2017-04-07 10:50+0200, David Hildenbrand:
> Let's add a new mode and set it while we create the irqchip via
> KVM_CREATE_IRQCHIP and KVM_CAP_SPLIT_IRQCHIP.
>
> This mode will be used later to test if adding routes
> (in kvm_set_routing_entry()) is already allowed.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> @@ -3934,9 +3934,14 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
> goto split_irqchip_unlock;
> if (kvm->created_vcpus)
> goto split_irqchip_unlock;
> + kvm->arch.irqchip_mode = KVM_IRQCHIP_INIT_IN_PROGRESS;
> r = kvm_setup_empty_irq_routing(kvm);
> - if (r)
> + if (r) {
> + kvm->arch.irqchip_mode = KVM_IRQCHIP_NONE;
> + /* Pairs with smp_rmb() when reading irqchip_mode */
> + smp_wmb();
> goto split_irqchip_unlock;
> + }
> /* Pairs with irqchip_in_kernel. */
> smp_wmb();
> kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT;
> @@ -4024,8 +4029,12 @@ long kvm_arch_vm_ioctl(struct file *filp,
> goto create_irqchip_unlock;
> }
>
> + kvm->arch.irqchip_mode = KVM_IRQCHIP_INIT_IN_PROGRESS;
> r = kvm_setup_default_irq_routing(kvm);
> if (r) {
> + kvm->arch.irqchip_mode = KVM_IRQCHIP_NONE;
> + /* Pairs with smp_rmb() when reading irqchip_mode */
> + smp_wmb();
I think these two barriers are pointless.
KVM_IRQCHIP_INIT_IN_PROGRESS and KVM_IRQCHIP_NONE have the same result
for readers of irqchip mode and we don't even have a barrier after
setting KVM_IRQCHIP_INIT_IN_PROGRESS mode, so it looks weird.
I can remove them if you agree.
Thanks.
