Re: problem wit svm_get_msr on kvm-kmod-2.6.31.6

[Avi Kivity <avi@redhat.com>]

On 11/16/2009 01:17 PM, Dietmar Maurer wrote:
>      38f0:       0f 85 82 01 00 00       jne    3a78<svm_get_msr+0x2b8>
>      38f6:       48 8b 87 e0 27 00 00    mov    0x27e0(%rdi),%rax
>      38fd:       48 8b 48 50             mov    0x50(%rax),%rcx
>      3901:       0f 31                   rdtsc
>      3903:       48 01 c8                add    %rcx,%rax
>
> # this is svm_get_msr+0x146
>      3906:       48 89 02                mov    %rax,(%rdx)
>    


Looks like a miscompile of native_read_tsc(), it needs to use %edx:%eax, 
not assume the result is in %rax.

Jan, looks like the culprit is

   static inline unsigned long long kvm_native_read_tsc(void)
   {
         unsigned long long val;
         asm volatile("rdtsc" : "=A" (val));
         return val;
   }

"=A" only works correctly on i386, need to use "=a" "=d" for portability.

-- 
error compiling committee.c: too many arguments to function