From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9F170139D0A for ; Fri, 23 Jan 2026 08:53:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769158429; cv=none; b=jPPVIaZbnsUW1Xx5eut8cUodo6m17AAyOEJmWp1UXUSrCbYlRDtMJ8pfOH5mPqH20QTSmvID3mVW5ODZieCkmPuIQqLj6/AanBy1WA1IB6qn3DcdWI4qZa2DzVV6Zm6aqhhSlRgIR0gsB+eSjv5cfKfw6Q47eXJN/i9T5Oi1W9k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769158429; c=relaxed/simple; bh=8xDScLcsy5OFgIJg5rseIw23Z3H5/7lWSJmJgApIXko=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=E2N7Sla1ZUvwHmRx5c6DSspo1NDFupoHeT+3GfWqc8WRjlGVyllWToHZVTPtu8pmurvgD2N7C4uGV2LONKBFcBjF+wUgloEapzMzMdFmY0FeZbkDLGQ8Gs6Tsn9f1Mu/EM6UkJkg+ncTqeyoRPhYg0GJ4BQJFsON3gGEt84zlrA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EJyy6q4G; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EJyy6q4G" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F1591C4CEF1; Fri, 23 Jan 2026 08:53:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769158429; bh=8xDScLcsy5OFgIJg5rseIw23Z3H5/7lWSJmJgApIXko=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EJyy6q4GWlNjzBtY8qzSezHb7bGJ0MPYYNHtLo9jOXlGE/DhGzq1hfsdoLsqjLcHB KyHB/f8pdvDLTlYmTUYPNPK3Abt0FTBwhzIVXmzVsQmfZp8XB1Fdam7mJLMGII6GzU vGYWSG3J6wWzp/HHPspEPHFPwJiVIyoFxLIrAQoi8SlYn+5CFFzJUw6NavLlmM8SZc we7Wuh+48gW6nIFohR3yz54yhjHR4iYs2YXbW8XS6JyGqb/xIdxXwTjAIncCpcVpp4 JnJb3EpXp66eRrCBIGWkp71VvVprmAHUEBHJVAXxdycnZQtMG+rVlM2T1F+sYDB5UL o13nTXz1H/wWw== Date: Fri, 23 Jan 2026 10:53:42 +0200 From: Mike Rapoport To: Andrew Morton Cc: Evangelos Petrongonas , Pasha Tatashin , Pratyush Yadav , Alexander Graf , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Subject: Re: [PATCH v2] kho: skip memoryless NUMA nodes when reserving scratch areas Message-ID: References: <20260120175913.34368-1-epetron@amazon.de> <20260122152112.1a8be8e7bdab72631234cd69@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260122152112.1a8be8e7bdab72631234cd69@linux-foundation.org> On Thu, Jan 22, 2026 at 03:21:12PM -0800, Andrew Morton wrote: > On Tue, 20 Jan 2026 17:59:11 +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. > > > > 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.