On Fri, Jul 18, 2025 at 4:53 PM Paolo Abeni <pab...@redhat.com> wrote:
>
> Similar to virtio infra, vhost core maintains the features status
> in the full extended format and allows the devices to implement
> extended version of the getter/setter.
>
> Note that 'protocol_features' are not extended: they are only
> used by vhost-user, and the latter device is not going to implement
> extended features soon.
>
> Signed-off-by: Paolo Abeni <pab...@redhat.com>
> ---
> v2 -> v3:
> - fix compile warning
> - _array -> _ex
>
> v1 -> v2:
> - uint128_t -> uint64_t[]
> - add _ex() variant of features manipulation helpers
> ---
> hw/virtio/vhost.c | 73 +++++++++++++++++++++++++++----
> include/hw/virtio/vhost-backend.h | 6 +++
> include/hw/virtio/vhost.h | 33 ++++++++++++--
> 3 files changed, 100 insertions(+), 12 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index c30ea1156e..85ae1e4d4c 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -972,20 +972,34 @@ static int vhost_virtqueue_set_addr(struct vhost_dev
> *dev,
> static int vhost_dev_set_features(struct vhost_dev *dev,
> bool enable_log)
> {
> - uint64_t features = dev->acked_features;
> + uint64_t features[VIRTIO_FEATURES_DWORDS];
> int r;
> +
> + virtio_features_copy(features, dev->acked_features_ex);
> if (enable_log) {
> - features |= 0x1ULL << VHOST_F_LOG_ALL;
> + virtio_add_feature_ex(features, VHOST_F_LOG_ALL);
> }
> if (!vhost_dev_has_iommu(dev)) {
> - features &= ~(0x1ULL << VIRTIO_F_IOMMU_PLATFORM);
> + virtio_clear_feature_ex(features, VIRTIO_F_IOMMU_PLATFORM);
> }
> if (dev->vhost_ops->vhost_force_iommu) {
> if (dev->vhost_ops->vhost_force_iommu(dev) == true) {
> - features |= 0x1ULL << VIRTIO_F_IOMMU_PLATFORM;
> + virtio_add_feature_ex(features, VIRTIO_F_IOMMU_PLATFORM);
> }
> }
> - r = dev->vhost_ops->vhost_set_features(dev, features);
> +
> + if (virtio_features_use_extended(features) &&
> + !dev->vhost_ops->vhost_set_features_ex) {
> + VHOST_OPS_DEBUG(r, "extended features without device support");
> + r = -EINVAL;
> + goto out;
> + }
> +
> + if (dev->vhost_ops->vhost_set_features_ex) {
> + r = dev->vhost_ops->vhost_set_features_ex(dev, features);
> + } else {
> + r = dev->vhost_ops->vhost_set_features(dev, features[0]);
> + }
> if (r < 0) {
> VHOST_OPS_DEBUG(r, "vhost_set_features failed");
> goto out;
> @@ -1506,12 +1520,27 @@ static void vhost_virtqueue_cleanup(struct
> vhost_virtqueue *vq)
> }
> }
>
> +static int vhost_dev_get_features(struct vhost_dev *hdev,
> + uint64_t *features)
> +{
> + uint64_t features64;
> + int r;
> +
> + if (hdev->vhost_ops->vhost_get_features_ex) {
> + return hdev->vhost_ops->vhost_get_features_ex(hdev, features);
> + }
> +
> + r = hdev->vhost_ops->vhost_get_features(hdev, &features64);
> + virtio_features_from_u64(features, features64);
> + return r;
> +}
Nit: let's have a vhost_dev_set_features() as well?
Thanks
