From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <ak@linux.intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Andy Lutomirski <luto@amacapital.net>,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: [PATCHv3 11/13] x86/mm: Allow to boot without la57 if CONFIG_X86_5LEVEL=y
Date: Mon, 7 Aug 2017 17:14:49 +0300 [thread overview]
Message-ID: <20170807141451.80934-12-kirill.shutemov@linux.intel.com> (raw)
In-Reply-To: <20170807141451.80934-1-kirill.shutemov@linux.intel.com>
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 <kirill.shutemov@linux.intel.com>
---
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 2c9c4899d9ff..4a1a52f064dc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1408,8 +1408,8 @@ 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
next prev parent reply other threads:[~2017-08-07 14:17 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 14:14 [PATCHv3 00/13] Boot-time switching between 4- and 5-level paging Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 01/13] mm, sparsemem: Allocate mem_section at runtime for SPARSEMEM_EXTREME Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 02/13] x86/kasan: Use the same shadow offset for 4- and 5-level paging Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 03/13] x86/xen: Provide pre-built page tables only for XEN_PV and XEN_PVH Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 04/13] x86/xen: Drop 5-level paging support code from XEN_PV code Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 05/13] x86/boot/compressed/64: Detect and handle 5-level paging at boot-time Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 06/13] x86/mm: Make virtual memory layout movable for CONFIG_X86_5LEVEL Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 07/13] x86/mm: Make PGDIR_SHIFT and PTRS_PER_P4D variable Kirill A. Shutemov
2017-08-07 15:48 ` Andi Kleen
2017-08-07 14:14 ` [PATCHv3 08/13] x86/mm: Handle boot-time paging mode switching at early boot Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 09/13] x86/mm: Fold p4d page table layer at runtime Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 10/13] x86/mm: Replace compile-time checks for 5-level with runtime-time Kirill A. Shutemov
2017-08-07 14:14 ` Kirill A. Shutemov [this message]
2017-08-07 14:14 ` [PATCHv3 12/13] x86/xen: Allow XEN_PV and XEN_PVH to be enabled with X86_5LEVEL Kirill A. Shutemov
2017-08-07 14:14 ` [PATCHv3 13/13] x86/mm: Offset boot-time paging mode switching cost Kirill A. Shutemov
2017-08-07 15:54 ` Andi Kleen
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