iommu/dart: Fix apple_dart_device_group for PCI groups

pci_device_group() can return an already existing IOMMU group if the PCI
device's pagetables have to be shared with another one due to bus
toplogy, isolation features and/or DMA alias quirks.
apple_dart_device_group() however assumes that the group has just been
created and overwrites its iommudata which will eventually lead to
apple_dart_release_group leaving stale entries in sid2group.
Fix that by merging the iommudata if the returned group already exists.

Fixes: f0b636804c7c ("iommu/dart: Clear sid2group entry when a group is freed")
Signed-off-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Link: https://lore.kernel.org/r/20230128113532.94651-1-sven@svenpeter.dev
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
index 42666617803dd52bdf9020a5f5cbd70ae0069c7d..1fc64a42c890f0b71a6083218798f446441e0389 100644 (file)
--- a/drivers/iommu/apple-dart.c
+++ b/drivers/iommu/apple-dart.c
@@ -835,6 +835,29 @@ static void apple_dart_release_group(void *iommu_data)
        mutex_unlock(&apple_dart_groups_lock);
 }
 
+static int apple_dart_merge_master_cfg(struct apple_dart_master_cfg *dst,
+                                      struct apple_dart_master_cfg *src)
+{
+       /*
+        * We know that this function is only called for groups returned from
+        * pci_device_group and that all Apple Silicon platforms never spread
+        * PCIe devices from the same bus across multiple DARTs such that we can
+        * just assume that both src and dst only have the same single DART.
+        */
+       if (src->stream_maps[1].dart)
+               return -EINVAL;
+       if (dst->stream_maps[1].dart)
+               return -EINVAL;
+       if (src->stream_maps[0].dart != dst->stream_maps[0].dart)
+               return -EINVAL;
+
+       bitmap_or(dst->stream_maps[0].sidmap,
+                 dst->stream_maps[0].sidmap,
+                 src->stream_maps[0].sidmap,
+                 dst->stream_maps[0].dart->num_streams);
+       return 0;
+}
+
 static struct iommu_group *apple_dart_device_group(struct device *dev)
 {
        int i, sid;
@@ -876,14 +899,28 @@ static struct iommu_group *apple_dart_device_group(struct device *dev)
        if (!group)
                goto out;
 
-       group_master_cfg = kmemdup(cfg, sizeof(*group_master_cfg), GFP_KERNEL);
-       if (!group_master_cfg) {
-               iommu_group_put(group);
-               goto out;
-       }
+       group_master_cfg = iommu_group_get_iommudata(group);
+       if (group_master_cfg) {
+               int ret;
 
-       iommu_group_set_iommudata(group, group_master_cfg,
-               apple_dart_release_group);
+               ret = apple_dart_merge_master_cfg(group_master_cfg, cfg);
+               if (ret) {
+                       dev_err(dev, "Failed to merge DART IOMMU grups.\n");
+                       iommu_group_put(group);
+                       res = ERR_PTR(ret);
+                       goto out;
+               }
+       } else {
+               group_master_cfg = kmemdup(cfg, sizeof(*group_master_cfg),
+                                          GFP_KERNEL);
+               if (!group_master_cfg) {
+                       iommu_group_put(group);
+                       goto out;
+               }
+
+               iommu_group_set_iommudata(group, group_master_cfg,
+                       apple_dart_release_group);
+       }
 
        for_each_stream_map(i, cfg, stream_map)
                for_each_set_bit(sid, stream_map->sidmap, stream_map->dart->num_streams)