Re: [PATCH v3 0/9] vfio: Fix release ordering races and use driver_override

Auger Eric
2017-06-26T07:31:17Z

Hi Alex,

On 20/06/2017 17:47, Alex Williamson wrote:
> v3:
>
> * Fix Alexey's nit in 2/, which becomes a bug in 3/. I posted the
> intended correction for this, but 0-day builds broke on it and I'd
> like to be sure we get all the automated testing possible, so v3.
> Added Alexey's Rb.

I tested non regression with vfio-platform.

"vfio: Use driver_override to avert binding to compromising drivers"
modality was tested with vfio-pci on aarch64 AMD Overdrive system (2 igb
PFs in the same group).

Feel free to add my Tested-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

>
> Thanks,
>
> Alex
>
> v2:
>
> * Added received acks and reviews, thanks!
> * Rebased and resolved conflict in patch 2/, dropped reviews due
> to changes and added Alexey to cc as spapr code is moved too
> * Added stable tag for patches 1-3
> * Resolved comment typo Eric noted in patch 1
> * Split AMBA out to patches 8 & 9 as Eric noted amba_bustype is
> not exported. These can be separate follow-up patches if delayed
>
> Please re-ack/review patch 2. Eric, I'm happy to add your Tested-by
> to the whole series if appropriate as well. Thanks,
>
> Alex
>
>
> v1:
>
> VM hotplug testing reveals a number of races in the vfio device,
> group, container shutdown path, some attributed to libvirt's ask/take
> unplug behavior and some long standing with groups potentially
> composed of multiple devices, where each device can be independently
> bound to drivers. Libvirt's ask/take behavior is a result of the
> asynchronous nature of PCI hotplug, libvirt registers a hot-unplug
> request (ask), which is acknowledged almost immediately and then
> proceeds to try to unbind the device from the vfio bus driver (take).
> This sets us off on racing paths where we allow the device to be
> released from the group much like would happen in groups with multiple
> devices, while the group and container are torn down separately.
> These races are addressed in the first 3 patches of this series.
>
> The long standing issue with removing devices from in-use groups is
> that we feel that the system is compromised if we allow user and host
> devices within the same non-isolated group. This triggers a BUG_ON
> when we detect this condition after the rogue driver binding. Since
> that code was put in place we've added driver_override support for
> all of the physical buses supported by vfio, giving us a way to block
> binding to such compromising drivers. We finally enable that in the
> latter 4 patches of this series, minding that we need to allow
> re-binding to non-compromising drivers, and also noting that a small
> synchronization stall is effective in eliminating the need for this
> blocking in the more common singleton device group case.
>
> Reviews, comments, and acks appreciated. Thanks,
>
> Alex
>
> ---
>
> Alex Williamson (9):
> vfio: Fix group release deadlock
> kvm-vfio: Decouple only when we match a group
> vfio: New external user group/file match
> iommu: Add driver-not-bound notification
> vfio: Create interface for vfio bus drivers to register
> vfio: Register pci, platform, amba, and mdev bus drivers
> vfio: Use driver_override to avert binding to compromising drivers
> amba: Export amba_bustype
> vfio: Add AMBA driver_override support
>
>
> drivers/amba/bus.c | 1
> drivers/iommu/iommu.c | 3
> drivers/vfio/mdev/vfio_mdev.c | 13 ++
> drivers/vfio/pci/vfio_pci.c | 7 +
> drivers/vfio/platform/vfio_amba.c | 24 +++
> drivers/vfio/platform/vfio_platform.c | 24 +++
> drivers/vfio/vfio.c | 252 ++++++++++++++++++++++++++++++++-
> include/linux/iommu.h | 1
> include/linux/vfio.h | 5 +
> virt/kvm/vfio.c | 40 +++--
> 10 files changed, 344 insertions(+), 26 deletions(-)
>