Re: [RESEND 2][PATCH 4/4] Modify KVM to update guest time accounting.

[Avi Kivity <avi@qumranet.com>]

Laurent Vivier wrote:

  

>> But if we didn't get an interrupt in that time?
>>
>> We can clear it a bit later, after local_irq_enable() in __vcpu_run(). 
>> However we need a nop instruction first because "sti" keeps interrupts
>> disabled for one more instruction.
>>     
>
> IMHO, I think it is better to let kvm_guest_exit() empty (you can remove it, if
> you want):
>
> 1st case:
> - unset PF_VCPU in kvm_guest_exit(), all the tick is always for system time.
> Guest time is always 0.
>
> 1st case and half:
>
> - like 1st case but we move kvm_guest_exit() as you propose and the reason of
> the interrupt is the tick interrupt. The tick is for guest time only. I think
> the probability is very low.
>   

If the guest is executing for 10% of the time, the probability is 
exactly 10%, no?

> 2nd case:
> - don't unset PF_VCPU in kvm_guest_exit(), all the tick is for guest time.
>   

But then even execution in ->handle_exit() is accounted as guest time, 
which is wrong.



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