On Tuesday 12 May 2009 19:55:24 Marcelo Tosatti wrote: > On Tue, May 12, 2009 at 05:32:09PM +0800, Sheng Yang wrote: > > kvm_vm_ioctl_deassign_dev_irq() would potentially recursively get > > kvm->lock, because it called kvm_deassigned_irq() which implicit hold > > kvm->lock by calling deassign_host_irq(). > > > > Fix it by move kvm_deassign_irq() out of critial region. And add the > > missing lock for deassign_guest_irq(). > > > > Reported-by: Alex Williamson <[email protected]> > > Signed-off-by: Sheng Yang <[email protected]> > > --- > > virt/kvm/kvm_main.c | 14 +++++++------- > > 1 files changed, 7 insertions(+), 7 deletions(-) > > > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > > index 4d00942..3c69655 100644 > > --- a/virt/kvm/kvm_main.c > > +++ b/virt/kvm/kvm_main.c > > @@ -215,6 +215,8 @@ static void kvm_assigned_dev_ack_irq(struct > > kvm_irq_ack_notifier *kian) static void deassign_guest_irq(struct kvm > > *kvm, > > struct kvm_assigned_dev_kernel *assigned_dev) > > { > > + mutex_lock(&kvm->lock); > > + > > kvm_unregister_irq_ack_notifier(&assigned_dev->ack_notifier); > > assigned_dev->ack_notifier.gsi = -1; > > > > @@ -222,6 +224,8 @@ static void deassign_guest_irq(struct kvm *kvm, > > kvm_free_irq_source_id(kvm, assigned_dev->irq_source_id); > > assigned_dev->irq_source_id = -1; > > assigned_dev->irq_requested_type &= ~(KVM_DEV_IRQ_GUEST_MASK); > > + > > + mutex_unlock(&kvm->lock); > > } > > > > /* The function implicit hold kvm->lock mutex due to cancel_work_sync() > > */ @@ -558,20 +562,16 @@ static int kvm_vm_ioctl_deassign_dev_irq(struct > > kvm *kvm, struct kvm_assigned_irq > > *assigned_irq) > > { > > - int r = -ENODEV; > > struct kvm_assigned_dev_kernel *match; > > > > mutex_lock(&kvm->lock); > > - > > match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head, > > assigned_irq->assigned_dev_id); > > + mutex_unlock(&kvm->lock); > > assigned_dev list is protected by kvm->lock. So you could have another > ioctl adding to it at the same time you're searching.
Oh, yes... My fault... > Could either have a separate kvm->assigned_devs_lock, to protect > kvm->arch.assigned_dev_head (users are ioctls that manipulate it), or > change the IRQ injection to use a separate spinlock, kill the workqueue > and call kvm_set_irq from the assigned device interrupt handler. Peferred the latter, though needs more work. But the only reason for put a workqueue here is because kvm->lock is a mutex? I can't believe... If so, I think we had made a big mistake - we have to fix all kinds of racy problem caused by this, but finally find it's unnecessary... Maybe another reason is kvm_kick_vcpu(), but have already fixed by you. Continue to check the code... -- regards Yang, Sheng -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
