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

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Date:   Fri, 18 Jun 2021 12:04:24 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Jiang Wang <jiang.wang@...edance.com>
Cc:     virtualization@...ts.linux-foundation.org, stefanha@...hat.com,
        mst@...hat.com, arseny.krasnov@...persky.com,
        jhansen@...are.comments, cong.wang@...edance.com,
        duanxiongchun@...edance.com, xieyongji@...edance.com,
        chaiwen.cc@...edance.com, Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Colin Ian King <colin.king@...onical.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>,
        Lu Wei <luwei32@...wei.com>,
        Alexander Popov <alex.popov@...ux.com>, kvm@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC v1 6/6] virtio/vsock: add sysfs for rx buf len for dgram

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@...edance.com>
>---
> 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
>