Re: [RFC v1 6/6] virtio/vsock: add sysfs for rx buf len for dgram

[Stefano Garzarella <sgarzare@xxxxxxxxxx>]

On Wed, Jun 09, 2021 at 11:24:58PM +0000, Jiang Wang wrote:
> Make rx buf len configurable via sysfs
>
> Signed-off-by: Jiang Wang <jiang.wang@xxxxxxxxxxxxx>
> ---
> net/vmw_vsock/virtio_transport.c | 37 +++++++++++++++++++++++++++++++++++--
> 1 file changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
> index cf47aadb0c34..2e4dd9c48472 100644
> --- a/net/vmw_vsock/virtio_transport.c
> +++ b/net/vmw_vsock/virtio_transport.c
> @@ -29,6 +29,14 @@ static struct virtio_vsock __rcu *the_virtio_vsock;
> static struct virtio_vsock *the_virtio_vsock_dgram;
> static DEFINE_MUTEX(the_virtio_vsock_mutex); /* protects the_virtio_vsock */
>
> +static int rx_buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
> +static struct kobject *kobj_ref;
> +static ssize_t  sysfs_show(struct kobject *kobj,
> +			struct kobj_attribute *attr, char *buf);
> +static ssize_t  sysfs_store(struct kobject *kobj,
> +			struct kobj_attribute *attr, const char *buf, size_t count);
> +static struct kobj_attribute rxbuf_attr = __ATTR(rx_buf_value, 0660, sysfs_show, sysfs_store);

Maybe better to use a 'dgram' prefix.

> +
> struct virtio_vsock {
> 	struct virtio_device *vdev;
> 	struct virtqueue **vqs;
> @@ -360,7 +368,7 @@ virtio_transport_cancel_pkt(struct vsock_sock *vsk)
>
> static void virtio_vsock_rx_fill(struct virtio_vsock *vsock, bool is_dgram)
> {
> -	int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
> +	int buf_len = rx_buf_len;
> 	struct virtio_vsock_pkt *pkt;
> 	struct scatterlist hdr, buf, *sgs[2];
> 	struct virtqueue *vq;
> @@ -1003,6 +1011,22 @@ static struct virtio_driver virtio_vsock_driver = {
> 	.remove = virtio_vsock_remove,
> };
>
> +static ssize_t sysfs_show(struct kobject *kobj,
> +		struct kobj_attribute *attr, char *buf)
> +{
> +	return sprintf(buf, "%d", rx_buf_len);
> +}
> +
> +static ssize_t sysfs_store(struct kobject *kobj,
> +		struct kobj_attribute *attr, const char *buf, size_t count)
> +{
> +	if (kstrtou32(buf, 0, &rx_buf_len) < 0)
> +		return -EINVAL;
> +	if (rx_buf_len < 1024)
> +		rx_buf_len = 1024;
> +	return count;
> +}
> +
> static int __init virtio_vsock_init(void)
> {
> 	int ret;
> @@ -1020,8 +1044,17 @@ static int __init virtio_vsock_init(void)
> 	if (ret)
> 		goto out_vci;
>
> -	return 0;
> +	kobj_ref = kobject_create_and_add("vsock", kernel_kobj);

So, IIUC, the path will be /sys/vsock/rx_buf_value?

I'm not sure if we need to add a `virtio` subdir (e.g.
/sys/vsock/virtio/dgram_rx_buf_size)

Thanks,
Stefano

> +	/*Creating sysfs file for etx_value*/
> +	ret = sysfs_create_file(kobj_ref, &rxbuf_attr.attr);
> +	if (ret)
> +		goto out_sysfs;
> +
> +	return 0;
> +out_sysfs:
> +	kobject_put(kobj_ref);
> +	sysfs_remove_file(kernel_kobj, &rxbuf_attr.attr);
> out_vci:
> 	vsock_core_unregister(&virtio_transport.transport);
> out_wq:
> --
> 2.11.0