
> > compatibility with older software which needs a default DAX device to
> > hold the region reference.
> > 
> > Flag sparse DAX regions to indicate 0 capacity available until such time
> > as DC capacity is added.
> > 
> > Interleaving is deferred in this series.  Add an early check.
> > 
> > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> With the -EBUSY others addressed LGTM.

But the other docs do not have that notation.  Also the EBUSY was not changed
from the previous documentation.  Only the text for DC was added.

I'm inclined to leave this.

> Fan's duplication comment
> might be something to tidy up later.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>

Thanks,
Ira