Re: [v5 1/3] KVM: setup empty irq routing when create vm

[Paolo Bonzini]

On 4/17/26 11:36, Christian Borntraeger wrote:
> >          irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm- 
> > >irq_srcu,
> >                                          lockdep_is_held(&kvm- 
> > >irq_lock));
> >          if (irq_rt && gsi < irq_rt->nr_rt_entries) {  <---------
> Hmm, I guess I misread the code and the problem is likely not this.
> Let me have another look.

It makes sense anyway, together with a similar extra element in
kvm_set_irq_routing():

diff --git a/virt/kvm/irqchip.c b/virt/kvm/irqchip.c
index 462c70621247..c3e4fbbfed94 100644
--- a/virt/kvm/irqchip.c
+++ b/virt/kvm/irqchip.c
@@ -178,11 +178,9 @@ int kvm_set_irq_routing(struct kvm *kvm,
 	for (i = 0; i < nr; ++i) {
 		if (ue[i].gsi >= KVM_MAX_IRQ_ROUTES)
 			return -EINVAL;
-		nr_rt_entries = max(nr_rt_entries, ue[i].gsi);
+		nr_rt_entries = max(nr_rt_entries + 1, ue[i].gsi);
 	}
 
-	nr_rt_entries += 1;
-
 	new = kzalloc_flex(*new, map, nr_rt_entries, GFP_KERNEL_ACCOUNT);
 	if (!new)
 		return -ENOMEM;
@@ -246,11 +244,11 @@ int kvm_init_irq_routing(struct kvm *kvm)
 	struct kvm_irq_routing_table *new;
 	int chip_size;
 
-	new = kzalloc_flex(*new, map, 1, GFP_KERNEL_ACCOUNT);
+	new = kzalloc_flex(*new, map, 0, GFP_KERNEL_ACCOUNT);
 	if (!new)
 		return -ENOMEM;
 
-	new->nr_rt_entries = 1;
+	new->nr_rt_entries = 0;
 
 	chip_size = sizeof(int) * KVM_NR_IRQCHIPS * KVM_IRQCHIP_NUM_PINS;
 	memset(new->chip, -1, chip_size);

Paolo