Virtualization - Dec 2021 - [PATCH v2 03/10] vdpa: Read device configuration only if FEATURES_OK

On Mon, Dec 13, 2021 at 10:43 PM Eli Cohen <elic at nvidia.com>
wrote:
>
> Avoid reading device configuration during feature negotiation. Read
> device status and verify that VIRTIO_CONFIG_S_FEATURES_OK is set.
> Otherwise, return -EAGAIN.
>
> Signed-off-by: Eli Cohen <elic at nvidia.com>

> ---
>  drivers/vdpa/vdpa.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 42d71d60d5dc..5749cf0a1500 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -819,8 +819,15 @@ vdpa_dev_config_fill(struct vdpa_device *vdev, struct
sk_buff *msg, u32 portid,
>  {
>         u32 device_id;
>         void *hdr;
> +       u8 status;
>         int err;
>
> +       status = vdev->config->get_status(vdev);
> +       if (!(status & VIRTIO_CONFIG_S_FEATURES_OK)) {
> +               NL_SET_ERR_MSG_MOD(extack, "Features negotiation not
completed");
> +               return -EAGAIN;
> +       }
> +
>         hdr = genlmsg_put(msg, portid, seq, &vdpa_nl_family, flags,
>                           VDPA_CMD_DEV_CONFIG_GET);
>         if (!hdr)
It looks to me we need to synchronize this with set_status() and
cf_mutex (set_config).

Or simply return all the config space (the maximum set of features)

Thanks
> --
> 2.33.1
>