Messages in this thread | | | Date | Wed, 31 May 2023 10:48:24 -0400 | Subject | Re: [PATCH 0/3] s390/vfio-ap: fix hang when mdev attached to guest is removed | From | Matthew Rosato <> |
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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. > > > 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")
For the series:
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
I also did some testing using the companion qemu series at https://lore.kernel.org/qemu-devel/20230530225544.280031-1-akrowiak@linux.ibm.com
Before kernel+qemu changes: 1. mdevctl start -u <uuid>, where <uuid> references a vfio-ap mdev 2. start a qemu guest with <uuid> attached 3. mdvectl stop -u <uuid> 4. -mdevctl will now hang indefinitely; the mdev remains in-use by the guest- Note: detaching the device or powering off the guest will allow the mdevctl command to complete.
After kernel+qemu changes: 1. mdevctl start -u <uuid>, where <uuid> references a vfio-ap mdev 2. start a qemu guest with <uuid> attached 3. mdvectl stop -u <uuid> 4. -device is detached from the guest and stopped- 5. Using a libvirt that includes ebd004a03dbd I also verified that the mdev can be started again and re-attached to the running guest without error.
> > 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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