> From: Tian, Kevin > Sent: Friday, April 22, 2022 8:13 AM > > > From: Christoph Hellwig <hch@xxxxxx> > > Sent: Thursday, April 21, 2022 1:41 PM > > > > I can see why a specific error might be nice for some cases and am > > open to that, but as a simple transformation this already looks good: > > > > There is a slight semantics change together with patch7. > > Before patch7 the container must be attached before calling > KVM_DEV_VFIO_GROUP_ADD, otherwise vfio_group_get_external_user() > will fail. In this case the result of cache coherency for a group is > deterministic, either true or false. > > After patch7 vfio_group_get_external_user() is not called. It's possible > that KVM_DEV_VFIO_GROUP_ADD is called before a container is attached > by the group. In this case cache coherency of the group cannot be > determined at that point. I prefer to returning an error in this callback > so KVM can still fail adding the group, instead of letting the inaccurate > coherency info to bit the user in a much latter point... > More accurately: s/cache coherency/enforced coherency/ in above.
