From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 3D4F16B04D5 for ; Wed, 23 Aug 2017 08:04:03 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id o82so12510599pfj.11 for ; Wed, 23 Aug 2017 05:04:03 -0700 (PDT) Received: from mga14.intel.com (mga14.intel.com. [192.55.52.115]) by mx.google.com with ESMTPS id u91si986989plb.1010.2017.08.23.05.03.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 23 Aug 2017 05:03:55 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv6 16/19] x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y Date: Wed, 23 Aug 2017 15:03:29 +0300 Message-Id: <20170823120332.2288-17-kirill.shutemov@linux.intel.com> In-Reply-To: <20170823120332.2288-1-kirill.shutemov@linux.intel.com> References: <20170823120332.2288-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar , Linus Torvalds , x86@kernel.org, Thomas Gleixner , "H. Peter Anvin" Cc: Andrew Morton , Andy Lutomirski , Borislav Petkov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" All pieces of the puzzle are in place and we can now allow to boot with CONFIG_X86_5LEVEL=y on a machine without la57 support. Kernel will detect that la57 is missing and fold p4d at runtime. Update documentation and Kconfig option description to reflect the change. Signed-off-by: Kirill A. Shutemov --- Documentation/x86/x86_64/5level-paging.txt | 9 +++------ arch/x86/Kconfig | 4 ++-- arch/x86/include/asm/required-features.h | 8 +------- 3 files changed, 6 insertions(+), 15 deletions(-) diff --git a/Documentation/x86/x86_64/5level-paging.txt b/Documentation/x86/x86_64/5level-paging.txt index 087251a0d99c..2432a5ef86d9 100644 --- a/Documentation/x86/x86_64/5level-paging.txt +++ b/Documentation/x86/x86_64/5level-paging.txt @@ -20,12 +20,9 @@ Documentation/x86/x86_64/mm.txt CONFIG_X86_5LEVEL=y enables the feature. -So far, a kernel compiled with the option enabled will be able to boot -only on machines that supports the feature -- see for 'la57' flag in -/proc/cpuinfo. - -The plan is to implement boot-time switching between 4- and 5-level paging -in the future. +Kernel with CONFIG_X86_5LEVEL=y still able to boot on 4-level hardware. +In this case additional page table level -- p4d -- will be folded at +runtime. == User-space and large virtual address space == diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1e48d2fd8db9..c88db538f3b3 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1411,8 +1411,8 @@ config X86_5LEVEL It will be supported by future Intel CPUs. - Note: a kernel with this option enabled can only be booted - on machines that support the feature. + A kernel with the option enabled can be booted on machines that + support 4- or 5-level paging. See Documentation/x86/x86_64/5level-paging.txt for more information. diff --git a/arch/x86/include/asm/required-features.h b/arch/x86/include/asm/required-features.h index d91ba04dd007..fac9a5c0abe9 100644 --- a/arch/x86/include/asm/required-features.h +++ b/arch/x86/include/asm/required-features.h @@ -53,12 +53,6 @@ # define NEED_MOVBE 0 #endif -#ifdef CONFIG_X86_5LEVEL -# define NEED_LA57 (1<<(X86_FEATURE_LA57 & 31)) -#else -# define NEED_LA57 0 -#endif - #ifdef CONFIG_X86_64 #ifdef CONFIG_PARAVIRT /* Paravirtualized systems may not have PSE or PGE available */ @@ -104,7 +98,7 @@ #define REQUIRED_MASK13 0 #define REQUIRED_MASK14 0 #define REQUIRED_MASK15 0 -#define REQUIRED_MASK16 (NEED_LA57) +#define REQUIRED_MASK16 0 #define REQUIRED_MASK17 0 #define REQUIRED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 18) -- 2.14.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org