On Wed, 13 Feb 2019 11:18:21 +1100 Alexey Kardashevskiy <aik@xxxxxxxxx> wrote: > On 13/02/2019 07:52, Alex Williamson wrote: > > On Mon, 11 Feb 2019 18:49:17 +1100 > > Alexey Kardashevskiy <aik@xxxxxxxxx> wrote: > > > >> VFIO TCE IOMMU v2 owns IOMMU tables so when detach a IOMMU group from > >> a container, we need to unset those from a group so we call unset_window() > >> so do we unconditionally. We also unset tables when removing a DMA window > > > > Patch looks ok, but this first sentence trails off into a bit of a word > > salad. Care to refine a bit? Thanks, > > Fair comment, sorry for the salad. How about this? > > === > VFIO TCE IOMMU v2 owns IOMMU tables. When we detach an IOMMU group from > a container, we need to unset these tables from the group which we do by > calling unset_window(). We also unset tables when removing a DMA window > via the VFIO_IOMMU_SPAPR_TCE_REMOVE ioctl. > === Applied to vfio next branch with updated commit log and David's R-b. Thanks, Alex > > > >> via the VFIO_IOMMU_SPAPR_TCE_REMOVE ioctl. > >> > >> The window removal checks if the table actually exists (hidden inside > >> tce_iommu_find_table()) but the group detaching does not so the user > >> may see duplicating messages: > >> pci 0009:03 : [PE# fd] Removing DMA window #0 > >> pci 0009:03 : [PE# fd] Removing DMA window #1 > >> pci 0009:03 : [PE# fd] Removing DMA window #0 > >> pci 0009:03 : [PE# fd] Removing DMA window #1 > >> > >> At the moment this is not a problem as the second invocation > >> of unset_window() writes zeroes to the HW registers again and exits early > >> as there is no table. > >> > >> Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx> > >> --- > >> > >> When doing VFIO PCI hot unplug, first we remove the DMA window and > >> set container->tables[num] - this is a first couple of messages. > >> Then we detach the group and then we see another couple of the same > >> messages which confused myself. > >> --- > >> drivers/vfio/vfio_iommu_spapr_tce.c | 3 ++- > >> 1 file changed, 2 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c > >> index c424913..8dbb270 100644 > >> --- a/drivers/vfio/vfio_iommu_spapr_tce.c > >> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c > >> @@ -1235,7 +1235,8 @@ static void tce_iommu_release_ownership_ddw(struct tce_container *container, > >> } > >> > >> for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) > >> - table_group->ops->unset_window(table_group, i); > >> + if (container->tables[i]) > >> + table_group->ops->unset_window(table_group, i); > >> > >> table_group->ops->release_ownership(table_group); > >> } > > >
