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

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Message-Id: <20260122152112.1a8be8e7bdab72631234cd69@linux-foundation.org>
Date: Thu, 22 Jan 2026 15:21:12 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Evangelos Petrongonas <epetron@...zon.de>
Cc: Mike Rapoport <rppt@...nel.org>, 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, 20 Jan 2026 17:59:11 +0000 Evangelos Petrongonas <epetron@...zon.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").