[PATCH v4 3/4] 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().

Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/amd/iommu.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 7f8b51c28a7e..195097365413 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -573,10 +573,17 @@ 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;
@@ -2458,10 +2465,12 @@ static void detach_device(struct device *dev)
 	mutex_unlock(&dev_data->mutex);
 }
 
-static void iommu_init_device_caps(struct iommu_dev_data *dev_data,
-				   struct device *dev,
-				   struct amd_iommu *iommu)
+static int iommu_init_device_caps(struct iommu_dev_data *dev_data,
+				  struct device *dev,
+				  struct amd_iommu *iommu)
 {
+	int ret;
+
 	if (FEATURE_NUM_INT_REMAP_SUP_2K(amd_iommu_efr2))
 		dev_data->max_irqs = MAX_IRQS_PER_TABLE_2K;
 	else
@@ -2470,7 +2479,7 @@ static void iommu_init_device_caps(struct iommu_dev_data *dev_data,
 	amd_iommu_set_pci_msi_domain(dev, iommu);
 
 	if (!dev_is_pci(dev))
-		return;
+		return 0;
 
 	/*
 	 * By default we use passthrough mode for IOMMUv2 capable device.
@@ -2493,7 +2502,13 @@ static void iommu_init_device_caps(struct iommu_dev_data *dev_data,
 					     pci_max_pasids(to_pci_dev(dev)));
 	}
 
-	pci_prepare_ats(to_pci_dev(dev), PAGE_SHIFT);
+	if (pci_ats_supported(to_pci_dev(dev))) {
+		ret = pci_prepare_ats(to_pci_dev(dev), PAGE_SHIFT);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 
 static struct iommu_device *amd_iommu_probe_device(struct device *dev)
@@ -2502,6 +2517,7 @@ static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 	struct amd_iommu *iommu;
 	struct iommu_dev_data *dev_data;
 	u16 devid;
+	int ret;
 
 	if (!lookup_device(dev, &iommu, &devid))
 		return ERR_PTR(-ENODEV);
@@ -2515,7 +2531,10 @@ static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 		return ERR_CAST(dev_data);
 	}
 
-	iommu_init_device_caps(dev_data, dev, iommu);
+	ret = iommu_init_device_caps(dev_data, dev, iommu);
+	if (ret)
+		return ERR_PTR(ret);
+
 	iommu_dev = &iommu->iommu;
 
 	/*
-- 
2.55.0.1003.g10538fe699-goog