From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH v3 3/4] x86, apicv: add virtual interrupt delivery support
Date: Wed, 5 Dec 2012 13:14:38 +0200
Message-ID: <20121205111438.GN19514@redhat.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Tian, Kevin" <kevin.tian@intel.com>
To: "Zhang, Yang Z" <yang.z.zhang@intel.com>
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On Wed, Dec 05, 2012 at 03:43:41AM +0000, Zhang, Yang Z wrote:
> >> @@ -5657,12 +5673,20 @@ static int vcpu_enter_guest(struct kvm_vcp=
u
> > *vcpu)
> >>  	}
> >> =20
> >>  	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
> >> +		/* update archtecture specific hints for APIC
> >> +		 * virtual interrupt delivery */
> >> +		if (kvm_x86_ops->update_irq)
> >> +			kvm_x86_ops->update_irq(vcpu);
> >> +
> >>  		inject_pending_event(vcpu);
> >> =20
> >>  		/* enable NMI/IRQ window open exits if needed */
> >>  		if (vcpu->arch.nmi_pending)
> >>  			kvm_x86_ops->enable_nmi_window(vcpu);
> >> -		else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
> >> +		else if (kvm_apic_vid_enabled(vcpu)) {
> >> +			if (kvm_cpu_has_extint(vcpu))
> >> +				kvm_x86_ops->enable_irq_window(vcpu);
> >=20
> > If RVI is non-zero, then interrupt window should not be enabled,
> > accordingly to 29.2.2:
> >=20
> > "If a virtual interrupt has been recognized (see Section 29.2.1), i=
t will
> > be delivered at an instruction boundary when the following conditio=
ns all
> > hold: (1) RFLAGS.IF =3D 1; (2) there is no blocking by STI; (3) the=
re is no
> > blocking by MOV SS or by POP SS; and (4) the =93interrupt-window ex=
iting=94
> > VM-execution control is 0."
> Right. Must check RVI here.
>=20
Why? We request interrupt window here because there is ExtINT interrupt
pending. ExtINT interrupt has a precedence over APIC interrupts (our
current code is incorrect!), so we want vmexit as soon as interrupts ar=
e
allowed to inject ExtINT and we do not want virtual interrupt to be
delivered. I think the (4) there is exactly for this situation.

--
			Gleb.