linux-kernel - [PATCH v2 33/59] KVM: x86: Skip IOMMU IRTE updates if there's no old or new vCPU being targeted

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Message-ID: <20250523010004.3240643-34-seanjc@google.com>
Date: Thu, 22 May 2025 17:59:38 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: 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: 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 v2 33/59] KVM: x86: Skip IOMMU IRTE updates if there's no old
 or new vCPU being targeted

Don't "reconfigure" an IRTE into host controlled mode when it's already in
the state, i.e. if KVM's GSI routing changes but the IRQ wasn't and still
isn't being posted to a vCPU.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/irq.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 3a0f28e98429..67fc8901d15f 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -542,6 +542,9 @@ static int kvm_pi_update_irte(struct kvm_kernel_irqfd *irqfd,
 			vcpu = NULL;
 	}
 
+	if (!irqfd->irq_bypass_vcpu && !vcpu)
+		return 0;
+
 	r = kvm_x86_call(pi_update_irte)(irqfd, irqfd->kvm, host_irq, irqfd->gsi,
 					 vcpu, irq.vector);
 	if (r) {
-- 
2.49.0.1151.ga128411c76-goog