Avihai Horon <avih...@nvidia.com> wrote: > Currently, if IOMMU of a VFIO container doesn't support dirty page > tracking, migration is blocked. This is because a DMA-able VFIO device > can dirty RAM pages without updating QEMU about it, thus breaking the > migration. > > However, this doesn't mean that migration can't be done at all. > In such case, allow migration and let QEMU VFIO code mark all pages > dirty. > > This guarantees that all pages that might have gotten dirty are reported > back, and thus guarantees a valid migration even without VFIO IOMMU > dirty tracking support. > > The motivation for this patch is the introduction of iommufd [1]. > iommufd can directly implement the /dev/vfio/vfio container IOCTLs by > mapping them into its internal ops, allowing the usage of these IOCTLs > over iommufd. However, VFIO IOMMU dirty tracking is not supported by > this VFIO compatibility API. > > This patch will allow migration by hosts that use the VFIO compatibility > API and prevent migration regressions caused by the lack of VFIO IOMMU > dirty tracking support. > > [1] > https://lore.kernel.org/kvm/0-v6-a196d26f289e+11787-iommufd_...@nvidia.com/ > > Signed-off-by: Avihai Horon <avih...@nvidia.com> > Reviewed-by: Cédric Le Goater <c...@redhat.com>
Reviewed-by: Juan Quintela <quint...@redhat.com> I know why you are doing this. But I think this should print a warning, error, somewhere. You are just dirtying all pages each time we arrive here. Even calling the featura "experimental" is an understatement. Later, Juan.
