linux-kernel - Re: [PATCH v9 17/18] KVM: Update Posted-Interrupts Descriptor when vCPU is blocked

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Date:	Thu, 15 Oct 2015 20:13:11 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	David Matlack <dmatlack@...gle.com>, "Wu, Feng" <feng.wu@...el.com>
Cc:	"alex.williamson@...hat.com" <alex.williamson@...hat.com>,
	Joerg Roedel <joro@...tes.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	"eric.auger@...aro.org" <eric.auger@...aro.org>,
	kvm list <kvm@...r.kernel.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 17/18] KVM: Update Posted-Interrupts Descriptor when
 vCPU is blocked



On 15/10/2015 19:39, David Matlack wrote:
> But after spending more time reading the source code this morning I
> found that kvm_vcpu_check_block() eventually calls into
> vmx_sync_pir_to_irr(), which copies PIR to IRR and clears ON. And then
> apic_find_highest_irr() detects the pending posted interrupt.

Right.  And related to this, Feng, can you check if this is still
necessary on kvm/queue:

@@ -6518,6 +6523,20 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			kvm_vcpu_reload_apic_access_page(vcpu);
 	}
 
+	/*
+	 * KVM_REQ_EVENT is not set when posted interrupts are set by
+	 * VT-d hardware, so we have to update RVI unconditionally.
+	 */
+	if (kvm_lapic_enabled(vcpu)) {
+		/*
+		 * Update architecture specific hints for APIC
+		 * virtual interrupt delivery.
+		 */
+		if (kvm_x86_ops->hwapic_irr_update)
+			kvm_x86_ops->hwapic_irr_update(vcpu,
+				kvm_lapic_find_highest_irr(vcpu));
+	}
+
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
 		kvm_apic_accept_events(vcpu);
 		if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
@@ -6534,13 +6553,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			kvm_x86_ops->enable_irq_window(vcpu);
 
 		if (kvm_lapic_enabled(vcpu)) {
-			/*
-			 * Update architecture specific hints for APIC
-			 * virtual interrupt delivery.
-			 */
-			if (kvm_x86_ops->hwapic_irr_update)
-				kvm_x86_ops->hwapic_irr_update(vcpu,
-					kvm_lapic_find_highest_irr(vcpu));
 			update_cr8_intercept(vcpu);
 			kvm_lapic_sync_to_vapic(vcpu);
 		}


It may be obsolete now that we have the patch from Radim to set KVM_REQ_EVENT
in vmx_sync_pir_to_irr (http://permalink.gmane.org/gmane.linux.kernel/2057138).

Thanks,

Paolo
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