When we have guest visible IOMMUs, we allow notifiers to be registered
which will be informed of all changes to IOMMU mappings. This is used by
vfio to keep the host IOMMU mappings in sync with guest IOMMU mappings.
However, unlike with a memory region listener, an iommu notifier won't be
told about any mappings which already exist in the (guest) IOMMU at the
time it is registered. This can cause problems if hotplugging a VFIO
device onto a guest bus which had existing guest IOMMU mappings, but didn't
previously have an VFIO devices (and hence no host IOMMU mappings).
This adds a memory_region_register_iommu_notifier_replay() function to
handle this case. As well as registering the new notifier it replays
existing mappings. Because the IOMMU memory region doesn't internally
remember the granularity of the guest IOMMU it has a small hack where the
caller must specify a granularity at which to replay mappings.
If there are finer mappings in the guest IOMMU these will be reported in
the iotlb structures passed to the notifier which it must handle (probably
causing it to flag an error). This isn't new - the VFIO iommu notifier
must already handle notifications about guest IOMMU mappings too short
for it to represent in the host IOMMU.
Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
---
include/exec/memory.h | 16 ++++++++++++++++
memory.c | 18 ++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 5baaf48..3cf145b 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -583,6 +583,22 @@ void memory_region_notify_iommu(MemoryRegion *mr,
void memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n);
/**
+ * memory_region_register_iommu_notifier_replay: register a notifier
+ * for changes to IOMMU translation entries, and replay existing IOMMU
+ * translations to the new notifier.
+ *
+ * @mr: the memory region to observe
+ * @n: the notifier to be added; the notifier receives a pointer to an
+ * #IOMMUTLBEntry as the opaque value; the pointer ceases to be
+ * valid on exit from the notifier.
+ * @granularity: Minimum page granularity to replay notifications for
+ * @is_write: Whether to treat the replay as a translate "write"
+ * through the iommu
+ */
+void memory_region_register_iommu_notifier_replay(MemoryRegion *mr, Notifier
*n,
+ hwaddr granularity, bool
is_write);
+
+/**
* memory_region_unregister_iommu_notifier: unregister a notifier for
* changes to IOMMU translation entries.
*
diff --git a/memory.c b/memory.c
index 0d8b2d9..6b5a2f1 100644
--- a/memory.c
+++ b/memory.c
@@ -1403,6 +1403,24 @@ void memory_region_register_iommu_notifier(MemoryRegion
*mr, Notifier *n)
notifier_list_add(&mr->iommu_notify, n);
}
+void memory_region_register_iommu_notifier_replay(MemoryRegion *mr, Notifier
*n,
+ hwaddr granularity, bool
is_write)
+{
+ hwaddr addr;
+ IOMMUTLBEntry iotlb;
+
+ memory_region_register_iommu_notifier(mr, n);
+
+ for (addr = 0;
+ int128_lt(int128_make64(addr), mr->size);
+ addr += granularity) {
+
+ iotlb = mr->iommu_ops->translate(mr, addr, is_write);
+ if (iotlb.perm != IOMMU_NONE)
+ n->notify(n, &iotlb);
+ }
+}
+
void memory_region_unregister_iommu_notifier(Notifier *n)
{
notifier_remove(n);
--
2.4.3
