On Mon, Jan 09, 2023 at 03:10:36PM -0500, Matthew Rosato wrote:
> Currently it is possible that the final put of a KVM reference comes from
> vfio during its device close operation. This occurs while the vfio group
> lock is held; however, if the vfio device is still in the kvm device list,
> then the following call chain could result in a deadlock:
>
> kvm_put_kvm
> -> kvm_destroy_vm
> -> kvm_destroy_devices
> -> kvm_vfio_destroy
> -> kvm_vfio_file_set_kvm
> -> vfio_file_set_kvm
> -> group->group_lock/group_rwsem
>
> Avoid this scenario by adding kvm_put_kvm_async which will perform the
> kvm_destroy_vm asynchronously if the refcount reaches 0.
>
> Fixes: 421cfe6596f6 ("vfio: remove VFIO_GROUP_NOTIFY_SET_KVM")
> Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gvt/kvmgt.c | 6 +++++-
> drivers/s390/crypto/vfio_ap_ops.c | 7 ++++++-
> include/linux/kvm_host.h | 3 +++
> virt/kvm/kvm_main.c | 22 ++++++++++++++++++++++
> 4 files changed, 36 insertions(+), 2 deletions(-)
Why two patches?
It looks OK to me
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Jason
