Re: [PATCH v4 1/2] vhost: register and change IOMMU flag depending on Device-TLB state

[Jason Wang]

On Thu, May 25, 2023 at 8:58 PM Viktor Prutyanov <viktor@daynix.com> wrote:
>
> 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>

Acked-by: Jason Wang <jasowang@redhat.com>

Thanks

> ---
>  hw/virtio/vhost.c         | 38 ++++++++++++++++++++++++++------------
>  include/hw/virtio/vhost.h |  1 +
>  2 files changed, 27 insertions(+), 12 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 23da579ce2..e48507b5a1 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -781,7 +781,6 @@ static void vhost_iommu_region_add(MemoryListener 
> *listener,
>      Int128 end;
>      int iommu_idx;
>      IOMMUMemoryRegion *iommu_mr;
> -    int ret;
>
>      if (!memory_region_is_iommu(section->mr)) {
>          return;
> @@ -796,7 +795,9 @@ 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);
> @@ -804,16 +805,8 @@ 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);
> -    if (ret) {
> -        /*
> -         * Some vIOMMUs do not support dev-iotlb yet.  If so, try to use the
> -         * UNMAP legacy message
> -         */
> -        iommu->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
> -        memory_region_register_iommu_notifier(section->mr, &iommu->n,
> -                                              &error_fatal);
> -    }
> +    memory_region_register_iommu_notifier(section->mr, &iommu->n,
> +                                          &error_fatal);
>      QLIST_INSERT_HEAD(&dev->iommu_list, iommu, iommu_next);
>      /* TODO: can replay help performance here? */
>  }
> @@ -841,6 +834,27 @@ static void vhost_iommu_region_del(MemoryListener 
> *listener,
>      }
>  }
>
> +void vhost_toggle_device_iotlb(VirtIODevice *vdev)
> +{
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
> +    struct vhost_dev *dev;
> +    struct vhost_iommu *iommu;
> +
> +    if (vdev->vhost_started) {
> +        dev = vdc->get_vhost(vdev);
> +    } else {
> +        return;
> +    }
> +
> +    QLIST_FOREACH(iommu, &dev->iommu_list, iommu_next) {
> +        memory_region_unregister_iommu_notifier(iommu->mr, &iommu->n);
> +        iommu->n.notifier_flags = vdev->device_iotlb_enabled ?
> +                IOMMU_NOTIFIER_DEVIOTLB_UNMAP : 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.h b/include/hw/virtio/vhost.h
> index f7f10c8fb7..6a173cb9fa 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(VirtIODevice *vdev);
>  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,
> --
> 2.21.0
>