From: Sean Christopherson Date: Thu, 22 May 2025 23:52:13 +0000 (-0700) Subject: KVM: Initialize irqfd waitqueue callback when adding to the queue X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b5c543518ae9df8e99c63cd08a8b573f0141b31a;p=thirdparty%2Fkernel%2Fstable.git KVM: Initialize irqfd waitqueue callback when adding to the queue Initialize the irqfd waitqueue callback immediately prior to inserting the irqfd into the eventfd's waitqueue. Pre-initializing the state in a completely different context is all kinds of confusing, and incorrectly suggests that the waitqueue function needs to be initialize prior to vfs_poll(). Tested-by: K Prateek Nayak Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20250522235223.3178519-4-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index 614f81cd37c1..7b7c5269cf18 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -256,6 +256,13 @@ static void kvm_irqfd_register(struct file *file, wait_queue_head_t *wqh, struct kvm_irqfd_pt *p = container_of(pt, struct kvm_irqfd_pt, pt); struct kvm_kernel_irqfd *irqfd = p->irqfd; + /* + * Add the irqfd as a priority waiter on the eventfd, with a custom + * wake-up handler, so that KVM *and only KVM* is notified whenever the + * underlying eventfd is signaled. + */ + init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup); + add_wait_queue_priority(wqh, &irqfd->wait); } @@ -388,12 +395,6 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args) mutex_unlock(&kvm->irqfds.resampler_lock); } - /* - * Install our own custom wake-up handling so we are notified via - * a callback whenever someone signals the underlying eventfd - */ - init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup); - /* * Set the irqfd routing and add it to KVM's list before registering * the irqfd with the eventfd, so that the routing information is valid