[RFC PATCH 4/4] vhost: register and change IOMMU flag depending on ATS state

[Viktor Prutyanov]

The guest can disable or never enable ATS. In these cases, Device-TLB
can't be used even if enabled in QEMU. So, check ATS state before
registering IOMMU notifier and select flag depending on that. Also,
change IOMMU notifier flag if ATS state is changed.

Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
---
 hw/virtio/vhost.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index eb8c4c378c..1b14937020 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -796,7 +796,9 @@ static void vhost_iommu_region_add(MemoryListener *listener,
     iommu_idx = memory_region_iommu_attrs_to_index(iommu_mr,
                                                    MEMTXATTRS_UNSPECIFIED);
     iommu_notifier_init(&iommu->n, vhost_iommu_unmap_notify,
-                        IOMMU_NOTIFIER_DEVIOTLB_UNMAP,
+                        dev->vdev->ats_enabled ?
+                            IOMMU_NOTIFIER_DEVIOTLB_UNMAP :
+                            IOMMU_NOTIFIER_UNMAP,
                         section->offset_within_region,
                         int128_get64(end),
                         iommu_idx);
@@ -804,7 +806,8 @@ static void vhost_iommu_region_add(MemoryListener *listener,
     iommu->iommu_offset = section->offset_within_address_space -
                           section->offset_within_region;
     iommu->hdev = dev;
-    ret = memory_region_register_iommu_notifier(section->mr, &iommu->n, NULL);
+    ret = memory_region_register_iommu_notifier(section->mr, &iommu->n,
+            dev->vdev->ats_enabled ? NULL : &error_fatal);
     if (ret) {
         /*
          * Some vIOMMUs do not support dev-iotlb yet.  If so, try to use the
@@ -818,6 +821,19 @@ static void vhost_iommu_region_add(MemoryListener 
*listener,
     /* TODO: can replay help performance here? */
 }
 
+static void vhost_deviotlb_ctrl_trigger(bool enable, struct VirtIODevice *vdev)
+{
+    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+    struct vhost_dev *hdev = vdc->get_vhost(vdev);
+    struct vhost_iommu *iommu;
+
+    QLIST_FOREACH(iommu, &hdev->iommu_list, iommu_next) {
+        iommu->n.notifier_flags = enable ?
+            IOMMU_NOTIFIER_DEVIOTLB_UNMAP : IOMMU_NOTIFIER_UNMAP;
+        memory_region_iommu_notify_flags_changed(iommu->mr);
+    }
+}
+
 static void vhost_iommu_region_del(MemoryListener *listener,
                                    MemoryRegionSection *section)
 {
@@ -2000,6 +2016,8 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice 
*vdev, bool vrings)
             struct vhost_virtqueue *vq = hdev->vqs + i;
             vhost_device_iotlb_miss(hdev, vq->used_phys, true);
         }
+
+        vdev->ats_ctrl_trigger = vhost_deviotlb_ctrl_trigger;
     }
     vhost_start_config_intr(hdev);
     return 0;
@@ -2055,6 +2073,7 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice 
*vdev, bool vrings)
             hdev->vhost_ops->vhost_set_iotlb_callback(hdev, false);
         }
         memory_listener_unregister(&hdev->iommu_listener);
+        vdev->ats_ctrl_trigger = NULL;
     }
     vhost_stop_config_intr(hdev);
     vhost_log_put(hdev, true);
-- 
2.21.0