From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793706599; b=SpTszQU8d95eZhsd17JQFxU+cc86t3IkquW10uomfoEuSy13C9UbzI9B8z8ZaPjPkdK5 GV70cLNdgUWnfCWBymUSRmRw43j7ay3xLKdQ4azBHZb/oKghlmdORghQCt8RRYMfS/zrO 8lLngmNNKW2aX0lHhhEZRl9uMUGjyiLoFRyq+USxWy4BRVNyUJJtUAtqknFM2DgqJjg5B ANr946TOoZlS/OyS1XEDrcB/T94NpKPNN/6FA45gMnT3g0iYnb+8bXZYS0enX5gizYenK 71QVGNY7+nrNp5WXyNfqxlDrTiDg8cK9Jqa+JOTCpCpfNZCUsWN6MU1/c1dmJRJ0NHw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793706599; h=Received:DKIM-Signature:From:Date:Subject:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-Id:References:In-Reply-To:To:Cc: X-Mailer; bh=RWGTnd8ZidzEdipCYzKE95gvRo3h3EOL4P9sMK0ko0A=; b=eTYC+bB6oWXe1Q/e//X20BWlMYCygZ+c/qLeOMcfmSsicpqW+fMWF+e81kH7YZ8sFtrt 5ClpQCLAKm17QvD4bIuRLEpVsgcad25b8RcbPUS0H1mB/ITbvDnmjrvGtrFMO+6kyP5O1 k6bV8pk7GAwxrLNSEJ4ShPaFzGsGAX4X/7WJa+mk3wLnbziI0P92YP9XN0dseDB3NObT1 mfaWQ5rrDWfhnNjK/CZ6uu8T44Y2if1CP+Z4yvsvog9UiBqxLOdp0eIVTul/OwrLa/VJF mnrxipkPgW1mS+r0/KY8vICcWS6LIlqrnTxslfII/VOZfZB1PQ+hpLTfvwFbUCnHFxQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GfdTNGFn; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 37050606D824 for ; Tue, 3 Nov 2026 11:49:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=GfdTNGFn Received: by smtp.kernel.org (Postfix) with ESMTPSA id 34AA61F00A02; Tue, 3 Nov 2026 11:49:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793706598; bh=RWGTnd8ZidzEdipCYzKE95gvRo3h3EOL4P9sMK0ko0A=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=GfdTNGFn0HMpOe8AvhCd2j1aZaNVz68H5nNKxBveUcdY9soH3f+JDh52AHmXHom6W PuimrJhvNrrYP0LNSX+uwodX/q3H5aLF1SQ5SR7HoJBzInc424buwd+htB5fxjsfKP h0m/6Xs1nv1blG5kAfyD20FtoIP5R6I4qJS3f6p8dOcm2Dx06RICbcndZIF7lvkZSn uZhjwPsgeG/2yP29FpLGebEvzUuYgViPZA3POGPmlP7tR8dGtVEMYSLnKC1UzDLap1 6QjqF3kkuGDzQs63Zs4RQ+I1qytybEp/QaYs4mKO5OVEvuLUnIPDVTTj5hJQzpoGCx ef3ZcMvr9pMVg== From: "Mike Rapoport (Microsoft)" Date: Tue, 03 Nov 2026 13:49:49 +0200 Subject: [PATCH 1/2] kho: skip zero-sized lowmem and global bootmem areas X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261103-kho-bootmem-sizing-v1-1-45aa74098f34@kernel.org> References: <20261103-kho-bootmem-sizing-v1-0-45aa74098f34@kernel.org> In-Reply-To: <20261103-kho-bootmem-sizing-v1-0-45aa74098f34@kernel.org> To: Mike Rapoport , Pasha Tatashin , Pratyush Yadav Cc: Alexander Graf , Andrew Morton , Chen Pei , George Guo , Kexin Liu , Sourabh Jain , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org X-Mailer: b4 0.16.1-dev The lowmem and the global bootmem areas can have zero size, for example when none or all of the memory is below ARCH_LOW_ADDRESS_LIMIT, or when either of those areas is explicitly set to zero with kho_bootmem=. For a zero-sized allocation memblock returns an address without reserving anything, and that empty area is recorded in kho_bootmem. If there is no memory below ARCH_LOW_ADDRESS_LIMIT, allocation of the empty lowmem area fails and KHO gets disabled. Extract a helper that checks for zero size and allocates memory from memblock, and use it to skip empty areas the same way as empty per-node areas are skipped. Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers") Reported-by: Chen Pei Closes: https://lore.kernel.org/all/20261026131851.9942-1-cp0613@linux.alibaba.com Signed-off-by: Mike Rapoport (Microsoft) --- kernel/liveupdate/kexec_handover.c | 61 ++++++++++++++++++-------------------- 1 file changed, 29 insertions(+), 32 deletions(-) diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c index 6f1f55fe31819..f268c57413a7e 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -820,6 +820,27 @@ bool kho_bootmem_overlap(phys_addr_t phys, size_t size) return false; } +static int __init kho_reserve_bootmem_area(int *idx, phys_addr_t size, + phys_addr_t end, int nid) +{ + phys_addr_t addr; + int i = *idx; + + if (!size) + return 0; + + addr = memblock_alloc_range_nid(size, BOOTMEM_ALIGNMENT_BYTES, 0, end, + nid, true); + if (!addr) + return -ENOMEM; + + kho_bootmem[i].addr = addr; + kho_bootmem[i].size = size; + *idx = i + 1; + + return 0; +} + /** * kho_reserve_bootmem - Reserve a contiguous chunk of memory for kexec * @@ -832,7 +853,7 @@ bool kho_bootmem_overlap(phys_addr_t phys, size_t size) static void __init kho_reserve_bootmem(void) { int nid, i = 0, max_nr_bootmem; - phys_addr_t addr, size; + phys_addr_t size; if (!kho_enable) return; @@ -852,56 +873,32 @@ static void __init kho_reserve_bootmem(void) * reserve bootmem area in low memory for lowmem allocations in the * next kernel */ - size = bootmem_size_lowmem; - addr = memblock_phys_alloc_range(size, BOOTMEM_ALIGNMENT_BYTES, 0, - ARCH_LOW_ADDRESS_LIMIT); - if (!addr) { + if (kho_reserve_bootmem_area(&i, bootmem_size_lowmem, + ARCH_LOW_ADDRESS_LIMIT, NUMA_NO_NODE)) { pr_err("Failed to reserve lowmem bootmem\n"); goto err_free_bootmem_desc; } - kho_bootmem[i].addr = addr; - kho_bootmem[i].size = size; - i++; - /* reserve large contiguous area for allocations without nid */ - size = bootmem_size_global; - addr = memblock_phys_alloc(size, BOOTMEM_ALIGNMENT_BYTES); - if (!addr) { + if (kho_reserve_bootmem_area(&i, bootmem_size_global, + MEMBLOCK_ALLOC_ACCESSIBLE, NUMA_NO_NODE)) { pr_err("Failed to reserve global bootmem\n"); goto err_free_bootmem_areas; } - kho_bootmem[i].addr = addr; - kho_bootmem[i].size = size; - i++; - /* * Loop over nodes that have both memory and are online. Skip * memoryless nodes, as we can not allocate bootmem areas there. */ for_each_node_state(nid, N_MEMORY) { - size = bootmem_size_node(nid); - if (!size) - continue; - - addr = memblock_alloc_range_nid(size, BOOTMEM_ALIGNMENT_BYTES, - 0, MEMBLOCK_ALLOC_ACCESSIBLE, - nid, true); - if (!addr) { + if (kho_reserve_bootmem_area(&i, bootmem_size_node(nid), + MEMBLOCK_ALLOC_ACCESSIBLE, nid)) { pr_err("Failed to reserve nid %d bootmem\n", nid); goto err_free_bootmem_areas; } - - kho_bootmem[i].addr = addr; - kho_bootmem[i].size = size; - i++; } - /* - * Nodes that needed no bootmem were skipped, so fewer areas than - * initially estimated may have been reserved. - */ + /* Areas with zero size were skipped */ kho_bootmem_cnt = i; return; -- 2.53.0