iommu: Don't print warning when IOMMU driver only supports unmanaged domains

Print the warning about the fall-back to IOMMU_DOMAIN_DMA in
iommu_group_get_for_dev() only when such a domain was
actually allocated.

Otherwise the user will get misleading warnings in the
kernel log when the iommu driver used doesn't support
IOMMU_DOMAIN_DMA and IOMMU_DOMAIN_IDENTITY.

Fixes: fccb4e3b8ab09 ('iommu: Allow default domain type to be set on the kernel command line')
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 33a982e33716..109de67d5d72 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1105,10 +1105,12 @@ struct iommu_group *iommu_group_get_for_dev(struct device *dev)
 
                 dom = __iommu_domain_alloc(dev->bus, iommu_def_domain_type);
                 if (!dom && iommu_def_domain_type != IOMMU_DOMAIN_DMA) {
-                        dev_warn(dev,
-                                 "failed to allocate default IOMMU domain of type %u; falling back to IOMMU_DOMAIN_DMA",
-                                 iommu_def_domain_type);
                         dom = __iommu_domain_alloc(dev->bus, IOMMU_DOMAIN_DMA);
+                        if (dom) {
+                                dev_warn(dev,
+                                         "failed to allocate default IOMMU domain of type %u; falling back to IOMMU_DOMAIN_DMA",
+                                         iommu_def_domain_type);
+                        }
                 }
 
                 group->default_domain = dom;