pseries/iommu: Ensure TCEs are cleared with non-huge DDW

There are now two kinds of DMA windows that might be presented by
PowerVM DDW support -- huge windows (that can map all of system memory
regardless of the LPAR configuration) and non-huge windows (which
can't). They are implemented slightly differently in PowerVM, and thus
have different characteristics. The most obvious is that slot isolate
doesn't clear the TCEs/window for us with non-huge windows. Thus, when a
DLPAR operation occurs on a slot using a non-huge window, TCEs are still
present (the notifier chain doesn't currently remove them explicitly)
and the DLPAR fails. Fix this by calling remove_ddw() first, which will
unmap the DDW TCEs.

Note: a corresponding change to drmgr is needed to actually successfully
DLPAR, such that the device-tree update (which causes the notifier chain
to fire) occurs before slot isolate.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index a55b685..b4bb9e1 100644 (file)
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -1296,6 +1296,7 @@ static int iommu_reconfig_notifier(struct notifier_block *nb, unsigned long acti
 
        switch (action) {
        case OF_RECONFIG_DETACH_NODE:
+               remove_ddw(np);
                if (pci && pci->iommu_table)
                        iommu_free_table(pci->iommu_table, np->full_name);
 
@@ -1308,16 +1309,6 @@ static int iommu_reconfig_notifier(struct notifier_block *nb, unsigned long acti
                        }
                }
                spin_unlock(&direct_window_list_lock);
-
-               /*
-                * Because the notifier runs after isolation of the
-                * slot, we are guaranteed any DMA window has already
-                * been revoked and the TCEs have been marked invalid,
-                * so we don't need a call to remove_ddw(np). However,
-                * if an additional notifier action is added before the
-                * isolate call, we should update this code for
-                * completeness with such a call.
-                */
                break;
        default:
                err = NOTIFY_DONE;