[PATCH 6/6] iommu/s390: implement def_domain_type

[Matthew Rosato <mjrosato@linux.ibm.com>]

On s390, identity domains are only supported under certain virtualization
scenarios.  If iommu passthrough is requested but unavailable for a
device, ignore the request and instead fall back to dma-iommu with a
message.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
---
 drivers/iommu/s390-iommu.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
index 18979d8109b2..6906e1b5b1b0 100644
--- a/drivers/iommu/s390-iommu.c
+++ b/drivers/iommu/s390-iommu.c
@@ -462,6 +462,28 @@ static void s390_iommu_get_resv_regions(struct device *dev,
 	}
 }
 
+static int s390_iommu_def_domain_type(struct device *dev)
+{
+	struct zpci_dev *zdev = to_zpci_dev(dev);
+
+	/* If strict DMA is requested this takes priority */
+	if (iommu_dma_is_strict())
+		return IOMMU_DOMAIN_DMA;
+
+	/* DMA_FQ is the default unless passthrough is specified */
+	if (!iommu_default_passthrough())
+		return IOMMU_DOMAIN_DMA_FQ;
+
+	/* If passthrough specified, CLP must indicate it is allowed. */
+	if (zdev->rtr_avail)
+		return IOMMU_DOMAIN_IDENTITY;
+
+	/* If not allowed, fall back to using translation via DMA_FQ */
+	pr_info("Passthrough ignored, translation required for %s.\n",
+		pci_name(to_pci_dev(dev)));
+	return IOMMU_DOMAIN_DMA_FQ;
+}
+
 static struct iommu_device *s390_iommu_probe_device(struct device *dev)
 {
 	struct zpci_dev *zdev;
@@ -839,6 +861,7 @@ static const struct iommu_ops s390_iommu_ops = {
 	.device_group = generic_device_group,
 	.pgsize_bitmap = SZ_4K,
 	.get_resv_regions = s390_iommu_get_resv_regions,
+	.def_domain_type = s390_iommu_def_domain_type,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= s390_iommu_attach_device,
 		.map_pages	= s390_iommu_map_pages,
-- 
2.47.0