[PATCH v2] kho: skip memoryless NUMA nodes when reserving scratch areas

[Mike Rapoport]

On Thu, Jan 22, 2026 at 03:21:12PM -0800, Andrew Morton wrote:
> On Tue, 20 Jan 2026 17:59:11 +0000 Evangelos Petrongonas <epetron at amazon.de> wrote:
> 
> > kho_reserve_scratch() iterates over all online NUMA nodes to allocate
> > per-node scratch memory. On systems with memoryless NUMA nodes (nodes
> > that have CPUs but no memory), memblock_alloc_range_nid() fails because
> > there is no memory available on that node. This causes KHO initialization
> > to fail and kho_enable to be set to false.
> > 
> > Some ARM64 systems have NUMA topologies where certain nodes contain only
> > CPUs without any associated memory. These configurations are valid and
> > should not prevent KHO from functioning.
> > 
> > Fix this by only counting nodes that have memory (N_MEMORY state) and
> > skip memoryless nodes in the per-node scratch allocation loop.
> > 
> 
> So kho is unusable on such machines.
> 
> Should we backport this?  I'm thinking
> 
> Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers").

It's only for v6.18, but sure, why not. 

-- 
Sincerely yours,
Mike.