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

Tony Krowiak
2023-05-30T22:35:48Z

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.

Note:
----
If a user subsequently attempts to restart the guest or re-attach the mdev,
the operation will fail with a message indicating the domain is already
active. This is a libvirt problem resolved with the following commit:

commit ebd004a03dbd ("security: do not remember/recall labels for VFIO
MDEVs")

Tony Krowiak (3):
vfio: ap: realize the VFIO_DEVICE_GET_IRQ_INFO ioctl
vfio: ap: realize the VFIO_DEVICE_SET_IRQS ioctl
s390/vfio-ap: Wire in the vfio_device_ops request callback

drivers/s390/crypto/vfio_ap_ops.c | 134 +++++++++++++++++++++++++-
drivers/s390/crypto/vfio_ap_private.h | 3 +
include/uapi/linux/vfio.h | 9 ++
3 files changed, 145 insertions(+), 1 deletion(-)

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2.31.1