memory: allow memory_region_register_iommu_notifier() to fail

Currently, when a notifier is attempted to be registered and its
flags are not supported (especially the MAP one) by the IOMMU MR,
we generally abruptly exit in the IOMMU code. The failure could be
handled more nicely in the caller and especially in the VFIO code.

So let's allow memory_region_register_iommu_notifier() to fail as
well as notify_flag_changed() callback.

All sites implementing the callback are updated. This patch does
not yet remove the exit(1) in the amd_iommu code.

in SMMUv3 we turn the warning message into an error message saying
that the assigned device would not work properly.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 16 insertions, 5 deletions

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 6e67043ee0..e499dc215b 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -288,10 +288,16 @@ typedef struct IOMMUMemoryRegionClass {
      * @iommu: the IOMMUMemoryRegion
      * @old_flags: events which previously needed to be notified
      * @new_flags: events which now need to be notified
+     *
+     * Returns 0 on success, or a negative errno; in particular
+     * returns -EINVAL if the new flag bitmap is not supported by the
+     * IOMMU memory region. In case of failure, the error object
+     * must be created
      */
-    void (*notify_flag_changed)(IOMMUMemoryRegion *iommu,
-                                IOMMUNotifierFlag old_flags,
-                                IOMMUNotifierFlag new_flags);
+    int (*notify_flag_changed)(IOMMUMemoryRegion *iommu,
+                               IOMMUNotifierFlag old_flags,
+                               IOMMUNotifierFlag new_flags,
+                               Error **errp);
     /* Called to handle memory_region_iommu_replay().
      *
      * The default implementation of memory_region_iommu_replay() is to
@@ -1079,13 +1085,18 @@ void memory_region_notify_one(IOMMUNotifier *notifier,
  * memory_region_register_iommu_notifier: register a notifier for changes to
  * IOMMU translation entries.
  *
+ * Returns 0 on success, or a negative errno otherwise. In particular,
+ * -EINVAL indicates that at least one of the attributes of the notifier
+ * is not supported (flag/range) by the IOMMU memory region. In case of error
+ * the error object must be created.
+ *
  * @mr: the memory region to observe
  * @n: the IOMMUNotifier to be added; the notify callback receives a
  *     pointer to an #IOMMUTLBEntry as the opaque value; the pointer
  *     ceases to be valid on exit from the notifier.
  */
-void memory_region_register_iommu_notifier(MemoryRegion *mr,
-                                           IOMMUNotifier *n);
+int memory_region_register_iommu_notifier(MemoryRegion *mr,
+                                          IOMMUNotifier *n, Error **errp);
 
 /**
  * memory_region_iommu_replay: replay existing IOMMU translations to