Commit-ID:  cbe0317bf10acf1f41811108ed0f9a316103c0f3
Gitweb:     http://git.kernel.org/tip/cbe0317bf10acf1f41811108ed0f9a316103c0f3
Author:     Kirill A. Shutemov <kirill.shute...@linux.intel.com>
AuthorDate: Tue, 6 Jun 2017 14:31:21 +0300
Committer:  Ingo Molnar <mi...@kernel.org>
CommitDate: Tue, 13 Jun 2017 08:56:51 +0200

x86/asm: Fix comment in return_from_SYSCALL_64()

On x86-64 __VIRTUAL_MASK_SHIFT depends on paging mode now.

Signed-off-by: Kirill A. Shutemov <kirill.shute...@linux.intel.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Andy Lutomirski <l...@amacapital.net>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Dave Hansen <dave.han...@intel.com>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux-a...@vger.kernel.org
Cc: linux...@kvack.org
Link: 
http://lkml.kernel.org/r/20170606113133.22974-3-kirill.shute...@linux.intel.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 arch/x86/entry/entry_64.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 4a4c083..a9a8027 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -265,7 +265,8 @@ return_from_SYSCALL_64:
         * If width of "canonical tail" ever becomes variable, this will need
         * to be updated to remain correct on both old and new CPUs.
         *
-        * Change top 16 bits to be the sign-extension of 47th bit
+        * Change top bits to match most significant bit (47th or 56th bit
+        * depending on paging mode) in the address.
         */
        shl     $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx
        sar     $(64 - (__VIRTUAL_MASK_SHIFT+1)), %rcx

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