linux-kernel - [PATCH v3 51/62] KVM: x86: WARN if IRQ bypass routing is updated without in-kernel local APIC

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Message-ID: <20250611224604.313496-53-seanjc@google.com>
Date: Wed, 11 Jun 2025 15:45:54 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Joerg Roedel <joro@...tes.org>, 
	David Woodhouse <dwmw2@...radead.org>, Lu Baolu <baolu.lu@...ux.intel.com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Sairaj Kodilkar <sarunkod@....com>, Vasant Hegde <vasant.hegde@....com>, 
	Maxim Levitsky <mlevitsk@...hat.com>, Joao Martins <joao.m.martins@...cle.com>, 
	Francesco Lavra <francescolavra.fl@...il.com>, David Matlack <dmatlack@...gle.com>
Subject: [PATCH v3 51/62] KVM: x86: WARN if IRQ bypass routing is updated
 without in-kernel local APIC

Yell if kvm_pi_update_irte() is reached without an in-kernel local APIC,
as kvm_arch_irqfd_allowed() should prevent attaching an irqfd and thus any
and all postable IRQs to an APIC-less VM.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/irq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 9c03a67fedbe..02efa7162252 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -517,8 +517,8 @@ static int kvm_pi_update_irte(struct kvm_kernel_irqfd *irqfd,
 	struct kvm_lapic_irq irq;
 	int r;
 
-	if (!irqchip_in_kernel(kvm) || WARN_ON_ONCE(!kvm_arch_has_irq_bypass()))
-		return 0;
+	if (WARN_ON_ONCE(!irqchip_in_kernel(kvm) || !kvm_arch_has_irq_bypass()))
+		return -EINVAL;
 
 	if (entry && entry->type == KVM_IRQ_ROUTING_MSI) {
 		kvm_set_msi_irq(kvm, entry, &irq);
-- 
2.50.0.rc1.591.g9c95f17f64-goog