[PATCH 5/6] iommu/amd: Fail probe on ATS configuration failure

[Pranjal Shrivastava <praan@google.com>]

Update the driver to call pci_prepare_ats() after checking if
pci_ats_supported() and fail the probe_device if pci_prepare_ats()
returns an error. Additionally, update pdev_enable_cap_ats() to WARN_ON()
a failure in pci_enable_ats().

Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/amd/iommu.c | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 4ef6024c5a4e..783f53cb8599 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -566,10 +566,17 @@ static inline int pdev_enable_cap_ats(struct pci_dev *pdev)
 	if (amd_iommu_iotlb_sup &&
 	    (dev_data->flags & AMD_IOMMU_DEVICE_FLAG_ATS_SUP)) {
 		ret = pci_enable_ats(pdev, PAGE_SHIFT);
-		if (!ret) {
-			dev_data->ats_enabled = 1;
-			dev_data->ats_qdep    = pci_ats_queue_depth(pdev);
-		}
+
+		/*
+		 * pci_enable_ats() should not fail here because earlier
+		 * checks have already verified support & config.
+		 */
+		if (WARN_ON(ret))
+			return ret;
+
+		dev_data->ats_enabled = 1;
+		dev_data->ats_qdep    = pci_ats_queue_depth(pdev);
+		ret = 0;
 	}
 
 	return ret;
@@ -2514,8 +2521,17 @@ static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 	else
 		dev_data->max_irqs = MAX_IRQS_PER_TABLE_512;
 
-	if (dev_is_pci(dev))
-		pci_prepare_ats(to_pci_dev(dev), PAGE_SHIFT);
+	if (dev_is_pci(dev)) {
+		struct pci_dev *pdev = to_pci_dev(dev);
+
+		if (pci_ats_supported(pdev)) {
+			ret = pci_prepare_ats(pdev, PAGE_SHIFT);
+			if (ret) {
+				iommu_dev = ERR_PTR(ret);
+				goto out_err;
+			}
+		}
+	}
 
 	return iommu_dev;
 
-- 
2.54.0.823.g6e5bcc1fc9-goog