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 346D437F731 for ; Fri, 16 Jan 2026 11:57:17 +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=1768564638; cv=none; b=YZSQtZG8GpnaNUJwqWYkdmsbnBWVg+vvRoZY05W5f0s1uLRGL04lH5VpfVdbBfjeA6ioMuzEGSkktSG9qodrrJD/CUnfchzqMOLP6R4VRi3g0Dlvc1q5xMl+TDajYsw+75+RewM4WZh0sqCbveFghVAqx8OgAM7A7D8zN4LfJJY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768564638; c=relaxed/simple; bh=6SDIwhdUvWr8ewpLO9jVWgrS1866uQekJSM327jVKA0=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=nTGG8hSLkSr63sHR/O7qlFKJ+dM7bb3zhnAYTHSuMsi1sY46UREoiQQZe8L9ZPkgtdOa4DBiGdY2mRfH2VuY77jd8Pueeb8FV+qGvopdUyLQeELiJ1LCoFutaVOKaAcc5aqnWTChXQKA+4s48ADllcrjM2hnvIMGQM5NAlPbd6w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hOcOOVnb; 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="hOcOOVnb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1146CC19423; Fri, 16 Jan 2026 11:57:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768564637; bh=6SDIwhdUvWr8ewpLO9jVWgrS1866uQekJSM327jVKA0=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=hOcOOVnbFJZHY+6yr3s6ggGs2USLu/6pg8AM9s1qhAq8dxpyxu2RQCfeWUItuRHIs jt7/yWca2D2fWNieB8Kz8ZrRGE81TvhXbv/ebxDCRHIg373WcldjDR0aRTFwWdWNlq m25R3zKYRoJ0peAIUvrkdciinHFKOZZpNMTlZEX7wqoZ5/pvj6WJmzYZ4sfi6OqWDQ qLbm64nXLy2tfNhp0vIsCU/8ohNsEQyRdoTySUPjkHTSjyqZOSQYfpacLSWzSwNuC6 UsyefUb9VlmycNTcU1Wp3Sg5JOw+Yijv7QuVGPmlu010D5zSy/SaA/Z2M0duqyAzBv PBdlJSELC0Frw== From: Pratyush Yadav To: Evangelos Petrongonas Cc: Mike Rapoport , Pasha Tatashin , Pratyush Yadav , "Alexander Graf" , Jason Miu , , , , Subject: Re: [PATCH] kho: skip memoryless NUMA nodes when reserving scratch areas In-Reply-To: <20260116112640.64900-1-epetron@amazon.de> (Evangelos Petrongonas's message of "Fri, 16 Jan 2026 11:26:35 +0000") References: <20260116112640.64900-1-epetron@amazon.de> Date: Fri, 16 Jan 2026 11:57:14 +0000 Message-ID: <2vxzsec57oth.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain 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 > --- > 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