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.

Link: https://lore.kernel.org/r/20250611224604.313496-37-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 5b3f721808d5968d3eb22e62ec91c73e44742516..ecebd150c2f7f980d009a783cd2c558d0a64f429 100644 (file)
--- 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) {