On 25.04.2017 00:39, Steve Rutherford wrote: > 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? > We could maybe check for kvm->arch.irqchip_mode == KVM_IRQCHIP_NONE here under lock instead of in the function itself. Maybe we then even don't need patch NR 2. Will have a look! Thanks! > 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 >> -- Thanks, David
