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

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Date: Thu, 4 Apr 2024 11:26:28 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: <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

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 backwards
> 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.  Fan's duplication comment
might be something to tidy up later.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>