When one IOMMU memory region is splitted into multiple memory sections,
vfio will register multiple same notifiers to a vIOMMU for the same
region. That's not sensible. What we need is to register one IOMMU
notifier for each IOMMU region, not per section.
Solution is simple - we traverse the container->giommu_list, and skip
the registration if memory region is already registered. Instead, we use
a refcount to note down how many sections are referencing the
VFIOGuestIOMMU.
To make vfio's region_add() short, vfio_listener_region_add_iommu() is
introduced.
Signed-off-by: Peter Xu <pet...@redhat.com>
---
v2:
- use refcount to make sure the VFIOGuestIOMMU won't be freed until the
last referencing memory region section is deleted [David]
(David suggested another way to implement - to store section range
info in IOMMUNotifier. Will post another patch for it, and we can
choose either one we want)
Signed-off-by: Peter Xu <pet...@redhat.com>
---
hw/vfio/common.c | 71 ++++++++++++++++++++++++++++---------------
include/hw/vfio/vfio-common.h | 1 +
2 files changed, 47 insertions(+), 25 deletions(-)
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 801578b..e75e25c 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -360,6 +360,41 @@ out:
rcu_read_unlock();
}
+static void vfio_listener_region_add_iommu(VFIOContainer *container,
+ MemoryRegionSection *section,
+ hwaddr iova,
+ hwaddr end)
+{
+ VFIOGuestIOMMU *giommu;
+
+ QLIST_FOREACH(giommu, &container->giommu_list, giommu_next) {
+ if (giommu->iommu == section->mr) {
+ atomic_inc(&giommu->refcount);
+ return;
+ }
+ }
+
+ trace_vfio_listener_region_add_iommu(iova, end);
+
+ /*
+ * FIXME: For VFIO iommu types which have KVM acceleration to
+ * avoid bouncing all map/unmaps through qemu this way, this
+ * would be the right place to wire that up (tell the KVM
+ * device emulation the VFIO iommu handles to use).
+ */
+ giommu = g_malloc0(sizeof(*giommu));
+ giommu->iommu = section->mr;
+ giommu->iommu_offset = section->offset_within_address_space -
+ section->offset_within_region;
+ giommu->container = container;
+ giommu->n.notify = vfio_iommu_map_notify;
+ giommu->n.notifier_flags = IOMMU_NOTIFIER_ALL;
+ atomic_set(&giommu->refcount, 1);
+ QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next);
+ memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
+ memory_region_iommu_replay(giommu->iommu, &giommu->n, false);
+}
+
static void vfio_listener_region_add(MemoryListener *listener,
MemoryRegionSection *section)
{
@@ -439,27 +474,7 @@ static void vfio_listener_region_add(MemoryListener
*listener,
memory_region_ref(section->mr);
if (memory_region_is_iommu(section->mr)) {
- VFIOGuestIOMMU *giommu;
-
- trace_vfio_listener_region_add_iommu(iova, end);
- /*
- * FIXME: For VFIO iommu types which have KVM acceleration to
- * avoid bouncing all map/unmaps through qemu this way, this
- * would be the right place to wire that up (tell the KVM
- * device emulation the VFIO iommu handles to use).
- */
- giommu = g_malloc0(sizeof(*giommu));
- giommu->iommu = section->mr;
- giommu->iommu_offset = section->offset_within_address_space -
- section->offset_within_region;
- giommu->container = container;
- giommu->n.notify = vfio_iommu_map_notify;
- giommu->n.notifier_flags = IOMMU_NOTIFIER_ALL;
- QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next);
-
- memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
- memory_region_iommu_replay(giommu->iommu, &giommu->n, false);
-
+ vfio_listener_region_add_iommu(container, section, iova, end);
return;
}
@@ -526,10 +541,16 @@ static void vfio_listener_region_del(MemoryListener
*listener,
QLIST_FOREACH(giommu, &container->giommu_list, giommu_next) {
if (giommu->iommu == section->mr) {
- memory_region_unregister_iommu_notifier(giommu->iommu,
- &giommu->n);
- QLIST_REMOVE(giommu, giommu_next);
- g_free(giommu);
+ /*
+ * Only release the object when the last referencing
+ * memory region section is deleted
+ */
+ if (atomic_fetch_dec(&giommu->refcount) == 1) {
+ memory_region_unregister_iommu_notifier(giommu->iommu,
+ &giommu->n);
+ QLIST_REMOVE(giommu, giommu_next);
+ g_free(giommu);
+ }
break;
}
}
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index c582de1..8817f8a 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -97,6 +97,7 @@ typedef struct VFIOGuestIOMMU {
MemoryRegion *iommu;
hwaddr iommu_offset;
IOMMUNotifier n;
+ unsigned int refcount;
QLIST_ENTRY(VFIOGuestIOMMU) giommu_next;
} VFIOGuestIOMMU;
--
2.7.4
