[SRU][PATCH 1/1][X/aws] iommu/vt-d: Gracefully handle DMAR units with no supported address widths

[Andrea Righi]

From: David Woodhouse <dwmw at amazon.co.uk>

BugLink: https://bugs.launchpad.net/bugs/1913739

Instead of bailing out completely, such a unit can still be used for
interrupt remapping.

Signed-off-by: David Woodhouse <dwmw at amazon.co.uk>
Reviewed-by: Lu Baolu <baolu.lu at linux.intel.com>
Link: https://lore.kernel.org/linux-iommu/549928db2de6532117f36c9c810373c14cf76f51.camel@infradead.org/
Signed-off-by: Joerg Roedel <jroedel at suse.de>
(backported from c40aaaac1018ff1382f2d35df5129a6bcea3df6b)
Signed-off-by: Andrea Righi <andrea.righi at canonical.com>ko
---
 drivers/iommu/dmar.c | 45 ++++++++++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 00169c9eb3eed..78174f2f9fafb 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1012,8 +1012,8 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 {
 	struct intel_iommu *iommu;
 	u32 ver, sts;
-	int agaw = 0;
-	int msagaw = 0;
+	int agaw = -1;
+	int msagaw = -1;
 	int err;
 
 	if (!drhd->reg_base_addr) {
@@ -1038,17 +1038,28 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 	}
 
 	err = -EINVAL;
-	agaw = iommu_calculate_agaw(iommu);
-	if (agaw < 0) {
-		pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
-			iommu->seq_id);
-		goto err_unmap;
+	if (cap_sagaw(iommu->cap) == 0) {
+		pr_info("%s: No supported address widths. Not attempting DMA translation.\n",
+			iommu->name);
+		drhd->ignored = 1;
 	}
-	msagaw = iommu_calculate_max_sagaw(iommu);
-	if (msagaw < 0) {
-		pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
-			iommu->seq_id);
-		goto err_unmap;
+
+	if (!drhd->ignored) {
+		agaw = iommu_calculate_agaw(iommu);
+		if (agaw < 0) {
+			pr_err("Cannot get a valid agaw for iommu (seq_id = %d)\n",
+			       iommu->seq_id);
+			drhd->ignored = 1;
+		}
+	}
+	if (!drhd->ignored) {
+		msagaw = iommu_calculate_max_sagaw(iommu);
+		if (msagaw < 0) {
+			pr_err("Cannot get a valid max agaw for iommu (seq_id = %d)\n",
+			       iommu->seq_id);
+			drhd->ignored = 1;
+			agaw = -1;
+		}
 	}
 	iommu->agaw = agaw;
 	iommu->msagaw = msagaw;
@@ -1077,7 +1088,12 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
 	drhd->iommu = iommu;
 
-	if (intel_iommu_enabled)
+	/*
+	 * This is only for hotplug; at boot time intel_iommu_enabled won't
+	 * be set yet. When intel_iommu_init() runs, it registers the units
+	 * present at boot time, then sets intel_iommu_enabled.
+	 */
+	if (intel_iommu_enabled && !drhd->ignored)
 		iommu->iommu_dev = iommu_device_create(NULL, iommu,
 						       intel_iommu_groups,
 						       "%s", iommu->name);
@@ -1095,7 +1111,8 @@ error:
 
 static void free_iommu(struct intel_iommu *iommu)
 {
-	iommu_device_destroy(iommu->iommu_dev);
+	if (intel_iommu_enabled && iommu->iommu_dev)
+		iommu_device_destroy(iommu->iommu_dev);
 
 	if (iommu->irq) {
 		if (iommu->pr_irq) {
-- 
2.29.2