From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76A59C34022 for ; Mon, 17 Feb 2020 20:48:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4BE1C20801 for ; Mon, 17 Feb 2020 20:48:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="p79DEuOY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729450AbgBQUsE (ORCPT ); Mon, 17 Feb 2020 15:48:04 -0500 Received: from mail.skyhub.de ([5.9.137.197]:53420 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727300AbgBQUsD (ORCPT ); Mon, 17 Feb 2020 15:48:03 -0500 Received: from zn.tnic (p200300EC2F060D00F45FBD97DBAEED4C.dip0.t-ipconnect.de [IPv6:2003:ec:2f06:d00:f45f:bd97:dbae:ed4c]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 0F7821EC0CEA; Mon, 17 Feb 2020 21:48:01 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1581972481; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pXUQLBnvAvbm1QU0WL1QhfsZjIvoahth1MX0a41TYHU=; b=p79DEuOYwU2cg7nsTkWIjVzUeYMUfOM2oJq7zUC9iIhDrlrs2VJLaEpxGkKlibROq7Q6Vr rDOiKgrWgXC6Db3j50vCdvkQRKYDmqaX4X0SGFe7iqcIiONCJ/ZcrdfOOK0iZXvRL3XxD0 o7TkM9NZsmS2iVIQrG7jthIqMRtNa4o= Date: Mon, 17 Feb 2020 21:47:56 +0100 From: Borislav Petkov To: Tony Luck Cc: x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/mce: /dev/mcelog: Dynamically allocate space for machine check records Message-ID: <20200217204756.GE14426@zn.tnic> References: <20200208000551.11364-1-tony.luck@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200208000551.11364-1-tony.luck@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 07, 2020 at 04:05:51PM -0800, Tony Luck wrote: > We have had a hard coded limit of 32 machine check records since the > dawn of time. But as numbers of cores increase, it is possible for > more than 32 errors to be reported before a user process reads from > /dev/mcelog. In this case the additional errors are lost. > > Keep 32 as the minimum. But tune the maximum value up based on the > number of processors. > > Signed-off-by: Tony Luck > --- > arch/x86/include/asm/mce.h | 6 ++-- > arch/x86/kernel/cpu/mce/dev-mcelog.c | 46 ++++++++++++++++------------ > 2 files changed, 29 insertions(+), 23 deletions(-) ... > @@ -214,21 +210,21 @@ static ssize_t mce_chrdev_read(struct file *filp, char __user *ubuf, > > /* Only supports full reads right now */ > err = -EINVAL; > - if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce)) > + if (*off != 0 || usize < mcelog->len*sizeof(struct mce)) Add spaces around that * > goto out; > > - next = mcelog.next; > + next = mcelog->next; > err = 0; > > for (i = 0; i < next; i++) { > - struct mce *m = &mcelog.entry[i]; > + struct mce *m = &mcelog->entry[i]; > > err |= copy_to_user(buf, m, sizeof(*m)); > buf += sizeof(*m); > } > > - memset(mcelog.entry, 0, next * sizeof(struct mce)); > - mcelog.next = 0; > + memset(mcelog->entry, 0, next * sizeof(struct mce)); > + mcelog->next = 0; > > if (err) > err = -EFAULT; ... > @@ -340,6 +336,15 @@ static struct miscdevice mce_chrdev_device = { > static __init int dev_mcelog_init_device(void) > { > int err; > + int mce_log_len; Please sort function local variables declaration in a reverse christmas tree order: longest_variable_name; shorter_var_name; even_shorter; i; > + > + mce_log_len = max(MCE_LOG_MIN_LEN, num_online_cpus()); arch/x86/kernel/cpu/mce/dev-mcelog.c: In function ‘dev_mcelog_init_device’: ./include/linux/kernel.h:835:29: warning: comparison of distinct pointer types lacks a cast 835 | (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) | ^~ ./include/linux/kernel.h:849:4: note: in expansion of macro ‘__typecheck’ 849 | (__typecheck(x, y) && __no_side_effects(x, y)) | ^~~~~~~~~~~ ./include/linux/kernel.h:859:24: note: in expansion of macro ‘__safe_cmp’ 859 | __builtin_choose_expr(__safe_cmp(x, y), \ | ^~~~~~~~~~ ./include/linux/kernel.h:875:19: note: in expansion of macro ‘__careful_cmp’ 875 | #define max(x, y) __careful_cmp(x, y, >) | ^~~~~~~~~~~~~ arch/x86/kernel/cpu/mce/dev-mcelog.c:341:16: note: in expansion of macro ‘max’ 341 | mce_log_len = max(MCE_LOG_MIN_LEN, num_online_cpus()); | ^~~ That MCE_LOG_MIN_LEN wants to be 32U. > + mcelog = kzalloc(sizeof(*mcelog) + mce_log_len * sizeof(struct mce), GFP_KERNEL); > + if (!mcelog) > + return -ENOMEM; <---- newline here. > + strncpy(mcelog->signature, MCE_LOG_SIGNATURE, sizeof(mcelog->signature)); > + mcelog->len = mce_log_len; > + mcelog->recordlen = sizeof(struct mce); > > /* register character device /dev/mcelog */ > err = misc_register(&mce_chrdev_device); Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette