[PATCH v2 8/8] vsock/virtio: make the RX buffer size tunable

Stefano Garzarella
2019-05-10T12:59:43Z

The RX buffer size determines the memory consumption of the
vsock/virtio guest driver, so we make it tunable through
a module parameter.

The size allowed are between 4 KB and 64 KB in order to be
compatible with old host drivers.

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
include/linux/virtio_vsock.h | 1 +
net/vmw_vsock/virtio_transport.c | 27 ++++++++++++++++++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index 5a9d25be72df..b9f8c3d91f80 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h
@@ -13,6 +13,7 @@
#define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 64)
#define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL
#define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64)
+#define VIRTIO_VSOCK_MIN_PKT_BUF_SIZE (1024 * 4)

enum {
VSOCK_VQ_RX = 0, /* for host to guest data */
diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
index af1d2ce12f54..732398b4e28f 100644
--- a/net/vmw_vsock/virtio_transport.c
+++ b/net/vmw_vsock/virtio_transport.c
@@ -66,6 +66,31 @@ struct virtio_vsock {
u32 guest_cid;
};

+static unsigned int rx_buf_size = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
+
+static int param_set_rx_buf_size(const char *val, const struct kernel_param *kp)
+{
+ unsigned int size;
+ int ret;
+
+ ret = kstrtouint(val, 0, &size);
+ if (ret)
+ return ret;
+
+ if (size < VIRTIO_VSOCK_MIN_PKT_BUF_SIZE ||
+ size > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
+ return -EINVAL;
+
+ return param_set_uint(val, kp);
+};
+
+static const struct kernel_param_ops param_ops_rx_buf_size = {
+ .set = param_set_rx_buf_size,
+ .get = param_get_uint,
+};
+
+module_param_cb(rx_buf_size, &param_ops_rx_buf_size, &rx_buf_size, 0644);
+
static struct virtio_vsock *virtio_vsock_get(void)
{
return the_virtio_vsock;
@@ -261,7 +286,7 @@ virtio_transport_cancel_pkt(struct vsock_sock *vsk)

static void virtio_vsock_rx_fill(struct virtio_vsock *vsock)
{
- int buf_len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
+ int buf_len = rx_buf_size;
struct virtio_vsock_pkt *pkt;
struct scatterlist hdr, buf, *sgs[2];
struct virtqueue *vq;
--
2.20.1