Patch f21916ec4826 ("s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated") introduced a change that results in a circular locking dependency when a Secure Execution guest that is configured with crypto devices is started. The problem resulted due to the fact that the patch moved the setting of the guest's AP masks within the protection of the matrix_dev->lock when the vfio_ap driver is notified that the KVM pointer has been set. Since it is not critical that setting/clearing of the guest's AP masks when the driver is notified, the masks will not be updated under the matrix_dev->lock. The lock is necessary for the setting/unsetting of the KVM pointer, however, so that will remain in place.
The dependency chain for the circular lockdep resolved by this patch is:
#2 vfio_ap_mdev_group_notifier: kvm->lock matrix_dev->lock
#1: handle_pqap: matrix_dev->lock kvm_vcpu_ioctl: vcpu->mutex
#0: kvm_s390_cpus_to_pv: vcpu->mutex kvm_vm_ioctl: kvm->lock
Tony Krowiak (1): s390/vfio-ap: fix circular lockdep when setting/clearing crypto masks
drivers/s390/crypto/vfio_ap_ops.c | 75 ++++++++++++++++++------------- 1 file changed, 45 insertions(+), 30 deletions(-)