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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2018-02-14 19:25:42 +0100
committerIngo Molnar <mingo@kernel.org>2018-02-16 10:48:49 +0100
commit6657fca06e3ffab8d0b3f9d8b397f5ee498952d7 (patch)
tree974d247b3c7459a2d595cc837d69ab84f57913a5 /Documentation/x86
parentx86/mm: Replace compile-time checks for 5-level paging with runtime-time checks (diff)
downloadlinux-6657fca06e3ffab8d0b3f9d8b397f5ee498952d7.tar.xz
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x86/mm: Allow to boot without LA57 if CONFIG_X86_5LEVEL=y
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 the documentation and the Kconfig option description to reflect the change. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Arjan van de Ven <arjan@linux.intel.com> Cc: Borislav Petkov <bp@suse.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180214182542.69302-10-kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/x86')
-rw-r--r--Documentation/x86/x86_64/5level-paging.txt9
1 files changed, 3 insertions, 6 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 ==