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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 CE211C46475 for ; Mon, 5 Nov 2018 13:45:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9DFDE2085A for ; Mon, 5 Nov 2018 13:45:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9DFDE2085A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729978AbeKEXEz (ORCPT ); Mon, 5 Nov 2018 18:04:55 -0500 Received: from terminus.zytor.com ([198.137.202.136]:58441 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727390AbeKEXEy (ORCPT ); Mon, 5 Nov 2018 18:04:54 -0500 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id wA5DduEx351202 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 5 Nov 2018 05:39:56 -0800 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id wA5DduMB351199; Mon, 5 Nov 2018 05:39:56 -0800 Date: Mon, 5 Nov 2018 05:39:56 -0800 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Borislav Petkov Message-ID: Cc: linux-kernel@vger.kernel.org, bp@suse.de, tglx@linutronix.de, hpa@zytor.com, x86@kernel.org, rppt@linux.ibm.com, mingo@kernel.org Reply-To: x86@kernel.org, rppt@linux.ibm.com, mingo@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, bp@suse.de In-Reply-To: <20181101155314.30690-1-bp@alien8.de> References: <20181101155314.30690-1-bp@alien8.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/cleanups] x86/gart: Rewrite early_gart_iommu_check() comment Git-Commit-ID: 59d130cc9b92b92feaada94a0802fa747038d17f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 59d130cc9b92b92feaada94a0802fa747038d17f Gitweb: https://git.kernel.org/tip/59d130cc9b92b92feaada94a0802fa747038d17f Author: Borislav Petkov AuthorDate: Thu, 1 Nov 2018 16:24:43 +0100 Committer: Borislav Petkov CommitDate: Mon, 5 Nov 2018 14:35:10 +0100 x86/gart: Rewrite early_gart_iommu_check() comment ... to actually explain what the function is trying to do. Reported-by: Mike Rapoport Signed-off-by: Borislav Petkov Reviewed-by: Thomas Gleixner Cc: Link: http://lkml.kernel.org/r/20181101155314.30690-1-bp@alien8.de --- arch/x86/kernel/aperture_64.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c index 2c4d5ece7456..4fb4b7f53568 100644 --- a/arch/x86/kernel/aperture_64.c +++ b/arch/x86/kernel/aperture_64.c @@ -264,18 +264,23 @@ static int __init parse_gart_mem(char *p) } early_param("gart_fix_e820", parse_gart_mem); +/* + * With kexec/kdump, if the first kernel doesn't shutdown the GART and the + * second kernel allocates a different GART region, there might be two + * overlapping GART regions present: + * + * - the first still used by the GART initialized in the first kernel. + * - (sub-)set of it used as normal RAM by the second kernel. + * + * which leads to memory corruptions and a kernel panic eventually. + * + * This can also happen if the BIOS has forgotten to mark the GART region + * as reserved. + * + * Try to update the e820 map to mark that new region as reserved. + */ void __init early_gart_iommu_check(void) { - /* - * in case it is enabled before, esp for kexec/kdump, - * previous kernel already enable that. memset called - * by allocate_aperture/__alloc_bootmem_nopanic cause restart. - * or second kernel have different position for GART hole. and new - * kernel could use hole as RAM that is still used by GART set by - * first kernel - * or BIOS forget to put that in reserved. - * try to update e820 to make that region as reserved. - */ u32 agp_aper_order = 0; int i, fix, slot, valid_agp = 0; u32 ctl;