Re: [PATCH 3/8] KVM: Adds ability to preempt an executing VCPU

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Gregory Haskins wrote:
>>> index 059f074..0f6cc32 100644
>>> ---  a/drivers/kvm/kvm.h
>>> +++ b/drivers/kvm/kvm.h
>>> @@ - 329,6 +329,8 @@ struct kvm_vcpu_irq {
>>>  	struct kvm_irqdevice dev;
>>>  	int                  pending;
>>>  	int                  deferred;
>>> +	struct task_struct  *task;
>>> +	int                  guest_mode;
>>>   
>>>       
>> - >guest_mode can be folded into - >task, by specifying that - >task != 
>> NULL is equivalent to - >guest_mode != 0.  This will make the rest of the 
>> code easier to read.
>>     
>
> The problem with doing it this way is that its no longer possible to detect the optimizing condition of "irq.task != current" when injecting interrupts.  This means that userspace will be inadvertently sending itself a signal every time it injects interrupts, which IMHO is undesirable.
>
>   

I meant keeping ->task and dropping ->guest_mode.  Or did I 
misunderstand something?

>>>  
>>> +	vcpu- >irq.task = current;
>>> +	smp_wmb();
>>> +
>>>   
>>>       
>> This is best moved where - >guest_mode is set.
>>     
>
> I can do this, but its common to all platforms so I figured it was best to be out here?
>
>   

Well, it scatters the logic.  If we can merge guest_mode and task it's 
moot anyway.


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


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