Patch "powerpc/papr_scm: Update the NUMA distance table for the target node" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    powerpc/papr_scm: Update the NUMA distance table for the target node

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-papr_scm-update-the-numa-distance-table-for-.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 6f10cc2df7a3f21bcf639e9b787b21fa262f7d4c
Author: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Date:   Tue Apr 4 09:44:33 2023 +0530

    powerpc/papr_scm: Update the NUMA distance table for the target node
    
    [ Upstream commit b277fc793daf258877b4c0744b52f69d6e6ba22e ]
    
    Platform device helper routines won't update the NUMA distance table
    while creating a platform device, even if the device is present on a
    NUMA node that doesn't have memory or CPU. This is especially true for
    pmem devices. If the target node of the pmem device is not online, we
    find the nearest online node to the device and associate the pmem device
    with that online node. To find the nearest online node, we should have
    the numa distance table updated correctly. Update the distance
    information during the device probe.
    
    For a papr scm device on NUMA node 3 distance_lookup_table value for
    distance_ref_points_depth = 2 before and after fix is below:
    
    Before fix:
      node 3 distance depth 0  - 0
      node 3 distance depth 1  - 0
      node 4 distance depth 0  - 4
      node 4 distance depth 1  - 2
      node 5 distance depth 0  - 5
      node 5 distance depth 1  - 1
    
    After fix
      node 3 distance depth 0  - 3
      node 3 distance depth 1  - 1
      node 4 distance depth 0  - 4
      node 4 distance depth 1  - 2
      node 5 distance depth 0  - 5
      node 5 distance depth 1  - 1
    
    Without the fix, the nearest numa node to the pmem device (NUMA node 3)
    will be picked as 4. After the fix, we get the correct numa node which
    is 5.
    
    Fixes: da1115fdbd6e ("powerpc/nvdimm: Pick nearby online node if the device node is not online")
    Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
    Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
    Link: https://msgid.link/20230404041433.1781804-1-aneesh.kumar@xxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5fb829256b59d..9c038c8cebebc 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -367,6 +367,7 @@ void update_numa_distance(struct device_node *node)
 	WARN(numa_distance_table[nid][nid] == -1,
 	     "NUMA distance details for node %d not provided\n", nid);
 }
+EXPORT_SYMBOL_GPL(update_numa_distance);
 
 /*
  * ibm,numa-lookup-index-table= {N, domainid1, domainid2, ..... domainidN}
diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index f48e87ac89c9b..3cfcc748052e9 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -1159,6 +1159,13 @@ static int papr_scm_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	/*
+	 * open firmware platform device create won't update the NUMA 
+	 * distance table. For PAPR SCM devices we use numa_map_to_online_node()
+	 * to find the nearest online NUMA node and that requires correct
+	 * distance table information.
+	 */
+	update_numa_distance(dn);
 
 	p = kzalloc(sizeof(*p), GFP_KERNEL);
 	if (!p)