linux-kernel - [PATCH 30/74] x86, lto: Fix AMD K6 indirect call check

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Date:	Sat, 18 Aug 2012 19:56:26 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, mmarek@...e.cz, linux-kbuild@...r.kernel.org,
	JBeulich@...e.com, akpm@...ux-foundation.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 30/74] x86, lto: Fix AMD K6 indirect call check

From: Andi Kleen <ak@...ux.intel.com>

The AMD K6 errata check relies on timing a indirect call.
But the way it was written it could be optimized to a direct call.
Force gcc to actually do a indirect call and not just
constant resolve the target address.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/kernel/cpu/amd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 2c02d92..cb72014 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -116,7 +116,7 @@ static void __cpuinit init_amd_k6(struct cpuinfo_x86 *c)
 		 */
 
 		n = K6_BUG_LOOP;
-		f_vide = vide;
+		asm("" : "=r" (f_vide) : "0" (vide));
 		rdtscl(d);
 		while (n--)
 			f_vide();
-- 
1.7.7.6

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