linux-kernel - Re: [PATCH] mm: numa_memblks: Identify the accurate NUMA ID of CFMW

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Message-ID: <aVuFv7P6og6pY2lj@kernel.org>
Date: Mon, 5 Jan 2026 11:34:55 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Cui Chao <cuichao1753@...tium.com.cn>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Joanthan Cameron <Jonathan.Cameron@...wei.com>,
	wangyinfeng@...tium.com.cn, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: numa_memblks: Identify the accurate NUMA ID of CFMW

On Mon, Jan 05, 2026 at 10:38:30AM +0800, Cui Chao wrote:
> Hi,
> 
> Thank you for your review.
> 
> On 12/30/2025 11:18 PM, Mike Rapoport wrote:
> > Hi,
> > 
> > On Tue, Dec 30, 2025 at 05:27:50PM +0800, Cui Chao wrote:
> > > In some physical memory layout designs, the address space of CFMW
> > > resides between multiple segments of system memory belonging to
> > > the same NUMA node. In numa_cleanup_meminfo, these multiple segments
> > > of system memory are merged into a larger numa_memblk. When
> > > identifying which NUMA node the CFMW belongs to, it may be incorrectly
> > > assigned to the NUMA node of the merged system memory. To address this
> > Can you please provide an example of such memory layout?
> 
> Example memory layout:
> 
> Physical address space:
>     0x00000000 - 0x1FFFFFFF  System RAM (node0)
>     0x20000000 - 0x2FFFFFFF  CXL CFMW (node2)
>     0x40000000 - 0x5FFFFFFF  System RAM (node0)
>     0x60000000 - 0x7FFFFFFF  System RAM (node1)
> 
> After numa_cleanup_meminfo, the two node0 segments are merged into one:
>     0x00000000 - 0x5FFFFFFF  System RAM (node0)  // CFMW is inside this
> range
>     0x60000000 - 0x7FFFFFFF  System RAM (node1)
> 
> So the CFMW (0x20000000-0x2FFFFFFF) will be incorrectly assigned to node0.

Can you please add this example to the changelog? 
 
> > > scenario, accurately identifying the correct NUMA node can be achieved
> > > by checking whether the region belongs to both numa_meminfo and
> > > numa_reserved_meminfo.
> > > 
> > > Signed-off-by: Cui Chao <cuichao1753@...tium.com.cn>

-- 
Sincerely yours,
Mike.