[Qemu-devel] [PATCH 2/2] hw/arm/smmuv3: Implement dummy replay

[Eric Auger <eric.auger@redhat.com>]

On ARM we currently do not support VFIO-PCI devices protected
by the IOMMU. Any attempt to run such use case results in this
kind of warning:

"-device vfio-pci,host=0004:01:00.0,id=hostdev0,bus=pci.1,addr=0x0:
warning: SMMUv3 does not support notification on MAP: device vfio-pci
will not function properly".

However this is just a warning and this should not prevent the
guest from booting in a reasonable amount of time. This does not
happen currently.

This is due to the fact the VFIO vfio_listener_region_add() calls
memory_region_iommu_replay(). As the SMMUv3 IOMMUMemoryRegionClass
currently does not implement the replay() callback, the default
memory_region_iommu_replay() implementation is used. This latter
loops on the whole notifier's range (48b address space), translates
each page and call the notifier on the resulting entry. This totally
freezes the guest.

The Intel IOMMU implements the replay() function which only
notifies valid page table entries.

In the looming SMMUv3 nested stage VFIO integration, there will be
no need to replay() anything as there will not be any shadow page
tables: the stage 1 page tables are owned by the guest.

So let's implement a void replay() which satisfies both cases.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/arm/smmuv3.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
index e2f07d2864..1f578365ef 100644
--- a/hw/arm/smmuv3.c
+++ b/hw/arm/smmuv3.c
@@ -1489,6 +1489,11 @@ static void smmuv3_notify_flag_changed(IOMMUMemoryRegion *iommu,
     }
 }
 
+static inline void
+smmuv3_replay(IOMMUMemoryRegion *iommu_mr, IOMMUNotifier *n)
+{
+}
+
 static void smmuv3_iommu_memory_region_class_init(ObjectClass *klass,
                                                   void *data)
 {
@@ -1496,6 +1501,7 @@ static void smmuv3_iommu_memory_region_class_init(ObjectClass *klass,
 
     imrc->translate = smmuv3_translate;
     imrc->notify_flag_changed = smmuv3_notify_flag_changed;
+    imrc->replay = smmuv3_replay;
 }
 
 static const TypeInfo smmuv3_type_info = {
-- 
2.20.1