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

[Jonathan Cameron]

On Mon, 5 Jan 2026 11:34:55 +0200
Mike Rapoport <rppt@xxxxxxxxxx> wrote:

> 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? #
Also, please +CC linux-cxl@xxxxxxxxxxxxxxx given this is all about how
we handle the CXL fixed memory windows.

>  
> > > > 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@xxxxxxxxxxxxxx>  
>