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Subject[tip:x86/mm] x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52
Commit-ID:  b83ce5ee91471d19c403ff91227204fb37c95fb2
Gitweb: https://git.kernel.org/tip/b83ce5ee91471d19c403ff91227204fb37c95fb2
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate: Wed, 14 Feb 2018 14:16:48 +0300
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 14 Feb 2018 13:11:13 +0100

x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52

__PHYSICAL_MASK_SHIFT is used to define the mask that helps to extract
physical address from a page table entry.

Although real physical address space available may differ between
machines, it's safe to use 52 as __PHYSICAL_MASK_SHIFT. Unused bits
above log2(MAXPHYADDR) up to bit 51 are reserved and must be 0.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@suse.de>
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/20180214111656.88514-2-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/page_64_types.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index e140731..f68e652 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -52,11 +52,12 @@
#define __START_KERNEL_map _AC(0xffffffff80000000, UL)

/* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
-#ifdef CONFIG_X86_5LEVEL
+
#define __PHYSICAL_MASK_SHIFT 52
+
+#ifdef CONFIG_X86_5LEVEL
#define __VIRTUAL_MASK_SHIFT 56
#else
-#define __PHYSICAL_MASK_SHIFT 46
#define __VIRTUAL_MASK_SHIFT 47
#endif

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