linux-kernel - [106/107] KVM: Fix register corruption in pvclock_scale

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Date:	Thu, 07 Jul 2011 17:17:18 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org, greg@...ah.com
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	avi@...hat.com, mtosatti@...hat.com,
	Zachary Amsden <zamsden@...hat.com>
Subject: [106/107] KVM: Fix register corruption in pvclock_scale_delta

2.6.39-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Zachary Amsden <zamsden@...hat.com>

(cherry picked from commit de2d1a524e94a79078d9fe22c57c0c6009237547)

The 128-bit multiply in pvclock.h was missing an output constraint for
EDX which caused a register corruption to appear.  Thanks to Ulrich for
diagnosing the EDX corruption and Avi for providing this fix.

Signed-off-by: Zachary Amsden <zamsden@...hat.com>
Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 arch/x86/include/asm/pvclock.h |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -22,6 +22,8 @@ static inline u64 pvclock_scale_delta(u6
 	u64 product;
 #ifdef __i386__
 	u32 tmp1, tmp2;
+#else
+	ulong tmp;
 #endif
 
 	if (shift < 0)
@@ -42,8 +44,11 @@ static inline u64 pvclock_scale_delta(u6
 		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
 #elif defined(__x86_64__)
 	__asm__ (
-		"mul %%rdx ; shrd $32,%%rdx,%%rax"
-		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
+		"mul %[mul_frac] ; shrd $32, %[hi], %[lo]"
+		: [lo]"=a"(product),
+		  [hi]"=d"(tmp)
+		: "0"(delta),
+		  [mul_frac]"rm"((u64)mul_frac));
 #else
 #error implement me!
 #endif


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