iavf: Unregister vfio interrupt handler before interrup fd close

[sasinghal]

Unregister VFIO interrupt handler before the interrupt fd gets closed in case iavf_dev_init() returns an error.

dpdk creates a standalone thread named eal-intr-thread for processing interrupts for the PCI devices. The interrupt handler callbacks are registered by the VF driver(iavf, in this case).

When we do a PCI probe of the network interfaces, we register an interrupt handler, open a vfio-device fd(using ioctl) and an eventfd in dpdk. These interrupt sources are registered in a global linked list that the eal-intr-thread keeps iterating over for handling the interrupts. In our internal testing, we see eal-intr-thread crash in these two ways:

Error adding fd 660 epoll_ctl, Operation not permitted

or

Error adding fd 660 epoll_ctl, Bad file descriptor

epoll_ctl() returns EPERM if the target fd does not support poll. It returns EBADF when the epoll fd itself is closed or the target fd is closed.

When the first type of crash happens, we see that the fd 660 is anon_inode:[vfio-device] which does not support poll.

When the second type of crash happens, we could see from the fd map of the crashing process that the fd 660 was already closed.

We observed that these crashes were always accompanied by an error in iavf_dev_init() after rte_intr_callback_register() and iavf_enable_irq0() have already happened. In the error path, the intr_handle_fd was being closed but the interrupt handler wasn't being unregistered. The fix is to unregister the interrupt handle in the iavf_dev_init() error path.