Re: [RFC] hw/nvme: Use irqfd to send interrupts

[Jinhao Fan]

at 11:18 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:

> I think that is incorrect. QEMU has guest notifier emulation for the
> non-KVM (and non-MSI-X PCI) cases. When there is no irqfd support
> available, QEMU sets up a regular eventfd and calls
> virtio_queue_guest_notifier_read() when it becomes readable.

Thanks Stefan. I finally understand why there is a `with_irqfd` parameter
for virtio_queue_set_guest_notifier_fd_handler.

But if `with_irqfd` is false, it seems OK to directly call virtio_irq(). Why
still bother using an eventfd? Is it for interrupt batching?