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Date: Tue, 15 Oct 2019 09:57:11 +0900
From: Prashant Bhole <prashantbhole.linux@...il.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jason Wang <jasowang@...hat.com>,
"David S . Miller" <davem@...emloft.net>,
David Ahern <dsahern@...il.com>, kvm@...r.kernel.org,
netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] vhost_net: user tap recvmsg api to access
ptr ring
Hi Michael,
Thanks for reviewing.
On 10/13/19 5:41 AM, Michael S. Tsirkin wrote:
> On Sat, Oct 12, 2019 at 10:53:56AM +0900, prashantbhole.linux@...il.com wrote:
>> From: Prashant Bhole <prashantbhole.linux@...il.com>
>>
>> Currently vhost_net directly accesses ptr ring of tap driver to
>> fetch Rx packet pointers. In order to avoid it this patch modifies
>> tap driver's recvmsg api to do additional task of fetching Rx packet
>> pointers.
>>
>> A special struct tun_msg_ctl is already being usedd via msg_control
>> for tun Rx XDP batching. This patch extends tun_msg_ctl usage to
>> send sub commands to recvmsg api. recvmsg can now produce/unproduce
>> pointers from ptr ring as an additional task.
>>
>> This will be useful in future in implementation of virtio-net XDP
>> offload feature. Where packets will be XDP batch processed in
>> tun_recvmsg.
>
> I'd like to see that future patch, by itself this patchset
> seems to be of limited usefulness.
Agree, this set is just a reorganization. Next time this will be a part
of set which actually uses it.
Thanks
>
>> Signed-off-by: Prashant Bhole <prashantbhole.linux@...il.com>
>> ---
>> drivers/net/tap.c | 22 +++++++++++++++++++-
>> drivers/net/tun.c | 24 +++++++++++++++++++++-
>> drivers/vhost/net.c | 46 +++++++++++++++++++++++++++++++++---------
>> include/linux/if_tun.h | 3 +++
>> 4 files changed, 83 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/tap.c b/drivers/net/tap.c
>> index 01bd260ce60c..3d0bf382dbbc 100644
>> --- a/drivers/net/tap.c
>> +++ b/drivers/net/tap.c
>> @@ -1234,8 +1234,28 @@ static int tap_recvmsg(struct socket *sock, struct msghdr *m,
>> size_t total_len, int flags)
>> {
>> struct tap_queue *q = container_of(sock, struct tap_queue, sock);
>> - struct sk_buff *skb = m->msg_control;
>> + struct tun_msg_ctl *ctl = m->msg_control;
>> + struct sk_buff *skb = NULL;
>> int ret;
>> +
>> + if (ctl) {
>> + switch (ctl->cmd) {
>> + case TUN_CMD_PACKET:
>> + skb = ctl->ptr;
>> + break;
>> + case TUN_CMD_PRODUCE_PTRS:
>> + return ptr_ring_consume_batched(&q->ring,
>> + ctl->ptr_array,
>> + ctl->num);
>> + case TUN_CMD_UNPRODUCE_PTRS:
>> + ptr_ring_unconsume(&q->ring, ctl->ptr_array, ctl->num,
>> + tun_ptr_free);
>> + return 0;
>> + default:
>> + return -EINVAL;
>> + }
>> + }
>> +
>> if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
>> kfree_skb(skb);
>> return -EINVAL;
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index 29711671959b..7d4886f53389 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -2577,7 +2577,8 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
>> {
>> struct tun_file *tfile = container_of(sock, struct tun_file, socket);
>> struct tun_struct *tun = tun_get(tfile);
>> - void *ptr = m->msg_control;
>> + struct tun_msg_ctl *ctl = m->msg_control;
>> + void *ptr = NULL;
>> int ret;
>>
>> if (!tun) {
>> @@ -2585,6 +2586,27 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
>> goto out_free;
>> }
>>
>> + if (ctl) {
>> + switch (ctl->cmd) {
>> + case TUN_CMD_PACKET:
>> + ptr = ctl->ptr;
>> + break;
>> + case TUN_CMD_PRODUCE_PTRS:
>> + ret = ptr_ring_consume_batched(&tfile->tx_ring,
>> + ctl->ptr_array,
>> + ctl->num);
>> + goto out;
>> + case TUN_CMD_UNPRODUCE_PTRS:
>> + ptr_ring_unconsume(&tfile->tx_ring, ctl->ptr_array,
>> + ctl->num, tun_ptr_free);
>> + ret = 0;
>> + goto out;
>> + default:
>> + ret = -EINVAL;
>> + goto out_put_tun;
>> + }
>> + }
>> +
>> if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) {
>> ret = -EINVAL;
>> goto out_put_tun;
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index 5946d2775bd0..5e5c1063606c 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -175,24 +175,44 @@ static void *vhost_net_buf_consume(struct vhost_net_buf *rxq)
>>
>> static int vhost_net_buf_produce(struct vhost_net_virtqueue *nvq)
>> {
>> + struct vhost_virtqueue *vq = &nvq->vq;
>> + struct socket *sock = vq->private_data;
>> struct vhost_net_buf *rxq = &nvq->rxq;
>> + struct tun_msg_ctl ctl = {
>> + .cmd = TUN_CMD_PRODUCE_PTRS,
>> + .ptr_array = rxq->queue,
>> + .num = VHOST_NET_BATCH,
>> + };
>> + struct msghdr msg = {
>> + .msg_control = &ctl,
>> + };
>>
>> rxq->head = 0;
>> - rxq->tail = ptr_ring_consume_batched(nvq->rx_ring, rxq->queue,
>> - VHOST_NET_BATCH);
>> + rxq->tail = sock->ops->recvmsg(sock, &msg, 0, 0);
>> + if (rxq->tail < 0)
>> + rxq->tail = 0;
>> +
>> return rxq->tail;
>> }
>>
>> static void vhost_net_buf_unproduce(struct vhost_net_virtqueue *nvq)
>> {
>> + struct vhost_virtqueue *vq = &nvq->vq;
>> + struct socket *sock = vq->private_data;
>> struct vhost_net_buf *rxq = &nvq->rxq;
>> + struct tun_msg_ctl ctl = {
>> + .cmd = TUN_CMD_UNPRODUCE_PTRS,
>> + .ptr_array = rxq->queue + rxq->head,
>> + .num = vhost_net_buf_get_size(rxq),
>> + };
>> + struct msghdr msg = {
>> + .msg_control = &ctl,
>> + };
>>
>> - if (nvq->rx_ring && !vhost_net_buf_is_empty(rxq)) {
>> - ptr_ring_unconsume(nvq->rx_ring, rxq->queue + rxq->head,
>> - vhost_net_buf_get_size(rxq),
>> - tun_ptr_free);
>> - rxq->head = rxq->tail = 0;
>> - }
>> + if (!vhost_net_buf_is_empty(rxq))
>> + sock->ops->recvmsg(sock, &msg, 0, 0);
>> +
>> + rxq->head = rxq->tail = 0;
>> }
>>
>> static int vhost_net_buf_peek_len(void *ptr)
>> @@ -1109,6 +1129,9 @@ static void handle_rx(struct vhost_net *net)
>> .flags = 0,
>> .gso_type = VIRTIO_NET_HDR_GSO_NONE
>> };
>> + struct tun_msg_ctl ctl = {
>> + .cmd = TUN_CMD_PACKET,
>> + };
>> size_t total_len = 0;
>> int err, mergeable;
>> s16 headcount;
>> @@ -1166,8 +1189,11 @@ static void handle_rx(struct vhost_net *net)
>> goto out;
>> }
>> busyloop_intr = false;
>> - if (nvq->rx_ring)
>> - msg.msg_control = vhost_net_buf_consume(&nvq->rxq);
>> + if (nvq->rx_ring) {
>> + ctl.cmd = TUN_CMD_PACKET;
>> + ctl.ptr = vhost_net_buf_consume(&nvq->rxq);
>> + msg.msg_control = &ctl;
>> + }
>> /* On overrun, truncate and discard */
>> if (unlikely(headcount > UIO_MAXIOV)) {
>> iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1);
>> diff --git a/include/linux/if_tun.h b/include/linux/if_tun.h
>> index bdfa671612db..8608d4095143 100644
>> --- a/include/linux/if_tun.h
>> +++ b/include/linux/if_tun.h
>> @@ -13,10 +13,13 @@
>>
>> #define TUN_CMD_PACKET 1
>> #define TUN_CMD_BATCH 2
>> +#define TUN_CMD_PRODUCE_PTRS 3
>> +#define TUN_CMD_UNPRODUCE_PTRS 4
>> struct tun_msg_ctl {
>> unsigned short cmd;
>> unsigned short num;
>> void *ptr;
>> + void **ptr_array;
>> };
>>
>> struct tun_xdp_hdr {
>> --
>> 2.21.0
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