From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id D8A116B0387 for ; Tue, 8 Aug 2017 08:54:34 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id i192so33885146pgc.11 for ; Tue, 08 Aug 2017 05:54:34 -0700 (PDT) Received: from mga05.intel.com (mga05.intel.com. [192.55.52.43]) by mx.google.com with ESMTPS id 77si846787pfn.385.2017.08.08.05.54.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Aug 2017 05:54:33 -0700 (PDT) From: "Kirill A. Shutemov" Subject: [PATCHv4 12/14] x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y Date: Tue, 8 Aug 2017 15:54:13 +0300 Message-Id: <20170808125415.78842-13-kirill.shutemov@linux.intel.com> In-Reply-To: <20170808125415.78842-1-kirill.shutemov@linux.intel.com> References: <20170808125415.78842-1-kirill.shutemov@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds , Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Cc: Andi Kleen , Dave Hansen , Andy Lutomirski , Michal Hocko , 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 ac3358bb7bd2..939698570aa1 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1409,8 +1409,8 @@ 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) -- 2.13.2 -- 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