From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH 1/5] Protect irq_sources_bitmap by kvm->lock instead of kvm->irq_lock Date: Mon, 13 Jul 2009 17:39:41 +0300 Message-ID: <20090713143941.GT28046@redhat.com> References: <1247476355-27284-1-git-send-email-gleb@redhat.com> <1247476355-27284-2-git-send-email-gleb@redhat.com> <4A5B44AE.4000407@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, avi@redhat.com, mtosatti@redhat.com To: Gregory Haskins Return-path: Received: from mx2.redhat.com ([66.187.237.31]:36269 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756045AbZGMOjp (ORCPT ); Mon, 13 Jul 2009 10:39:45 -0400 Content-Disposition: inline In-Reply-To: <4A5B44AE.4000407@gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Jul 13, 2009 at 10:29:02AM -0400, Gregory Haskins wrote: > Gleb Natapov wrote: > > It is already protected by kvm->lock on device assignment path. Just > > take the same lock in the PIT code. > > > > Signed-off-by: Gleb Natapov > > --- > > arch/x86/kvm/i8254.c | 2 ++ > > virt/kvm/irq_comm.c | 8 ++++---- > > 2 files changed, 6 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c > > index 05e00a8..e1b9016 100644 > > --- a/arch/x86/kvm/i8254.c > > +++ b/arch/x86/kvm/i8254.c > > @@ -596,7 +596,9 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags) > > if (!pit) > > return NULL; > > > > + mutex_lock(&kvm->lock); > > pit->irq_source_id = kvm_request_irq_source_id(kvm); > > + mutex_unlock(&kvm->lock); > > if (pit->irq_source_id < 0) { > > kfree(pit); > > return NULL; > > diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c > > index 6c57e46..ce8fcd3 100644 > > --- a/virt/kvm/irq_comm.c > > +++ b/virt/kvm/irq_comm.c > > @@ -210,7 +210,8 @@ int kvm_request_irq_source_id(struct kvm *kvm) > > unsigned long *bitmap = &kvm->arch.irq_sources_bitmap; > > int irq_source_id; > > > > - mutex_lock(&kvm->irq_lock); > > + WARN_ON(!mutex_is_locked(&kvm->lock)); > > > > Shouldn't this be fatal? (e.g. BUG_ON). I know the usage between > BUG/WARN is controversial, but it seems to me that something is > completely broken if you expect it to be locked and its not. Might as > well fail the system, IMO. > Well I don't really care but we have WARN_ON() in the code currently. Besides the chances are good that even without locking around this function nothing will break, so why kill host kernel? > Regards, > -Greg > > > + > > irq_source_id = find_first_zero_bit(bitmap, > > sizeof(kvm->arch.irq_sources_bitmap)); > > > > @@ -221,7 +222,6 @@ int kvm_request_irq_source_id(struct kvm *kvm) > > > > ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID); > > set_bit(irq_source_id, bitmap); > > - mutex_unlock(&kvm->irq_lock); > > > > return irq_source_id; > > } > > @@ -230,9 +230,10 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id) > > { > > int i; > > > > + /* during vm destruction this function is called without locking */ > > + WARN_ON(!mutex_is_locked(&kvm->lock) && atomic_read(&kvm->users_count)); > > ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID); > > > > - mutex_lock(&kvm->irq_lock); > > if (irq_source_id < 0 || > > irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) { > > printk(KERN_ERR "kvm: IRQ source ID out of range!\n"); > > @@ -241,7 +242,6 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id) > > for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++) > > clear_bit(irq_source_id, &kvm->arch.irq_states[i]); > > clear_bit(irq_source_id, &kvm->arch.irq_sources_bitmap); > > - mutex_unlock(&kvm->irq_lock); > > } > > > > void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq, > > > > -- Gleb.