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, 7 insertions, 2 deletions

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 2386b51..99de5f1 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -677,8 +677,9 @@ static void vhost_iommu_region_add(MemoryListener *listener,
                                          iommu_listener);
     struct vhost_iommu *iommu;
     Int128 end;
-    int iommu_idx;
+    int iommu_idx, ret;
     IOMMUMemoryRegion *iommu_mr;
+    Error *err = NULL;
 
     if (!memory_region_is_iommu(section->mr)) {
         return;
@@ -701,7 +702,11 @@ static void vhost_iommu_region_add(MemoryListener *listener,
     iommu->iommu_offset = section->offset_within_address_space -
                           section->offset_within_region;
     iommu->hdev = dev;
-    memory_region_register_iommu_notifier(section->mr, &iommu->n);
+    ret = memory_region_register_iommu_notifier(section->mr, &iommu->n, &err);
+    if (ret) {
+        error_report_err(err);
+        exit(1);
+    }
     QLIST_INSERT_HEAD(&dev->iommu_list, iommu, iommu_next);
     /* TODO: can replay help performance here? */
 }