Tony Krowiak 21195eb038 s390/vfio-ap: introduce new mutex to control access to the KVM pointer ... The vfio_ap device driver registers for notification when the pointer to the KVM object for a guest is set. Recall that the KVM lock (kvm->lock) mutex must be taken outside of the matrix_dev->lock mutex to prevent the reporting by lockdep of a circular locking dependency (a.k.a., a lockdep splat): * see commit 0cc00c8d40 ("Fix circular lockdep when setting/clearing crypto masks") * see commit 86956e7076 ("replace open coded locks for VFIO_GROUP_NOTIFY_SET_KVM notification") With the introduction of support for hot plugging/unplugging AP devices passed through to a KVM guest, a new guests_lock mutex is introduced to ensure the proper locking order is maintained: struct ap_matrix_dev { ... struct mutex guests_lock; ... } The matrix_dev->guests_lock controls access to the matrix_mdev instances that hold the state for AP devices that have been passed through to a KVM guest. This lock must be held to control access to the KVM pointer (matrix_mdev->kvm) while the vfio_ap device driver is using it to plug/unplug AP devices passed through to the KVM guest. Keep in mind, the proper locking order must be maintained whenever dynamically updating a KVM guest's APCB to plug/unplug adapters, domains and control domains: 1. matrix_dev->guests_lock: required to use the KVM pointer - stored in a struct ap_matrix_mdev instance - to update a KVM guest's APCB 2. matrix_mdev->kvm->lock: required to update a guest's APCB 3. matrix_dev->mdevs_lock: required to access data stored in a struct ap_matrix_mdev instance. Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>		2022-07-19 16:18:10 +02:00
..
block	libnvdimm for 5.19	2022-05-27 15:49:30 -07:00
char	S390:	2022-05-26 14:20:14 -07:00
cio	Driver core changes for 5.19-rc1	2022-06-03 11:48:47 -07:00
crypto	s390/vfio-ap: introduce new mutex to control access to the KVM pointer	2022-07-19 16:18:10 +02:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2022-05-12 16:15:30 -07:00
scsi	scsi: zfcp: Fix failed recovery on gone remote port with non-NPIV FCP devices	2022-01-24 23:30:27 -05:00
virtio	virtio: harden vring IRQ	2022-05-31 12:45:10 -04:00
Makefile	s390: remove pointless drivers-y in drivers/s390/Makefile	2019-09-16 13:21:51 +02:00