From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E2418237180; Tue, 21 Jul 2026 20:31:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784665905; cv=none; b=hX+/Fpq3M58PzhrzExNSzv69yN4wC/PQ+YbX/KW3+XVkCeiNpCZx4l78NIOm5FD78aaHB23ZG4G82oHuRiVVsq+dcdawON12/p0bchfU8s87WW4Km96OVMkTiT41kIJOYY+IbFOmcwveHljIWAS8xASs33NDg99kwXSxPU34bME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784665905; c=relaxed/simple; bh=oTMRXdsDXP7F5yho7IwE2cSulM3N0w7bTRya46eC2l4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u7RFkz3EQ+SVNxwbGWMUh1cSn3lYL35hJcw9TiZXbeCFXmuQsB8fGrlLy82hc3wfEOaigezF04ejN5IKlpAIq/hW1MdTH8wD30f1QpWUjDlnWogYIuSgh2RGOAInesYRuut65Aw1vlO77Q0CRcisIxmPaTClcIAEGhY4Qo69UnA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=DnOVtSyK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="DnOVtSyK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49AD51F000E9; Tue, 21 Jul 2026 20:31:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784665903; bh=T/3s0w314ciEOU/Uc6jBpcEuPSl0UMcUWbNjWRXHKZQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=DnOVtSyKG8mjjowiVF+vmJE0vdZKMKP3E32iWB/DFl48mbiReYdL1cRtVa4AoTzQZ LYz4UgP7CoeRTpOD/1cvfcpmga3pfY80H8GtS9hdtUQQmSlDlnESyuP+64g68GGWXb LAF0kdCC39mZUqbqJDdzCkxw/dgj1TYN+mbBIVfY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sang-Heon Jeon , Donghyeon Lee , Munhui Chae , "Mike Rapoport (Microsoft)" , Sasha Levin Subject: [PATCH 6.6 0480/1266] mm/fake-numa: fix under-allocation detection in uniform split Date: Tue, 21 Jul 2026 17:15:17 +0200 Message-ID: <20260721152452.578125447@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152441.786066624@linuxfoundation.org> References: <20260721152441.786066624@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Sang-Heon Jeon [ Upstream commit 3a3fc1dfd6a958615ebaab8fb251e89fc2b3f2f2 ] When splitting NUMA node uniformly, split_nodes_size_interleave_uniform() returns the next absolute node ID, not the number of nodes created. The existing under-allocation detection logic compares next absolute node ID (ret) and request count (n), which only works when nid starts at 0. For example, on a system with 2 physical NUMA nodes (node 0: 2GB, node 1: 128MB) and numa=fake=8U, 8 fake nodes are successfully created from node 0 and split_nodes_size_interleave_uniform() returns 8. For node 1, fake node nid starts at 8, but only 4 fake nodes are created due to current FAKE_NODE_MIN_SIZE being 32MB, and split_nodes_size_interleave_uniform() returns 12. By existing under-allocation detection logic, "ret < n" (12 < 8) is false, so the under-allocation will not be detected. Fix under-allocation detection logic to compare the number of actually created nodes (ret - nid) against the request count (n). Also skip under-allocation detection logic for memoryless physical nodes where no fake nodes are created. Also, fix the outdated comment describing split_nodes_size_interleave_uniform() to match the actual return value. Signed-off-by: Sang-Heon Jeon Reported-by: Donghyeon Lee Reported-by: Munhui Chae Fixes: cc9aec03e58f ("x86/numa_emulation: Introduce uniform split capability") # 4.19 Link: https://patch.msgid.link/20260417135805.1758378-1-ekffu200098@gmail.com Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Sasha Levin --- arch/x86/mm/numa_emulation.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/numa_emulation.c b/arch/x86/mm/numa_emulation.c index 9a9305367fdd16..b8ae605537145e 100644 --- a/arch/x86/mm/numa_emulation.c +++ b/arch/x86/mm/numa_emulation.c @@ -211,7 +211,7 @@ static u64 uniform_size(u64 max_addr, u64 base, u64 hole, int nr_nodes) * Sets up fake nodes of `size' interleaved over physical nodes ranging from * `addr' to `max_addr'. * - * Returns zero on success or negative on error. + * Returns node ID of the next node on success or negative error code. */ static int __init split_nodes_size_interleave_uniform(struct numa_meminfo *ei, struct numa_meminfo *pi, @@ -395,7 +395,7 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt) if (strchr(emu_cmdline, 'U')) { nodemask_t physnode_mask = numa_nodes_parsed; unsigned long n; - int nid = 0; + int nid = 0, nr_created; n = simple_strtoul(emu_cmdline, &emu_cmdline, 0); ret = -1; @@ -413,9 +413,18 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt) n, &pi.blk[0], nid); if (ret < 0) break; - if (ret < n) { + + /* + * If no memory was found for this physical node, + * skip the under-allocation check. + */ + if (ret == nid) + continue; + + nr_created = ret - nid; + if (nr_created < n) { pr_info("%s: phys: %d only got %d of %ld nodes, failing\n", - __func__, i, ret, n); + __func__, i, nr_created, n); ret = -1; break; } -- 2.53.0