lkml.org 
[lkml]   [2011]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH x86 kvm] Fix register corruption in pvclock_scale_delta
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 (which now
I am sending back to you Avi..)

Zach
From Avi and Ulrich, fix constraints for 128-bit multiply

Signed-off-by: Zachary Amsden <zamsden@redhat.com>

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 31d84ac..a518c0a 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -22,6 +22,8 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
u64 product;
#ifdef __i386__
u32 tmp1, tmp2;
+#else
+ ulong tmp;
#endif

if (shift < 0)
@@ -42,8 +44,11 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
: "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
\
 
 \ /
  Last update: 2011-06-16 05:53    [W:0.040 / U:1.112 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site