linux-kernel - [tip:x86/urgent] x86, kvm: Remove incorrect redundant assembly constraint

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Message-ID: <tip-cb7cb2864e758a1b040040bc55e404c677c911cb@git.kernel.org>
Date:	Mon, 26 Nov 2012 16:01:38 -0800
From:	"tip-bot for H. Peter Anvin" <hpa@...ux.intel.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	pbonzini@...hat.com, mtosatti@...hat.com, tglx@...utronix.de,
	hpa@...ux.intel.com, melanie.blower@...el.com
Subject: [tip:x86/urgent] x86, kvm:
  Remove incorrect redundant assembly constraint

Commit-ID:  cb7cb2864e758a1b040040bc55e404c677c911cb
Gitweb:     http://git.kernel.org/tip/cb7cb2864e758a1b040040bc55e404c677c911cb
Author:     H. Peter Anvin <hpa@...ux.intel.com>
AuthorDate: Wed, 21 Nov 2012 14:41:21 -0800
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Mon, 26 Nov 2012 15:52:48 -0800

x86, kvm: Remove incorrect redundant assembly constraint

In __emulate_1op_rax_rdx, we use "+a" and "+d" which are input/output
constraints, and *then* use "a" and "d" as input constraints.  This is
incorrect, but happens to work on some versions of gcc.

However, it breaks gcc with -O0 and icc, and may break on future
versions of gcc.

Reported-and-tested-by: Melanie Blower <melanie.blower@...el.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Link: http://lkml.kernel.org/r/B3584E72CFEBED439A3ECA9BCE67A4EF1B17AF90@FMSMSX107.amr.corp.intel.com
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Acked-by: Marcelo Tosatti <mtosatti@...hat.com>
---
 arch/x86/kvm/emulate.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 39171cb..bba39bf 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -426,8 +426,7 @@ static void invalidate_registers(struct x86_emulate_ctxt *ctxt)
 			_ASM_EXTABLE(1b, 3b)				\
 			: "=m" ((ctxt)->eflags), "=&r" (_tmp),		\
 			  "+a" (*rax), "+d" (*rdx), "+qm"(_ex)		\
-			: "i" (EFLAGS_MASK), "m" ((ctxt)->src.val),	\
-			  "a" (*rax), "d" (*rdx));			\
+			: "i" (EFLAGS_MASK), "m" ((ctxt)->src.val));	\
 	} while (0)
 
 /* instruction has only one source operand, destination is implicit (e.g. mul, div, imul, idiv) */
--
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