linux-kernel - [PATCH v5 2/3] KVM: x86: Add a helper to deduplicate I/O APIC EOI interception logic

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Message-ID: <20250304013335.4155703-3-seanjc@google.com>
Date: Mon,  3 Mar 2025 17:33:34 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Kai Huang <kai.huang@...el.com>, xuyun <xuyun_xy.xy@...ux.alibaba.com>, 
	weizijie <zijie.wei@...ux.alibaba.com>
Subject: [PATCH v5 2/3] KVM: x86: Add a helper to deduplicate I/O APIC EOI
 interception logic

Extract the vCPU specific EOI interception logic for I/O APIC emulation
into a common helper for userspace and in-kernel emulation in anticipation
of optimizing the "pending EOI" case.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/ioapic.c   |  7 ++-----
 arch/x86/kvm/ioapic.h   |  2 ++
 arch/x86/kvm/irq_comm.c | 21 +++++++++++++++++----
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 995eb5054360..45dae2d5d2f1 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -296,11 +296,8 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu *vcpu, ulong *ioapic_handled_vectors)
 		    index == RTC_GSI) {
 			u16 dm = kvm_lapic_irq_dest_mode(!!e->fields.dest_mode);
 
-			if (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
-						e->fields.dest_id, dm) ||
-			    kvm_apic_pending_eoi(vcpu, e->fields.vector))
-				__set_bit(e->fields.vector,
-					  ioapic_handled_vectors);
+			kvm_scan_ioapic_irq(vcpu, e->fields.dest_id, dm,
+					    e->fields.vector, ioapic_handled_vectors);
 		}
 	}
 	spin_unlock(&ioapic->lock);
diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h
index 539333ac4b38..aa8cb4ac0479 100644
--- a/arch/x86/kvm/ioapic.h
+++ b/arch/x86/kvm/ioapic.h
@@ -120,4 +120,6 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu *vcpu,
 			   ulong *ioapic_handled_vectors);
 void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
 			    ulong *ioapic_handled_vectors);
+void kvm_scan_ioapic_irq(struct kvm_vcpu *vcpu, u32 dest_id, u16 dest_mode,
+			 u8 vector, unsigned long *ioapic_handled_vectors);
 #endif
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 866f84392797..14590d9c4a37 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -402,6 +402,21 @@ void kvm_arch_post_irq_routing_update(struct kvm *kvm)
 	kvm_make_scan_ioapic_request(kvm);
 }
 
+void kvm_scan_ioapic_irq(struct kvm_vcpu *vcpu, u32 dest_id, u16 dest_mode,
+			 u8 vector, unsigned long *ioapic_handled_vectors)
+{
+	/*
+	 * Intercept EOI if the vCPU is the target of the new IRQ routing, or
+	 * the vCPU has a pending IRQ from the old routing, i.e. if the vCPU
+	 * may receive a level-triggered IRQ in the future, or already received
+	 * level-triggered IRQ.  The EOI needs to be intercepted and forwarded
+	 * to I/O APIC emulation so that the IRQ can be de-asserted.
+	 */
+	if (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT, dest_id, dest_mode) ||
+	    kvm_apic_pending_eoi(vcpu, vector))
+		__set_bit(vector, ioapic_handled_vectors);
+}
+
 void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
 			    ulong *ioapic_handled_vectors)
 {
@@ -427,10 +442,8 @@ void kvm_scan_ioapic_routes(struct kvm_vcpu *vcpu,
 			if (!irq.trig_mode)
 				continue;
 
-			if (kvm_apic_match_dest(vcpu, NULL, APIC_DEST_NOSHORT,
-						irq.dest_id, irq.dest_mode) ||
-			     kvm_apic_pending_eoi(vcpu, irq.vector))
-				__set_bit(irq.vector, ioapic_handled_vectors);
+			kvm_scan_ioapic_irq(vcpu, irq.dest_id, irq.dest_mode,
+					    irq.vector, ioapic_handled_vectors);
 		}
 	}
 	srcu_read_unlock(&kvm->irq_srcu, idx);
-- 
2.48.1.711.g2feabab25a-goog