From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH v6 5/5] KVM : VMX: Use posted interrupt to deliver
 virtual interrupt
Date: Tue, 19 Mar 2013 18:10:48 +0200
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Cc: "Zhang, Yang Z" <yang.z.zhang@intel.com>,
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	"Zhang, Xiantao" <xiantao.zhang@intel.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
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On Tue, Mar 19, 2013 at 12:27:38PM -0300, Marcelo Tosatti wrote:
> 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.
We have time still. RTC series is not ready yet. I'll think hard and try
to poke holes in the logic in this patch and you do the same for what I
propose.

--
			Gleb.