Re: [RFC PATCH v1] vhost-vsock: SOCK_SEQPACKET feature bit support

[Stefano Garzarella]

On Mon, Jun 21, 2021 at 05:07:41PM +0300, Arseny Krasnov wrote:
> This adds processing of VIRTIO_VSOCK_F_SEQPACKET features bit. Guest
> negotiates it with vhost, thus both will know that SOCK_SEQPACKET
> supported by peer.
>
> Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
> ---
> hw/virtio/vhost-vsock.c                       | 16 +++++++++++++++-
> include/standard-headers/linux/virtio_vsock.h |  3 +++
> 2 files changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> index 8ddfb9abfe..fc8c143df9 100644
> --- a/hw/virtio/vhost-vsock.c
> +++ b/hw/virtio/vhost-vsock.c
> @@ -108,10 +108,23 @@ static uint64_t vhost_vsock_get_features(VirtIODevice 
> *vdev,
>                                          uint64_t requested_features,
>                                          Error **errp)
> {
> -    /* No feature bits used yet */
> +    VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
> +
> +    if (virtio_has_feature(vvc->vhost_dev.features, VIRTIO_VSOCK_F_SEQPACKET)) 
> {
> +        virtio_add_feature(&requested_features, VIRTIO_VSOCK_F_SEQPACKET);
> +    }
> +

I think we can use vhost_get_features(), take a look at 
hw/virtio/vhost-user-vsock.c


>     return requested_features;
> }
>
> +static void vhost_vsock_set_features(VirtIODevice *vdev, uint64_t features)
> +{
> +    VHostVSockCommon *vvc = VHOST_VSOCK_COMMON(vdev);
> +    const VhostOps *vhost_ops = vvc->vhost_dev.vhost_ops;
> +
> +    vhost_ops->vhost_set_features(&vvc->vhost_dev, features);

Maybe we can avoid vhost_vsock_set_features(), because in 
vhost_vsock_common_start() we have this code that should do the same, 
sice vhost_dev_start() already call vhost_set_features() with the acked 
features:

    vvc->vhost_dev.acked_features = vdev->guest_features;
    ret = vhost_dev_start(&vvc->vhost_dev, vdev);

I'm not sure if it works. Can you try simply removing 
vhost_vsock_set_features()?

Thanks,
Stefano

> +}
> +
> static const VMStateDescription vmstate_virtio_vhost_vsock = {
>     .name = "virtio-vhost_vsock",
>     .minimum_version_id = VHOST_VSOCK_SAVEVM_VERSION,
> @@ -224,6 +237,7 @@ static void vhost_vsock_class_init(ObjectClass *klass, void 
> *data)
>     vdc->realize = vhost_vsock_device_realize;
>     vdc->unrealize = vhost_vsock_device_unrealize;
>     vdc->get_features = vhost_vsock_get_features;
> +    vdc->set_features = vhost_vsock_set_features;
>     vdc->get_config = vhost_vsock_get_config;
>     vdc->set_status = vhost_vsock_set_status;
> }
> diff --git a/include/standard-headers/linux/virtio_vsock.h 
> b/include/standard-headers/linux/virtio_vsock.h
> index be443211ce..5eac522ee2 100644
> --- a/include/standard-headers/linux/virtio_vsock.h
> +++ b/include/standard-headers/linux/virtio_vsock.h
> @@ -38,6 +38,9 @@
> #include "standard-headers/linux/virtio_ids.h"
> #include "standard-headers/linux/virtio_config.h"
>
> +/* The feature bitmap for virtio vsock */
> +#define VIRTIO_VSOCK_F_SEQPACKET       1       /* SOCK_SEQPACKET 
> supported */
> +
> struct virtio_vsock_config {
>         uint64_t guest_cid;
> } QEMU_PACKED;
> --
> 2.25.1