On Wed, Jun 18, 2025 at 11:57 PM Laurent Vivier <lviv...@redhat.com> wrote:
>
> Previously, the vhost_net_get_feature_bits() function in
> hw/net/vhost_net.c used a large switch statement to determine
> the appropriate feature bits based on the NetClientDriver type.
>
> This created unnecessary coupling between the generic vhost layer
> and specific network backends (like TAP, vhost-user, and
> vhost-vdpa).
>
> This patch moves the definition of vhost feature bits directly into the
> NetClientInfo structure for each relevant network client.
>
> This refactoring centralizes feature bit definitions where they're
> needed, making code easier to add new vhost-enabled network backends
> in the future without modifying core vhost logic.
>
> Signed-off-by: Laurent Vivier <lviv...@redhat.com>
> ---
> hw/net/vhost_net.c | 80 ++--------------------------------------
> include/net/net.h | 1 +
> include/net/vhost-vdpa.h | 2 -
> net/tap.c | 19 ++++++++++
> net/vhost-user.c | 43 +++++++++++++++++++++
> net/vhost-vdpa.c | 4 +-
> 6 files changed, 70 insertions(+), 79 deletions(-)
>
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 16dadd022e75..3dff819d2dbd 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -36,86 +36,14 @@
> #include "hw/virtio/virtio-bus.h"
> #include "linux-headers/linux/vhost.h"
>
> -
> -/* Features supported by host kernel. */
> -static const int kernel_feature_bits[] = {
> - VIRTIO_F_NOTIFY_ON_EMPTY,
> - VIRTIO_RING_F_INDIRECT_DESC,
> - VIRTIO_RING_F_EVENT_IDX,
> - VIRTIO_NET_F_MRG_RXBUF,
> - VIRTIO_F_VERSION_1,
> - VIRTIO_NET_F_MTU,
> - VIRTIO_F_IOMMU_PLATFORM,
> - VIRTIO_F_RING_PACKED,
> - VIRTIO_F_RING_RESET,
> - VIRTIO_F_IN_ORDER,
> - VIRTIO_F_NOTIFICATION_DATA,
> - VIRTIO_NET_F_RSC_EXT,
> - VIRTIO_NET_F_HASH_REPORT,
> - VHOST_INVALID_FEATURE_BIT
> -};
> -
> -/* Features supported by others. */
> -static const int user_feature_bits[] = {
> - VIRTIO_F_NOTIFY_ON_EMPTY,
> - VIRTIO_F_NOTIFICATION_DATA,
> - VIRTIO_RING_F_INDIRECT_DESC,
> - VIRTIO_RING_F_EVENT_IDX,
> -
> - VIRTIO_F_ANY_LAYOUT,
> - VIRTIO_F_VERSION_1,
> - VIRTIO_NET_F_CSUM,
> - VIRTIO_NET_F_GUEST_CSUM,
> - VIRTIO_NET_F_GSO,
> - VIRTIO_NET_F_GUEST_TSO4,
> - VIRTIO_NET_F_GUEST_TSO6,
> - VIRTIO_NET_F_GUEST_ECN,
> - VIRTIO_NET_F_GUEST_UFO,
> - VIRTIO_NET_F_HOST_TSO4,
> - VIRTIO_NET_F_HOST_TSO6,
> - VIRTIO_NET_F_HOST_ECN,
> - VIRTIO_NET_F_HOST_UFO,
> - VIRTIO_NET_F_MRG_RXBUF,
> - VIRTIO_NET_F_MTU,
> - VIRTIO_F_IOMMU_PLATFORM,
> - VIRTIO_F_RING_PACKED,
> - VIRTIO_F_RING_RESET,
> - VIRTIO_F_IN_ORDER,
> - VIRTIO_NET_F_RSS,
> - VIRTIO_NET_F_RSC_EXT,
> - VIRTIO_NET_F_HASH_REPORT,
> - VIRTIO_NET_F_GUEST_USO4,
> - VIRTIO_NET_F_GUEST_USO6,
> - VIRTIO_NET_F_HOST_USO,
> -
> - /* This bit implies RARP isn't sent by QEMU out of band */
> - VIRTIO_NET_F_GUEST_ANNOUNCE,
> -
> - VIRTIO_NET_F_MQ,
> -
> - VHOST_INVALID_FEATURE_BIT
> -};
> -
> static const int *vhost_net_get_feature_bits(struct vhost_net *net)
> {
> - if (net->nc->info->type == NET_CLIENT_DRIVER_TAP) {
> - return kernel_feature_bits;
> - }
> -
> - if (qemu_is_vhost_user(net->nc)) {
> - return user_feature_bits;
> + if (net->nc->info->vhost_feature_bits == NULL) {
> + error_report("Feature bits not defined for this type: %d",
> + net->nc->info->type);
> }
>
> -#ifdef CONFIG_VHOST_NET_VDPA
> - if (net->nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA) {
> - return vdpa_feature_bits;
> - }
> -#endif
> -
> - error_report("Feature bits not defined for this type: %d",
> - net->nc->info->type);
> -
> - return 0;
> + return net->nc->info->vhost_feature_bits;
> }
>
> uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
> diff --git a/include/net/net.h b/include/net/net.h
> index 8a62cd6e8aab..dd11be11a39f 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -94,6 +94,7 @@ typedef struct NetClientInfo {
> NetAnnounce *announce;
> SetSteeringEBPF *set_steering_ebpf;
> NetCheckPeerType *check_peer_type;
> + const int *vhost_feature_bits;
> IsVHostUser *is_vhost_user;
> GetVHostNet *get_vhost_net;
Assuming we had already had get_vhost_net, it looks to me it's better
to move/reuse the vhost_feature_bits there?
Thanks
