linux-kernel - Re: [PATCH RFC v2 08/18] cxl/region: Add Dynamic Capacity CXL region support

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Message-ID: <64f801e098dd2_234994294d0@iweiny-mobl.notmuch>
Date:   Tue, 5 Sep 2023 21:36:48 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Dave Jiang <dave.jiang@...el.com>, Ira Weiny <ira.weiny@...el.com>,
        "Dan Williams" <dan.j.williams@...el.com>
CC:     Navneet Singh <navneet.singh@...el.com>,
        Fan Ni <fan.ni@...sung.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Alison Schofield <alison.schofield@...el.com>,
        "Vishal Verma" <vishal.l.verma@...el.com>,
        <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 08/18] cxl/region: Add Dynamic Capacity CXL region
 support

Dave Jiang wrote:
> 
> 
> On 8/28/23 22:20, Ira Weiny wrote:
> > CXL devices optionally support dynamic capacity.  CXL Regions must be
> > configured correctly to access this capacity.  Similar to ram and pmem
> > partitions, DC Regions represent different partitions of the DPA space.
> > 
> > Interleaving is deferred due to the complexity of managing extents on
> > multiple devices at the same time.  However, there is nothing which
> > directly prevents interleave support at this time.  The check allows
> > for early rejection.
> > 
> > To maintain backwards compatibility with older software, CXL regions
> > need a default DAX device to hold the reference for the region until it
> > is deleted.
> > 
> > Add create_dc_region sysfs entry to create DC regions.  Share the logic
> > of devm_cxl_add_dax_region() and region_is_system_ram().  Special case
> > DC capable CXL regions to create a 0 sized seed DAX device until others
> > can be created on dynamic space later.
> > 
> > Flag dax_regions to indicate 0 capacity available until dax_region
> > extents are supported by the region.
> > 
> > Co-developed-by: Navneet Singh <navneet.singh@...el.com>
> > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> 
> You probably should update kernel version to v6.7. Otherwise

Done.

> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
>