From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH v6 5/5] KVM : VMX: Use posted interrupt to deliver
 virtual interrupt
Date: Tue, 19 Mar 2013 12:27:38 -0300
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On Tue, Mar 19, 2013 at 12:19:55PM -0300, Marcelo Tosatti wrote:
> See the previous argument: should never enter guest mode with PIR ON bit
> set. With logic above:  
> 
> context1				context2                      context3
> 					set_bit(PIR-1)                   
> 					r = pi_test_and_set_on()	set_bit(PIR-40)
> 					set_bit(KVM_REQ_EVENT)
> if (kvm_check_request(KVM_REQ_EVENT)	
>  if (test_and_clear_bit(on))
> 
>    kvm_apic_update_irr()						r = pi_test_and_set_on()
> 
> guest entry with PIR ON=1
> 
> 
> Thats the reason for unconditional clearing on guest entry: it is easy
> to verify its correct. I understand and agree the callback (and VMWRITE)
> is not nice.

Re: KVM_REQ_EVENT setting after set_bit(KVM_REQ_EVENT) assures no guest
entry with PIR ON=1.

Might be, would have to verify. Its trickier though. Maybe add a FIXME:
to the callback and remove it later.