Sorry to resurrect this thread. There's an srcu_synchronize_expedited call in kvm_set_irq_routing, so this lock might get held for a fairly long while. Wouldn't it be a better idea to check the irqchip mode? On Fri, Apr 7, 2017 at 1:50 AM, David Hildenbrand <david@xxxxxxxxxx> wrote: > Avoid races between KVM_SET_GSI_ROUTING and KVM_CREATE_IRQCHIP by taking > the kvm->lock when setting up routes. > > If KVM_CREATE_IRQCHIP fails, KVM_SET_GSI_ROUTING could have already set > up routes pointing at pic/ioapic, being silently removed already. > > Also, as a side effect, this patch makes sure that KVM_SET_GSI_ROUTING > and KVM_CAP_SPLIT_IRQCHIP cannot run in parallel. > > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > virt/kvm/kvm_main.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 88257b3..a80e400 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3082,8 +3082,11 @@ static long kvm_vm_ioctl(struct file *filp, > routing.nr * sizeof(*entries))) > goto out_free_irq_routing; > } > + /* avoid races with KVM_CREATE_IRQCHIP on x86 */ > + mutex_lock(&kvm->lock); > r = kvm_set_irq_routing(kvm, entries, routing.nr, > routing.flags); > + mutex_unlock(&kvm->lock); > out_free_irq_routing: > vfree(entries); > break; > -- > 2.9.3 >
