linux-kernel - [tip:x86/asm] x86/asm: Enable fast 32-bit put_user_64() for copy_to

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Date:	Thu, 16 Apr 2015 09:15:41 -0700
From:	tip-bot for Chris Wilson <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	mingo@...nel.org, chris@...is-wilson.co.uk,
	linux-kernel@...r.kernel.org, bp@...en8.de, hpa@...or.com,
	tglx@...utronix.de, torvalds@...ux-foundation.org
Subject: [tip:x86/asm] x86/asm: Enable fast 32-bit put_user_64()
  for copy_to_user()

Commit-ID:  6a907738ab9840ca3d71c22cd28fba4cbae7f7ce
Gitweb:     http://git.kernel.org/tip/6a907738ab9840ca3d71c22cd28fba4cbae7f7ce
Author:     Chris Wilson <chris@...is-wilson.co.uk>
AuthorDate: Wed, 15 Apr 2015 10:51:26 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 16 Apr 2015 12:08:21 +0200

x86/asm: Enable fast 32-bit put_user_64() for copy_to_user()

For fixed sized copies, copy_to_user() will utilize
__put_user_size() fastpaths. However, it is missing the
translation for 64-bit copies on x86/32.

Testing on a Pinetrail Atom, the 64 bit put_user() fastpath
is substantially faster than the generic copy_to_user()
fallback.

Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Borislav Petkov <bp@...en8.de>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: intel-gfx@...ts.freedesktop.org
Link: http://lkml.kernel.org/r/1429091486-11443-1-git-send-email-chris@chris-wilson.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/include/asm/uaccess_32.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/uaccess_32.h b/arch/x86/include/asm/uaccess_32.h
index 3c03a5d..0ed5504 100644
--- a/arch/x86/include/asm/uaccess_32.h
+++ b/arch/x86/include/asm/uaccess_32.h
@@ -59,6 +59,10 @@ __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 			__put_user_size(*(u32 *)from, (u32 __user *)to,
 					4, ret, 4);
 			return ret;
+		case 8:
+			__put_user_size(*(u64 *)from, (u64 __user *)to,
+					8, ret, 8);
+			return ret;
 		}
 	}
 	return __copy_to_user_ll(to, from, n);
--
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