RE: [PATCH] KVM: IA64: Using CFLAGS_vcpu.o to compile vcpu.c

Avi Kivity wrote:
> Zhang, Xiantao wrote:
>> Avi Kivity wrote:
>> 
>>> Zhang, Xiantao wrote:
>>> 
>>>>> Can you provide more information on how this was only discovered
>>>>> now? Was there a change in mainline that removed support for
>>>>> EXTRA_CFLAGS?] 
>>>>> 
>>>>> 
>>>> It should be an old issue we didn't sense before.  To specify
>>>> single object's compile option, only CFLAGS can work in this case.
>>>> 
>>> How did we not notice the issue?  What is the effect of the missing
>>> flags? It seems like a critical problem that should prevent kvm
>>> from working at all, so I don't understand how it was discovered so
>>> late. 
>>> 
>> 
>> Once missing this flags, compiler can touch the fixed registers and
>> leads to faults. But fortunately,current gcc didn't use them for
>> optimizations, so we didn't find it before. But anyway it should be
>> a potential issue. Updated one, remove kernel's default range.  
>> 
>> 
> 
> Okay, so it worked by accident?

At least we didn't meet explict issue was caused by it. But anyway, it may bite us with the changes of compiler or compiler's configuration.  

>> Subject: [PATCH] KVM: ia64: Fix: Use CFLAGS_vcpu.o to compile vcpu.c
>> 
>> EXTRA_CFLAGS doesn't work for this case.Without this flag,
>> it may result in compiler touch fixed registers.
>> 
> 
> Applied, thanks.