Hi Evangelos, On Fri, Jan 16 2026, Evangelos Petrongonas 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 introducing kho_mem_nodes_count() which counts only nodes > that have memory (N_MEMORY state), and skip memoryless nodes in the > per-node scratch allocation loop. > > Signed-off-by: Evangelos Petrongonas <[email protected]> > --- > kernel/liveupdate/kexec_handover.c | 23 ++++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/kernel/liveupdate/kexec_handover.c > b/kernel/liveupdate/kexec_handover.c > index 9dc51fab604f..c970ed08b477 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -623,6 +623,23 @@ static phys_addr_t __init scratch_size_node(int nid) > return round_up(size, CMA_MIN_ALIGNMENT_BYTES); > } > > +/* > + * Count online NUMA nodes that have memory. Memoryless nodes cannot have > + * scratch memory and should be excluded. > + */ > +static unsigned int __init kho_mem_nodes_count(void) > +{ > + unsigned int cnt = 0; > + int nid; > + > + for_each_online_node(nid) { > + if (node_state(nid, N_MEMORY)) > + cnt++; > + } > + > + return cnt; > +} > + You don't need this. You can use nodes_weight(nodes_state[N_MEMORY]) directly. Other than this, LGTM. > /** > * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec > * > @@ -643,7 +660,7 @@ static void __init kho_reserve_scratch(void) > scratch_size_update(); > > /* FIXME: deal with node hot-plug/remove */ > - kho_scratch_cnt = num_online_nodes() + 2; > + kho_scratch_cnt = kho_mem_nodes_count() + 2; > size = kho_scratch_cnt * sizeof(*kho_scratch); > kho_scratch = memblock_alloc(size, PAGE_SIZE); > if (!kho_scratch) > @@ -674,6 +691,10 @@ static void __init kho_reserve_scratch(void) > i++; > > for_each_online_node(nid) { > + /* Skip memoryless nodes - we cannot allocate scratch memory > there */ > + if (!node_state(nid, N_MEMORY)) > + continue; > + > size = scratch_size_node(nid); > addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES, > 0, MEMBLOCK_ALLOC_ACCESSIBLE, -- Regards, Pratyush Yadav
