Hi Michael, On 27/07/2017 03:30, Michael Roth wrote: > This series was motivated by the discussion in this thread: > > https://www.redhat.com/archives/libvir-list/2017-June/msg01370.html > > The issue this series addresses is that when libvirt unplugs a VFIO PCI > device, > it may attempt to bind the host device back to the host driver when QEMU emits > the DEVICE_DELETED event for the corresponding vfio-pci device. However, the > VFIO group FD is not actually cleaned up until vfio-pci device is *finalized* > by QEMU, whereas the event is emitted earlier during device_unparent. > Depending on the host device and how long certain operations like resetting > the > device might take, this can in result in libvirt trying to rebind the device > back to the host while it is still in use by VFIO, leading to host crashes or > other unexpected behavior. > > In particular, Mellanox CX4 adapters on PowerNV hosts might not be fully > quiesced by vfio-pci's finalize() routine until up to 6s after the > DEVICE_DELETED was emitted, leading to detach-device on the libvirt side > pretty > much always crashing the host. > > Implementing this change requires 2 prereqs to ensure the same information is > available when the DEVICE_DELETED is finally emitted: > > 1) Storing the path in the composition patch, which is addressed by PATCH 1, > which was plucked from another pending series from Greg Kurz: > > https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg07922.html > > since we are now "disconnected" at the time the event is emitted, and > > 2) Deferring qemu_opts_del of the DeviceState->QemuOpts till finalize, since > that is where DeviceState->id is stored. This was actually how it was > done in the past, so PATCH 2 simply reverts the change which moved it to > device_unparent. > > From there it's just a mechanical move of the event from device_unparent to > device_finalize. > > hw/core/qdev.c | 30 +++++++++++++++++++----------- > include/hw/qdev-core.h | 1 + > 2 files changed, 20 insertions(+), 11 deletions(-) > >
Tested-by: Eric Auger <eric.au...@redhat.com> Without the series I get the following warning when detaching a pci host dev from virt-manager: 2017-08-09T14:28:44.825925Z qemu-system-aarch64: Failed to remove group 53 from KVM VFIO device: No such file or directory as KVM_DEV_VFIO_GROUP_DEL returns -ENOENT due to the fact the fd for the VFIO group does not exist anymore as libvirt already started to unbind the device from vfio-pci at vfio_instance_finalize() time. With the series I don't see the message anymore. Thanks Eric