[PATCH] iommu/vt-d: gracefully handle DMAR units with no supported address widths

[David Woodhouse]

From: David Woodhouse <d...@amazon.co.uk>

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

Signed-off-by: David Woodhouse <d...@amazon.co.uk>
---
 drivers/iommu/intel/dmar.c | 46 +++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
index 93e6345f3414..4420a759f095 100644
--- a/drivers/iommu/intel/dmar.c
+++ b/drivers/iommu/intel/dmar.c
@@ -1024,8 +1024,8 @@ 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) {
@@ -1050,17 +1050,28 @@ 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;
-       }
-       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 (cap_sagaw(iommu->cap) == 0) {
+               pr_info("%s: No supported address widths. Not attempting DMA 
translation.\n",
+                       iommu->name);
+               drhd->ignored = 1;
+       }
+
+       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;
@@ -1087,7 +1098,12 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
        raw_spin_lock_init(&iommu->register_lock);
 
-       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) {
                err = iommu_device_sysfs_add(&iommu->iommu, NULL,
                                             intel_iommu_groups,
                                             "%s", iommu->name);
@@ -1117,7 +1133,7 @@ static int alloc_iommu(struct dmar_drhd_unit *drhd)
 
 static void free_iommu(struct intel_iommu *iommu)
 {
-       if (intel_iommu_enabled) {
+       if (intel_iommu_enabled && iommu->iommu.ops) {
                iommu_device_unregister(&iommu->iommu);
                iommu_device_sysfs_remove(&iommu->iommu);
        }
-- 
2.17.1

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