Re: [PATCH 0/3] s390/vfio-ap: fix hang when mdev attached to guest is removed

From: Matthew Rosato
Date: Wed May 31 2023 - 11:06:01 EST

On 5/30/23 6:35 PM, Tony Krowiak wrote:
> When a user attempts to remove a vfio-ap mediated device attached to a
> guest, the operation hangs until the mdev's fd is closed by the guest
> (i.e., the hostdev is detached or the guest is shut down). This patch
> series provides kernel-side code that allows userspace to set up a
> communication channel that will allow the vfio_ap device driver to notify
> userspace when a request to release the mdev is received, so that userspace
> can close the mdev fd and avoid the hang. The patch series provides the
> following:
> 1. Introduces code to handle the VFIO_DEVICE_GET_IRQ_INFO and
> VFIO_DEVICE_SET_IRQS ioctl calls to set the eventfd_ctx for signaling a
> device request to userspace.
> 2. Wires up the VFIO bus driver callback to request a release of the mdev.
> When invoked, the vfio_ap device driver will use the eventfd_ctx set up
> in #1 to signal a request to userspace to release the mdev.

As to how this series eventually reaches master... It touches both s390 and vfio.

@Alex/@s390 maintainers -- I suggest it go through s390 given the diffstat, it's almost completely in s390 drivers code. However there is a uapi hit to vfio.h (in patch 1) that should get at least an ACK from Alex beforehand.