RE: [PATCH 0/2] x86/numa: Fix NUMA node overlap & init failure

[Dan Williams <dan.j.williams@intel.com>]

alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> A previously posted single patch [1] is obsoleted by this set. The
> feedback from that review is applied and noted in Patch 1.
> 
> While trying to attribute a CXL user report to the bad selection of
> overlapping memblks, as fixed in Patch 1, I found that two issues,
> in sequence, lead to NUMA Node overlap and NUMA init failure.
> 
> An overlapping NUMA node occurs when a non-overlapping memblk is
> selected to fill (Patch 1), and then a bad sort (Patch 2) puts the
> memblk with the greater address ahead of the lesser address memblk
> in the fill list.
> 
> It looked like this:
> 
> Existing memblks:
> 	node 6 [mem 0xb90000000-0xc90000000]
> 	node 7 [mem 0xc90000000-0xd90000000]
> 
> Call to numa_fill_memblks(b90000000,c90000000)
> 
> Error (Patch 1): collects 2 blks  
> 	blk[0] node 6 [0xb90000000-0xc90000000]
> 	blk[1] node 7 [0xc90000000-0xd90000000]
> 
> Error (Patch 2): bad sort of the 2 blks
> 	blk[0] node 7 [0xc90000000-0xd90000000]
> 	blk[1] node 6 [0xb90000000-0xc90000000]
> 
> Seals the deal with a bad fill:
> 	blk[0] node 7 [0xb90000000-0xd90000000]
> 
> Boom: numa_clean_meminfo() discovers the overlap in Nodes 6 & 7
> and NUMA init fails.
> 
> Since the scenario above is not solely attributed to either patch,
> the story is explicity shared here.
> 
> [1] https://lore.kernel.org/linux-cxl/20240102213206.1493733-1-alison.schofield@intel.com/
> 
> Alison Schofield (2):
>   x86/numa: Fix the address overlap check in numa_fill_memblks()
>   x86/numa: Fix the sort compare func used in numa_fill_memblks()
> 
>  arch/x86/mm/numa.c       | 21 ++++++++-------------
>  include/linux/memblock.h |  2 ++
>  mm/memblock.c            |  5 +++--
>  3 files changed, 13 insertions(+), 15 deletions(-)

For both fixes:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

...if they get picked up into the x86 tree.

Otherwise I'll circle back and take them through cxl.git with an x86 ack
since this is all cxl-related fixups to numa_fill_memblks().