Re: questions about ack_intr_on_exit and preemption hooks

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

Stephane Eranian wrote:
> Avi,
>
> On Fri, Jul 13, 2007 at 09:53:36AM +0300, Avi Kivity wrote:
>   
>> Stephane Eranian wrote:
>>     
>>> Avi,
>>>
>>> A couple of months back, we had a discussion about PMU virtualization
>>> and the difficulty I encountered trying to catch the PMU interrupt
>>> vector in kvm on VM-exit. KVM does not set ack_intr_on_intr. Would
>>> you mind reminding me of the reason for this?
>>>
>>>   
>>>       
>> If we ack the interrupt, we have to dispatch it ourselves, most likely
>> by faking an 'int $xx' instruction.
>>
>> By not acking the interrupt, we allow it do be delivered through the
>> host IDT whether we are in guest mode or not.
>>
>>     
> Doesn't that assume that any interrupt generated by the guest has a
> host IDT entry?
>
>   

Right now we don't allow the guest access to the hardware, so the guest 
can't generate any interrupt.

> On a related issue, you set NMI_EXITING. Why is that? Assuming the
> guest does not use the NMI watchdog. Are you doing this to ensure
> that the host NMI watchdog keeps on going while you're executing 
> in the guest?
>   

Yes.  Or oprofile.


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


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