KVM: VMX: Stop walking list of routing table entries when updating IRTE

Now that KVM provides the to-be-updated routing entry, stop walking the
routing table to find that entry.  KVM, via setup_routing_entry() and
sanity checked by kvm_get_msi_route(), disallows having a GSI configured
to trigger multiple MSIs, i.e. the for-loop can only process one entry.

Link: https://lore.kernel.org/r/20250611224604.313496-26-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index d4826a6b674f88a05d2e82c944e87ac3e4ed2da3..e59eae11f476f2423e93accef3c876c6a2ee38b0 100644 (file)
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -302,78 +302,44 @@ int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
                       unsigned int host_irq, uint32_t guest_irq,
                       struct kvm_kernel_irq_routing_entry *new)
 {
-       struct kvm_kernel_irq_routing_entry *e;
-       struct kvm_irq_routing_table *irq_rt;
-       bool enable_remapped_mode = true;
        struct kvm_lapic_irq irq;
        struct kvm_vcpu *vcpu;
        struct vcpu_data vcpu_info;
-       bool set = !!new;
-       int idx, ret = 0;
 
        if (!vmx_can_use_vtd_pi(kvm))
                return 0;
 
-       idx = srcu_read_lock(&kvm->irq_srcu);
-       irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
-       if (guest_irq >= irq_rt->nr_rt_entries ||
-           hlist_empty(&irq_rt->map[guest_irq])) {
-               pr_warn_once("no route for guest_irq %u/%u (broken user space?)\n",
-                            guest_irq, irq_rt->nr_rt_entries);
-               goto out;
-       }
-
-       hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
-               if (e->type != KVM_IRQ_ROUTING_MSI)
-                       continue;
-
-               WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
-
-               /*
-                * VT-d PI cannot support posting multicast/broadcast
-                * interrupts to a vCPU, we still use interrupt remapping
-                * for these kind of interrupts.
-                *
-                * For lowest-priority interrupts, we only support
-                * those with single CPU as the destination, e.g. user
-                * configures the interrupts via /proc/irq or uses
-                * irqbalance to make the interrupts single-CPU.
-                *
-                * We will support full lowest-priority interrupt later.
-                *
-                * In addition, we can only inject generic interrupts using
-                * the PI mechanism, refuse to route others through it.
-                */
-
-               kvm_set_msi_irq(kvm, e, &irq);
-               if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu) ||
-                   !kvm_irq_is_postable(&irq))
-                       continue;
-
-               vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu));
-               vcpu_info.vector = irq.vector;
-
-               trace_kvm_pi_irte_update(host_irq, vcpu->vcpu_id, e->gsi,
-                               vcpu_info.vector, vcpu_info.pi_desc_addr, set);
+       /*
+        * VT-d PI cannot support posting multicast/broadcast
+        * interrupts to a vCPU, we still use interrupt remapping
+        * for these kind of interrupts.
+        *
+        * For lowest-priority interrupts, we only support
+        * those with single CPU as the destination, e.g. user
+        * configures the interrupts via /proc/irq or uses
+        * irqbalance to make the interrupts single-CPU.
+        *
+        * We will support full lowest-priority interrupt later.
+        *
+        * In addition, we can only inject generic interrupts using
+        * the PI mechanism, refuse to route others through it.
+        */
+       if (!new || new->type != KVM_IRQ_ROUTING_MSI)
+               goto do_remapping;
 
-               if (!set)
-                       continue;
+       kvm_set_msi_irq(kvm, new, &irq);
 
-               enable_remapped_mode = false;
+       if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu) ||
+           !kvm_irq_is_postable(&irq))
+               goto do_remapping;
 
-               ret = irq_set_vcpu_affinity(host_irq, &vcpu_info);
-               if (ret < 0) {
-                       printk(KERN_INFO "%s: failed to update PI IRTE\n",
-                                       __func__);
-                       goto out;
-               }
-       }
+       vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu));
+       vcpu_info.vector = irq.vector;
 
-       if (enable_remapped_mode)
-               ret = irq_set_vcpu_affinity(host_irq, NULL);
+       trace_kvm_pi_irte_update(host_irq, vcpu->vcpu_id, guest_irq,
+                                vcpu_info.vector, vcpu_info.pi_desc_addr, true);
 
-       ret = 0;
-out:
-       srcu_read_unlock(&kvm->irq_srcu, idx);
-       return ret;
+       return irq_set_vcpu_affinity(host_irq, &vcpu_info);
+do_remapping:
+       return irq_set_vcpu_affinity(host_irq, NULL);
 }