[Qemu-devel] [RFC PATCH qemu] spapr_iommu, vfio, memory: Notify IOMMU about starting/stopping listening

[Alexey Kardashevskiy <aik@ozlabs.ru>]

The sPAPR TCE tables manage 2 copies when VFIO is using an IOMMU -
a guest view of the table and a hardware TCE table. If there is no VFIO
presense in the address space, then just the guest view is used, if
this is the case, it is allocated in the KVM. However since there is no
support yet for VFIO in KVM TCE hypercalls, when we start using VFIO,
we need to move the guest view from KVM to the userspace; and we need
to do this for every IOMMU on a bus with VFIO devices.

This adds notify_started/notify_stopped callbacks in MemoryRegionIOMMUOps
to notify IOMMU that listeners were set/removed. This allows IOMMU to
take necessary steps before actual notifications happen and do proper
cleanup when the last notifier is removed.

This implements the callbacks for the sPAPR IOMMU - notify_started()
reallocated the guest view to the user space, notify_stopped() does
the opposite.

This removes explicit spapr_tce_set_need_vfio() call from PCI hotplug
path as the new callbacks do this better - they notify IOMMU at
the exact moment when the configuration is changed, and this also
includes the case of PCI hot unplug.

This adds MemoryRegion* to memory_region_unregister_iommu_notifier()
as we need iommu_ops to call notify_stopped() and Notifier* does not
store the owner.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---


Is this any better? If so, I'll repost as a part of "v17". Thanks.



---
Changes:
v17:
* replaced IOMMU users counting with simple QLIST_EMPTY()
* renamed the callbacks
* removed requirement for region_del() to be called on memory_listener_unregister()

v16:
* added a use counter in VFIOAddressSpace->VFIOIOMMUMR

v15:
* s/need_vfio/vfio-Users/g
---
 hw/ppc/spapr_iommu.c  | 12 ++++++++++++
 hw/ppc/spapr_pci.c    |  6 ------
 hw/vfio/common.c      |  5 +++--
 include/exec/memory.h |  8 +++++++-
 memory.c              | 10 +++++++++-
 5 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/hw/ppc/spapr_iommu.c b/hw/ppc/spapr_iommu.c
index 73bc26b..fd38006 100644
--- a/hw/ppc/spapr_iommu.c
+++ b/hw/ppc/spapr_iommu.c
@@ -156,6 +156,16 @@ static uint64_t spapr_tce_get_page_sizes(MemoryRegion *iommu)
     return 1ULL << tcet->page_shift;
 }
 
+static void spapr_tce_notify_started(MemoryRegion *iommu)
+{
+    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), true);
+}
+
+static void spapr_tce_notify_stopped(MemoryRegion *iommu)
+{
+    spapr_tce_set_need_vfio(container_of(iommu, sPAPRTCETable, iommu), false);
+}
+
 static void spapr_tce_table_do_enable(sPAPRTCETable *tcet);
 static void spapr_tce_table_do_disable(sPAPRTCETable *tcet);
 
@@ -240,6 +250,8 @@ static const VMStateDescription vmstate_spapr_tce_table = {
 static MemoryRegionIOMMUOps spapr_iommu_ops = {
     .translate = spapr_tce_translate_iommu,
     .get_page_sizes = spapr_tce_get_page_sizes,
+    .notify_started = spapr_tce_notify_started,
+    .notify_stopped = spapr_tce_notify_stopped,
 };
 
 static int spapr_tce_table_realize(DeviceState *dev)
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 68e77b0..7c2c622 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1089,12 +1089,6 @@ static void spapr_phb_add_pci_device(sPAPRDRConnector *drc,
     void *fdt = NULL;
     int fdt_start_offset = 0, fdt_size;
 
-    if (object_dynamic_cast(OBJECT(pdev), "vfio-pci")) {
-        sPAPRTCETable *tcet = spapr_tce_find_by_liobn(phb->dma_liobn);
-
-        spapr_tce_set_need_vfio(tcet, true);
-    }
-
     if (dev->hotplugged) {
         fdt = create_device_tree(&fdt_size);
         fdt_start_offset = spapr_create_pci_child_dt(phb, pdev, fdt, 0);
diff --git a/hw/vfio/common.c b/hw/vfio/common.c
index 2e4f703..d1fa9ab 100644
--- a/hw/vfio/common.c
+++ b/hw/vfio/common.c
@@ -523,7 +523,8 @@ 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->n);
+                memory_region_unregister_iommu_notifier(giommu->iommu,
+                                                        &giommu->n);
                 QLIST_REMOVE(giommu, giommu_next);
                 g_free(giommu);
                 break;
@@ -1040,7 +1041,7 @@ static void vfio_disconnect_container(VFIOGroup *group)
         QLIST_REMOVE(container, next);
 
         QLIST_FOREACH_SAFE(giommu, &container->giommu_list, giommu_next, tmp) {
-            memory_region_unregister_iommu_notifier(&giommu->n);
+            memory_region_unregister_iommu_notifier(giommu->iommu, &giommu->n);
             QLIST_REMOVE(giommu, giommu_next);
             g_free(giommu);
         }
diff --git a/include/exec/memory.h b/include/exec/memory.h
index bfb08d4..1c41eb6 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -151,6 +151,10 @@ struct MemoryRegionIOMMUOps {
     IOMMUTLBEntry (*translate)(MemoryRegion *iommu, hwaddr addr, bool is_write);
     /* Returns supported page sizes */
     uint64_t (*get_page_sizes)(MemoryRegion *iommu);
+    /* Called when the first notifier is set */
+    void (*notify_started)(MemoryRegion *iommu);
+    /* Called when the last notifier is removed */
+    void (*notify_stopped)(MemoryRegion *iommu);
 };
 
 typedef struct CoalescedMemoryRange CoalescedMemoryRange;
@@ -620,9 +624,11 @@ void memory_region_iommu_replay(MemoryRegion *mr, Notifier *n, bool is_write);
  * memory_region_unregister_iommu_notifier: unregister a notifier for
  * changes to IOMMU translation entries.
  *
+ * @mr: the memory region which was observed and for which notity_stopped()
+ *      needs to be called
  * @n: the notifier to be removed.
  */
-void memory_region_unregister_iommu_notifier(Notifier *n);
+void memory_region_unregister_iommu_notifier(MemoryRegion *mr, Notifier *n);
 
 /**
  * memory_region_name: get a memory region's name
diff --git a/memory.c b/memory.c
index d22cf5e..fcf978a 100644
--- a/memory.c
+++ b/memory.c
@@ -1512,6 +1512,10 @@ bool memory_region_is_logging(MemoryRegion *mr, uint8_t client)
 
 void memory_region_register_iommu_notifier(MemoryRegion *mr, Notifier *n)
 {
+    if (mr->iommu_ops->notify_started &&
+        QLIST_EMPTY(&mr->iommu_notify.notifiers)) {
+        mr->iommu_ops->notify_started(mr);
+    }
     notifier_list_add(&mr->iommu_notify, n);
 }
 
@@ -1545,9 +1549,13 @@ void memory_region_iommu_replay(MemoryRegion *mr, Notifier *n, bool is_write)
     }
 }
 
-void memory_region_unregister_iommu_notifier(Notifier *n)
+void memory_region_unregister_iommu_notifier(MemoryRegion *mr, Notifier *n)
 {
     notifier_remove(n);
+    if (mr->iommu_ops->notify_stopped &&
+        QLIST_EMPTY(&mr->iommu_notify.notifiers)) {
+        mr->iommu_ops->notify_stopped(mr);
+    }
 }
 
 void memory_region_notify_iommu(MemoryRegion *mr,
-- 
2.5.0.rc3