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[PATCHv5 1/9] x86/asm: Fix comment in return_from_SYSCALL_64

Started by"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
First post2017-04-20 18:30 +0200
Last post2017-04-20 18:30 +0200
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  [PATCHv5 1/9] x86/asm: Fix comment in return_from_SYSCALL_64 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2017-04-20 18:30 +0200

#1627650 — [PATCHv5 1/9] x86/asm: Fix comment in return_from_SYSCALL_64

From"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Date2017-04-20 18:30 +0200
Subject[PATCHv5 1/9] x86/asm: Fix comment in return_from_SYSCALL_64
Message-ID<tyn7X-2LD-11@gated-at.bofh.it>
On x86-64 __VIRTUAL_MASK_SHIFT depends on paging mode now.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 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 607d72c4a485..edec30584eb8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -266,7 +266,8 @@ 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
-- 
2.11.0

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