linux-kernel - Re: [PATCH v2] kho: skip memoryless NUMA nodes when reserving scratch areas

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aW_Qtz6X-XErS74D@kernel.org>
Date: Tue, 20 Jan 2026 21:00:07 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Evangelos Petrongonas <epetron@...zon.de>
Cc: Pasha Tatashin <pasha.tatashin@...een.com>,
	Pratyush Yadav <pratyush@...nel.org>,
	Alexander Graf <graf@...zon.com>, Jason Miu <jasonmiu@...gle.com>,
	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	linux-mm@...ck.org, nh-open-source@...zon.com
Subject: Re: [PATCH v2] kho: skip memoryless NUMA nodes when reserving
 scratch areas

On Tue, Jan 20, 2026 at 05:59:11PM +0000, 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 only counting nodes that have memory (N_MEMORY state) and
> skip memoryless nodes in the per-node scratch allocation loop.
> 
> Signed-off-by: Evangelos Petrongonas <epetron@...zon.de>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

> ---
> v2:
> - Removed kho_mem_nodes_count in favour of nodes_weight(nodes_state[N_MEMORY])
> - Use for_each_node_state(nid, N_MEMORY) to loop over nodes that are both
> online and have memory.
> TIL: Nodes in N_MEMORY are a subset of those that are online. Thanks Mike :)
> 
>  kernel/liveupdate/kexec_handover.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 9dc51fab604f..979ebaf015bf 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -643,7 +643,7 @@ 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 = nodes_weight(node_states[N_MEMORY]) + 2;
>  	size = kho_scratch_cnt * sizeof(*kho_scratch);
>  	kho_scratch = memblock_alloc(size, PAGE_SIZE);
>  	if (!kho_scratch)
> @@ -673,7 +673,11 @@ static void __init kho_reserve_scratch(void)
>  	kho_scratch[i].size = size;
>  	i++;
>  
> -	for_each_online_node(nid) {
> +	/*
> +	 * Loop over nodes that have both memory and are online. Skip
> +	 * memoryless nodes, as we can not allocate scratch areas there.
> +	 */
> +	for_each_node_state(nid, N_MEMORY) {
>  		size = scratch_size_node(nid);
>  		addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
>  						0, MEMBLOCK_ALLOC_ACCESSIBLE,
> -- 
> 2.43.0
> 
> 
> 
> 
> Amazon Web Services Development Center Germany GmbH
> Tamara-Danz-Str. 13
> 10243 Berlin
> Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger
> Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
> Sitz: Berlin
> Ust-ID: DE 365 538 597
> 

-- 
Sincerely yours,
Mike.