Messages in this thread | | | Date | Tue, 30 Aug 2011 14:39:55 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH x86 kvm] Fix register corruption in pvclock_scale_delta |
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On 08/30/2011 11:58 AM, Duncan Sands wrote: > Hi Zachary, this patch can cause a compile failure if the compiler > chooses to > use a memory location for mul_frac rather than a register (as allowed > by the > "m" in the constraints): > > pvclock.s:229: Error: no instruction mnemonic suffix given and no > register operands; can't size instruction > > In this example the assembler is: > > #APP > mul -48(%rbp) ; shrd $32, %rdx, %rax > #NO_APP > > A simple solution is to use mulq, as in the following patch: > > Signed-off-by: Duncan Sands <baldrick@free.fr> > > --- a/arch/x86/include/asm/pvclock.h > +++ b/arch/x86/include/asm/pvclock.h > @@ -44,7 +44,7 @@ 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 %[mul_frac] ; shrd $32, %[hi], %[lo]" > + "mulq %[mul_frac] ; shrd $32, %[hi], %[lo]" > : [lo]"=a"(product), > [hi]"=d"(tmp) > : "0"(delta),
Thanks, applied.
-- error compiling committee.c: too many arguments to function
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