The ACS requirement has been obscured in the current code and is only
known by certain individuals who happen to read the code. Print out a
warning with ACS path failure when ACS requirement is not met.

Signed-off-by: Sinan Kaya <redacted>
---
 drivers/iommu/iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index dbe7f65..049ee0a 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c

@@ -811,6 +811,9 @@ struct iommu_group *pci_device_group(struct device *dev)
 	if (IS_ERR(group))
 		return NULL;
 
+	if (pci_is_root_bus(bus))
+		dev_warn_once(&pdev->dev, "using shared group due to ACS path failure\n");
+
 	return group;
 }
 

-- 
1.9.1