Re: [PATCH v3 0/1] vfio: remove VFIO_GROUP_NOTIFY_SET_KVM

Alex Williamson
2022-05-24T16:08:11Z

On Thu, 19 May 2022 14:33:10 -0400
Matthew Rosato <mjrosato@linux.ibm.com> wrote:

> As discussed in this thread:
>
> https://lore.kernel.org/kvm/20220516172734.GE1343366@nvidia.com/
>
> Let's remove VFIO_GROUP_NOTIFY_SET_KVM and instead assume the association
> has already been established prior to device_open. For the types today
> that need a KVM (GVT, vfio-ap) these will fail if a KVM is not found.
> Looking ahead, vfio-pci-zdev will optionally want the KVM association
> (enable hardware assists) but it will not be a hard requirement (still
> want to allow other, non-KVM userspace usage).
>
> This is built on top of vfio-next and tested with s390x-pci
> (zdev-kvm series) and vfio-ap (GVT changes are compile-tested only)
>
> Changes for v3:
> - merge branches under if (device->open_count == 1) (Kevin)
> - move device->open_count-- out from group_rwsem (Kevin)
> - drop null KVM check (Christoph)
> - remove extra kvm_{get,put}_kvm from vfio_ap_ops, it was already getting
> a reference (Jason)
> - Add comment about kvm reference in vfio.h (Jason)
> - Return -EINVAL if !kvm for vfio-ap (Tony)
>
> Changes for v2:
> - gvt no longer needs release_work, get rid of it (Christoph)
> - a few compile fixes for gvt
> - update commit to mention fixes gvt oops (Jason)
> - s/down_write/down_read/ in a few spots (Jason)
> - avoid kvm build dependency by holding group read lock over device
> open/close and put the onus on the driver to obtain a reference if
> it will actually use the kvm pointer. Document the requirement,
> use lockdep_assert to ensure lock is held during register_notifer;
> today all callers are from driver open_device.
>
> Matthew Rosato (1):
> vfio: remove VFIO_GROUP_NOTIFY_SET_KVM
>
> drivers/gpu/drm/i915/gvt/gtt.c | 4 +-
> drivers/gpu/drm/i915/gvt/gvt.h | 3 -
> drivers/gpu/drm/i915/gvt/kvmgt.c | 82 ++++++--------------------
> drivers/s390/crypto/vfio_ap_ops.c | 35 ++---------
> drivers/s390/crypto/vfio_ap_private.h | 3 -
> drivers/vfio/vfio.c | 83 ++++++++++-----------------
> include/linux/vfio.h | 6 +-
> 7 files changed, 57 insertions(+), 159 deletions(-)

Applied to vfio next branch for v5.19. Thanks,

Alex