[PATCH v3 36/62] KVM: x86: Don't update IRTE entries when old and new routes were !MSI

Sean Christopherson
2025-06-11T22:47:58Z

Skip the entirety of IRTE updates on a GSI routing change if neither the
old nor the new routing is for an MSI, i.e. if the neither routing setup
allows for posting to a vCPU. If the IRTE isn't already host controlled,
KVM has bigger problems.

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

diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
index 43e85ebc0d5b..4119c1e880e7 100644
--- a/arch/x86/kvm/irq.c
+++ b/arch/x86/kvm/irq.c
@@ -618,6 +618,10 @@ void kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
struct kvm_kernel_irq_routing_entry *old,
struct kvm_kernel_irq_routing_entry *new)
{
+ if (new->type != KVM_IRQ_ROUTING_MSI &&
+ old->type != KVM_IRQ_ROUTING_MSI)
+ return;
+
if (old->type == KVM_IRQ_ROUTING_MSI &&
new->type == KVM_IRQ_ROUTING_MSI &&
!memcmp(&old->msi, &new->msi, sizeof(new->msi)))
--
2.50.0.rc1.591.g9c95f17f64-goog