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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 5C62BC282C2 for ; Wed, 6 Feb 2019 18:13:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1B75E20821 for ; Wed, 6 Feb 2019 18:13:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729107AbfBFSNT (ORCPT ); Wed, 6 Feb 2019 13:13:19 -0500 Received: from terminus.zytor.com ([198.137.202.136]:43733 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726270AbfBFSNT (ORCPT ); Wed, 6 Feb 2019 13:13:19 -0500 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id x16ID7Ib1391439 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Wed, 6 Feb 2019 10:13:07 -0800 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id x16ID7L51391435; Wed, 6 Feb 2019 10:13:07 -0800 Date: Wed, 6 Feb 2019 10:13:07 -0800 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: "tip-bot for Kirill A. Shutemov" Message-ID: Cc: wei@redhat.com, bp@suse.de, mingo@kernel.org, kirill.shutemov@linux.intel.com, mingo@redhat.com, hpa@zytor.com, kyle.d.pelton@intel.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, x86@kernel.org Reply-To: x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, kyle.d.pelton@intel.com, hpa@zytor.com, mingo@kernel.org, mingo@redhat.com, kirill.shutemov@linux.intel.com, bp@suse.de, wei@redhat.com In-Reply-To: <20190206154756.matwldebbxkmlnae@black.fi.intel.com> References: <20190206154756.matwldebbxkmlnae@black.fi.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/cleanups] x86/boot/compressed/64: Explain paging_prepare()'s return value Git-Commit-ID: 82434d23f36de42f70925f70d645ed3b1394361b 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: 82434d23f36de42f70925f70d645ed3b1394361b Gitweb: https://git.kernel.org/tip/82434d23f36de42f70925f70d645ed3b1394361b Author: Kirill A. Shutemov AuthorDate: Wed, 6 Feb 2019 18:29:08 +0300 Committer: Borislav Petkov CommitDate: Wed, 6 Feb 2019 19:08:34 +0100 x86/boot/compressed/64: Explain paging_prepare()'s return value paging_prepare() returns a two-quadword structure which lands into RDX:RAX: - Address of the trampoline is returned in RAX. - Non zero RDX means trampoline needs to enable 5-level paging. Document that explicitly. Signed-off-by: Kirill A. Shutemov Signed-off-by: Borislav Petkov Cc: dave.hansen@linux.intel.com Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Kyle D Pelton Cc: Thomas Gleixner Cc: Wei Huang Cc: x86-ml Link: https://lkml.kernel.org/r/20190206154756.matwldebbxkmlnae@black.fi.intel.com --- arch/x86/boot/compressed/head_64.S | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index b27b338d2f6d..73b9d7e91a9c 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -358,8 +358,11 @@ ENTRY(startup_64) * paging_prepare() sets up the trampoline and checks if we need to * enable 5-level paging. * - * Address of the trampoline is returned in RAX. - * Non zero RDX on return means we need to enable 5-level paging. + * paging_prepare() returns a two-quadword structure which lands + * into RDX:RAX: + * - Address of the trampoline is returned in RAX. + * - Non zero RDX means trampoline needs to enable 5-level + * paging. * * RSI holds real mode data and needs to be preserved across * this function call. @@ -565,7 +568,7 @@ adjust_got: * * RDI contains the return address (might be above 4G). * ECX contains the base address of the trampoline memory. - * Non zero RDX on return means we need to enable 5-level paging. + * Non zero RDX means trampoline needs to enable 5-level paging. */ ENTRY(trampoline_32bit_src) /* Set up data and stack segments */