powerpc/powernv/npu: Do not try invalidating 32bit table when 64bit table is enabled

aik · mpe · commit d41ce7b1bcc3 · 2018-03-27T23:44:57.000+11:00
GPUs and the corresponding NVLink bridges get different PEs as they
have separate translation validation entries (TVEs). We put these PEs
to the same IOMMU group so they cannot be passed through separately.
So the iommu_table_group_ops::set_window/unset_window for GPUs do set
tables to the NPU PEs as well which means that iommu_table's list of
attached PEs (iommu_table_group_link) has both GPU and NPU PEs linked.
This list is used for TCE cache invalidation.

The problem is that NPU PE has just a single TVE and can be programmed
to point to 32bit or 64bit windows while GPU PE has two (as any other
PCI device). So we end up having an 32bit iommu_table struct linked to
both PEs even though only the 64bit TCE table cache can be invalidated
on NPU. And a relatively recent skiboot detects this and prints
errors.

This changes GPU's iommu_table_group_ops::set_window/unset_window to
make sure that NPU PE is only linked to the table actually used by the
hardware. If there are two tables used by an IOMMU group, the NPU PE
will use the last programmed one which with the current use scenarios
is expected to be a 64bit one.

Signed-off-by: Alexey Kardashevskiy &lt;aik@ozlabs.ru&gt;
Signed-off-by: Michael Ellerman &lt;mpe@ellerman.id.au&gt;
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2681,14 +2681,23 @@ static struct pnv_ioda_pe *gpe_table_group_to_npe(
 static long pnv_pci_ioda2_npu_set_window(struct iommu_table_group *table_group,
 		int num, struct iommu_table *tbl)
 {
+	struct pnv_ioda_pe *npe = gpe_table_group_to_npe(table_group);
+	int num2 = (num == 0) ? 1 : 0;
 	long ret = pnv_pci_ioda2_set_window(table_group, num, tbl);
 
 	if (ret)
 		return ret;
 
-	ret = pnv_npu_set_window(gpe_table_group_to_npe(table_group), num, tbl);
-	if (ret)
+	if (table_group->tables[num2])
+		pnv_npu_unset_window(npe, num2);
+
+	ret = pnv_npu_set_window(npe, num, tbl);
+	if (ret) {
 		pnv_pci_ioda2_unset_window(table_group, num);
+		if (table_group->tables[num2])
+			pnv_npu_set_window(npe, num2,
+					table_group->tables[num2]);
+	}
 
 	return ret;
 }
@@ -2697,12 +2706,24 @@ static long pnv_pci_ioda2_npu_unset_window(
 		struct iommu_table_group *table_group,
 		int num)
 {
+	struct pnv_ioda_pe *npe = gpe_table_group_to_npe(table_group);
+	int num2 = (num == 0) ? 1 : 0;
 	long ret = pnv_pci_ioda2_unset_window(table_group, num);
 
 	if (ret)
 		return ret;
 
-	return pnv_npu_unset_window(gpe_table_group_to_npe(table_group), num);
+	if (!npe->table_group.tables[num])
+		return 0;
+
+	ret = pnv_npu_unset_window(npe, num);
+	if (ret)
+		return ret;
+
+	if (table_group->tables[num2])
+		ret = pnv_npu_set_window(npe, num2, table_group->tables[num2]);
+
+	return ret;
 }
 
 static void pnv_ioda2_npu_take_ownership(struct iommu_table_group *table_group)
