Re: Current KVM head crashes on startup

[Avi Kivity <avi@redhat.com>]

Amit Shah wrote:
>> I don't recall, it probably depends on whether frame pointers are used  
>> or not as well.
>>     
>
> As far as I know, kvm-userspace build arguments have remained the same
> for quite some time. Also, we still pass the -g flag for userspace
> compilations.
>
>   

Some distros change CFLAGS.

>>>  -- maintaining
>>> specific code can introduce such regressions.
>>>   
>>>       
>> That's a problem with assembly.  x86 and x86_64 are different  
>> instruction sets.
>>     
>
> But the code in question isn't different on the two architectures. Just
> a cpuid call that hasn't changed.
>
>   

The amount of available registers is different, as is the specification 
of which registers may be clobbered.

> OK, given a patch to have just one version of the cpuid call, would you
> be willing to take the risk of finding out which users it breaks for?
> I'll send patches to revert and restore correct behaviour for 32-bit if
> that does happen.
>   

This is in upstream qemu so it's not my call but I wouldn't recommend 
breaking the build when a trivial one liner is possible.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.