[RFC PATCH v2 3/4] vhost: register and change IOMMU flag depending on Device-TLB state

[Viktor Prutyanov <viktor@daynix.com>]

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

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2001312
Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
---
 hw/virtio/vhost-backend.c         |  6 ++++++
 hw/virtio/vhost.c                 | 26 ++++++++++++++++++++++++--
 include/hw/virtio/vhost-backend.h |  4 ++++
 include/hw/virtio/vhost.h         |  1 +
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 8e581575c9..30eb71fb83 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -297,6 +297,11 @@ static void vhost_kernel_set_iotlb_callback(struct vhost_dev *dev,
         qemu_set_fd_handler((uintptr_t)dev->opaque, NULL, NULL, NULL);
 }
 
+static void vhost_kernel_toggle_device_iotlb(struct vhost_dev *dev, int enable)
+{
+    vhost_toggle_device_iotlb(dev, enable);
+}
+
 const VhostOps kernel_ops = {
         .backend_type = VHOST_BACKEND_TYPE_KERNEL,
         .vhost_backend_init = vhost_kernel_init,
@@ -328,6 +333,7 @@ const VhostOps kernel_ops = {
         .vhost_vsock_set_running = vhost_kernel_vsock_set_running,
         .vhost_set_iotlb_callback = vhost_kernel_set_iotlb_callback,
         .vhost_send_device_iotlb_msg = vhost_kernel_send_device_iotlb_msg,
+        .vhost_toggle_device_iotlb = vhost_kernel_toggle_device_iotlb,
 };
 #endif
 
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index a266396576..1bfcc6d263 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->device_iotlb_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->device_iotlb_enabled ? NULL : &error_fatal);
     if (ret) {
         /*
          * Some vIOMMUs do not support dev-iotlb yet.  If so, try to use the
@@ -841,6 +844,25 @@ static void vhost_iommu_region_del(MemoryListener *listener,
     }
 }
 
+void vhost_toggle_device_iotlb(struct vhost_dev *dev, bool enable)
+{
+    struct vhost_iommu *iommu;
+    int ret;
+
+    QLIST_FOREACH(iommu, &dev->iommu_list, iommu_next) {
+        memory_region_unregister_iommu_notifier(iommu->mr, &iommu->n);
+        iommu->n.notifier_flags = enable ?
+                IOMMU_NOTIFIER_DEVIOTLB_UNMAP : IOMMU_NOTIFIER_UNMAP;
+        ret = memory_region_register_iommu_notifier(iommu->mr, &iommu->n,
+                enable ? NULL : &error_fatal);
+        if (ret) {
+            iommu->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
+            memory_region_register_iommu_notifier(iommu->mr, &iommu->n,
+                                                  &error_fatal);
+        }
+    }
+}
+
 static int vhost_virtqueue_set_addr(struct vhost_dev *dev,
                                     struct vhost_virtqueue *vq,
                                     unsigned idx, bool enable_log)
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index ec3fbae58d..f8e9660a96 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -133,6 +133,9 @@ typedef int (*vhost_set_config_call_op)(struct vhost_dev *dev,
 
 typedef void (*vhost_reset_status_op)(struct vhost_dev *dev);
 
+typedef void (*vhost_toggle_device_iotlb_op)(struct vhost_dev *dev,
+                                             int enabled);
+
 typedef struct VhostOps {
     VhostBackendType backend_type;
     vhost_backend_init vhost_backend_init;
@@ -181,6 +184,7 @@ typedef struct VhostOps {
     vhost_force_iommu_op vhost_force_iommu;
     vhost_set_config_call_op vhost_set_config_call;
     vhost_reset_status_op vhost_reset_status;
+    vhost_toggle_device_iotlb_op vhost_toggle_device_iotlb;
 } VhostOps;
 
 int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index a52f273347..b3f585c6cd 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -320,6 +320,7 @@ bool vhost_has_free_slot(void);
 int vhost_net_set_backend(struct vhost_dev *hdev,
                           struct vhost_vring_file *file);
 
+void vhost_toggle_device_iotlb(struct vhost_dev *dev, bool enable);
 int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
 
 int vhost_virtqueue_start(struct vhost_dev *dev, struct VirtIODevice *vdev,
-- 
2.35.1