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Date: Sat, 7 Sep 2024 20:24:58 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Huang Ying <ying.huang@intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 linux-cxl@vger.kernel.org, Dan Williams <dan.j.williams@intel.com>, David
 Hildenbrand <david@redhat.com>, Davidlohr Bueso <dave@stgolabs.net>,
 Jonathan Cameron <jonathan.cameron@huawei.com>, Dave Jiang
 <dave.jiang@intel.com>, Alison Schofield <alison.schofield@intel.com>,
 Vishal Verma <vishal.l.verma@intel.com>, Ira Weiny <ira.weiny@intel.com>,
 Alistair Popple <apopple@nvidia.com>, Andy Shevchenko
 <andriy.shevchenko@linux.intel.com>, Bjorn Helgaas <bhelgaas@google.com>,
 Baoquan He <bhe@redhat.com>
Subject: Re: [PATCH -v3 1/3] resource: Fix region_intersects() vs
 add_memory_driver_managed()
Message-Id: <20240907202458.dfe90bfee071021706af91eb@linux-foundation.org>
In-Reply-To: <20240906030713.204292-2-ying.huang@intel.com>
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	<20240906030713.204292-2-ying.huang@intel.com>
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On Fri,  6 Sep 2024 11:07:11 +0800 Huang Ying <ying.huang@intel.com> wrote:

> On a system with CXL memory, the resource tree (/proc/iomem) related
> to CXL memory may look like something as follows.
> 
> 490000000-50fffffff : CXL Window 0
>   490000000-50fffffff : region0
>     490000000-50fffffff : dax0.0
>       490000000-50fffffff : System RAM (kmem)
> 
> Because drivers/dax/kmem.c calls add_memory_driver_managed() during
> onlining CXL memory, which makes "System RAM (kmem)" a descendant of
> "CXL Window X".  This confuses region_intersects(), which expects all
> "System RAM" resources to be at the top level of iomem_resource.  This
> can lead to bugs.
> 
> ...
> 
> Fixes: c221c0b0308f ("device-dax: "Hotplug" persistent memory for use like normal RAM")

Do you believe this should be fixed in earlier (-stable) kernels?