[PATCH v4 1/4] iommu/amd: Refactor device probe and capability initialization

[Pranjal Shrivastava <praan@google.com>]

Restructure the device probe path to improve readability and prepare for
cleaner error handling. Refactor check_device() into lookup_device to
explicitly validate and return the amd_iommu ptr & devid. Refactor
iommu_init_device() to return the allocated dev_data. Consolidate all
PCI cap inits (MSI domains, PASID, ATS) into a new helper:
iommu_init_device_caps().

Suggested-by: Vasant Hegde <vasant.hegde@amd.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/amd/iommu.c | 117 +++++++++++++++++++-------------------
 1 file changed, 59 insertions(+), 58 deletions(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 4dc306a4b5c6..5e144a60c397 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -675,7 +675,8 @@ static void pdev_disable_caps(struct pci_dev *pdev)
  * This function checks if the driver got a valid device from the caller to
  * avoid dereferencing invalid pointers.
  */
-static bool check_device(struct device *dev)
+static bool lookup_device(struct device *dev,
+				struct amd_iommu **iommu_out, u16 *devid_out)
 {
 	struct amd_iommu_pci_seg *pci_seg;
 	struct amd_iommu *iommu;
@@ -690,7 +691,7 @@ static bool check_device(struct device *dev)
 	devid = PCI_SBDF_TO_DEVID(sbdf);
 
 	iommu = rlookup_amd_iommu(dev);
-	if (!iommu)
+	if (!iommu || !iommu->iommu.ops)
 		return false;
 
 	/* Out of our scope? */
@@ -698,47 +699,33 @@ static bool check_device(struct device *dev)
 	if (devid > pci_seg->last_bdf)
 		return false;
 
+	*iommu_out = iommu;
+	*devid_out = devid;
 	return true;
 }
 
-static int iommu_init_device(struct amd_iommu *iommu, struct device *dev)
+static struct iommu_dev_data *iommu_init_device(struct amd_iommu *iommu,
+						struct device *dev, u16 devid)
 {
 	struct iommu_dev_data *dev_data;
-	int devid, sbdf;
-
-	if (dev_iommu_priv_get(dev))
-		return 0;
 
-	sbdf = get_device_sbdf_id(dev);
-	if (sbdf < 0)
-		return sbdf;
-
-	devid = PCI_SBDF_TO_DEVID(sbdf);
 	dev_data = find_dev_data(iommu, devid);
 	if (!dev_data)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	dev_data->dev = dev;
 
 	/*
-	 * The dev_iommu_priv_set() needes to be called before setup_aliases.
+	 * The dev_iommu_priv_set() needs to be called before setup_aliases.
 	 * Otherwise, subsequent call to dev_iommu_priv_get() will fail.
 	 */
 	dev_iommu_priv_set(dev, dev_data);
 	setup_aliases(iommu, dev);
 
-	/*
-	 * By default we use passthrough mode for IOMMUv2 capable device.
-	 * But if amd_iommu=force_isolation is set (e.g. to debug DMA to
-	 * invalid address), we ignore the capability for the device so
-	 * it'll be forced to go into translation mode.
-	 */
-	if ((iommu_default_passthrough() || !amd_iommu_force_isolation) &&
-	    dev_is_pci(dev) && amd_iommu_gt_ppr_supported()) {
-		dev_data->flags = pdev_get_caps(to_pci_dev(dev));
-	}
+	/* Wait for DTE updates to go through */
+	iommu_completion_wait(iommu);
 
-	return 0;
+	return dev_data;
 }
 
 static void iommu_ignore_device(struct amd_iommu *iommu, struct device *dev)
@@ -2487,49 +2474,73 @@ 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)
+{
+	if (FEATURE_NUM_INT_REMAP_SUP_2K(amd_iommu_efr2))
+		dev_data->max_irqs = MAX_IRQS_PER_TABLE_2K;
+	else
+		dev_data->max_irqs = MAX_IRQS_PER_TABLE_512;
+
+	amd_iommu_set_pci_msi_domain(dev, iommu);
+
+	if (!dev_is_pci(dev))
+		return;
+
+	/*
+	 * By default we use passthrough mode for IOMMUv2 capable device.
+	 * But if amd_iommu=force_isolation is set (e.g. to debug DMA to
+	 * invalid address), we ignore the capability for the device so
+	 * it'll be forced to go into translation mode.
+	 */
+	if ((iommu_default_passthrough() || !amd_iommu_force_isolation) &&
+	    amd_iommu_gt_ppr_supported()) {
+		dev_data->flags = pdev_get_caps(to_pci_dev(dev));
+	}
+
+	/*
+	 * If IOMMU and device supports PASID then it will contain max
+	 * supported PASIDs, else it will be zero.
+	 */
+	if (amd_iommu_pasid_supported() &&
+	    pdev_pasid_supported(dev_data)) {
+		dev_data->max_pasids = min_t(u32, iommu->iommu.max_pasids,
+					     pci_max_pasids(to_pci_dev(dev)));
+	}
+
+	pci_prepare_ats(to_pci_dev(dev), PAGE_SHIFT);
+}
+
 static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 {
 	struct iommu_device *iommu_dev;
 	struct amd_iommu *iommu;
 	struct iommu_dev_data *dev_data;
-	int ret;
-
-	if (!check_device(dev))
-		return ERR_PTR(-ENODEV);
-
-	iommu = rlookup_amd_iommu(dev);
-	if (!iommu)
-		return ERR_PTR(-ENODEV);
+	u16 devid;
 
-	/* Not registered yet? */
-	if (!iommu->iommu.ops)
+	if (!lookup_device(dev, &iommu, &devid))
 		return ERR_PTR(-ENODEV);
 
 	if (dev_iommu_priv_get(dev))
 		return &iommu->iommu;
 
-	ret = iommu_init_device(iommu, dev);
-	if (ret) {
+	dev_data = iommu_init_device(iommu, dev, devid);
+	if (IS_ERR(dev_data)) {
 		dev_err(dev, "Failed to initialize - trying to proceed anyway\n");
-		iommu_dev = ERR_PTR(ret);
+		iommu_dev = ERR_CAST(dev_data);
 		iommu_ignore_device(iommu, dev);
 		goto out_err;
 	}
 
-	amd_iommu_set_pci_msi_domain(dev, iommu);
+	iommu_init_device_caps(dev_data, dev, iommu);
 	iommu_dev = &iommu->iommu;
 
 	/*
-	 * If IOMMU and device supports PASID then it will contain max
-	 * supported PASIDs, else it will be zero.
+	 * When DMA translation is unavailable return error so the iommu core
+	 * won't attempt domain attach for this device, while preserving its
+	 * rlookup entry for interrupt remapping.
 	 */
-	dev_data = dev_iommu_priv_get(dev);
-	if (amd_iommu_pasid_supported() && dev_is_pci(dev) &&
-	    pdev_pasid_supported(dev_data)) {
-		dev_data->max_pasids = min_t(u32, iommu->iommu.max_pasids,
-					     pci_max_pasids(to_pci_dev(dev)));
-	}
-
 	if (amd_iommu_pgtable == PD_MODE_NONE) {
 		pr_warn_once("%s: DMA translation not supported by iommu.\n",
 			     __func__);
@@ -2537,16 +2548,6 @@ static struct iommu_device *amd_iommu_probe_device(struct device *dev)
 		goto out_err;
 	}
 
-	iommu_completion_wait(iommu);
-
-	if (FEATURE_NUM_INT_REMAP_SUP_2K(amd_iommu_efr2))
-		dev_data->max_irqs = MAX_IRQS_PER_TABLE_2K;
-	else
-		dev_data->max_irqs = MAX_IRQS_PER_TABLE_512;
-
-	if (dev_is_pci(dev))
-		pci_prepare_ats(to_pci_dev(dev), PAGE_SHIFT);
-
 out_err:
 	return iommu_dev;
 }
-- 
2.55.0.1003.g10538fe699-goog