On 22.05.2023 16:11, Simon Horman wrote:
> On Mon, May 22, 2023 at 10:39:38AM +0300, Arseniy Krasnov wrote:
>> This adds handling of MSG_ZEROCOPY flag on transmission path: if this
>> flag is set and zerocopy transmission is possible, then non-linear skb
>> will be created and filled with the pages of user's buffer. Pages of
>> user's buffer are locked in memory by 'get_user_pages()'.
>>
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
>> ---
>> net/vmw_vsock/virtio_transport_common.c | 305 +++++++++++++++++++-----
>> 1 file changed, 243 insertions(+), 62 deletions(-)
>>
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 9854f48a0544..5acf824afe41 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -37,73 +37,161 @@ virtio_transport_get_ops(struct vsock_sock *vsk)
>> return container_of(t, struct virtio_transport, transport);
>> }
>>
>> -/* Returns a new packet on success, otherwise returns NULL.
>> - *
>> - * If NULL is returned, errp is set to a negative errno.
>> - */
>> -static struct sk_buff *
>> -virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
>> - size_t len,
>> - u32 src_cid,
>> - u32 src_port,
>> - u32 dst_cid,
>> - u32 dst_port)
>> -{
>> - const size_t skb_len = VIRTIO_VSOCK_SKB_HEADROOM + len;
>> - struct virtio_vsock_hdr *hdr;
>> - struct sk_buff *skb;
>> - void *payload;
>> - int err;
>> +static bool virtio_transport_can_zcopy(struct virtio_vsock_pkt_info *info,
>> + size_t max_to_send)
>> +{
>> + struct iov_iter *iov_iter;
>> + size_t max_skb_cap;
>> + size_t bytes;
>> + int i;
>>
>> - skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
>> - if (!skb)
>> - return NULL;
>> + if (!info->msg)
>> + return false;
>>
>> - hdr = virtio_vsock_hdr(skb);
>> - hdr->type = cpu_to_le16(info->type);
>> - hdr->op = cpu_to_le16(info->op);
>> - hdr->src_cid = cpu_to_le64(src_cid);
>> - hdr->dst_cid = cpu_to_le64(dst_cid);
>> - hdr->src_port = cpu_to_le32(src_port);
>> - hdr->dst_port = cpu_to_le32(dst_port);
>> - hdr->flags = cpu_to_le32(info->flags);
>> - hdr->len = cpu_to_le32(len);
>> + if (!(info->flags & MSG_ZEROCOPY) && !info->msg->msg_ubuf)
>> + return false;
>>
>> - if (info->msg && len > 0) {
>> - payload = skb_put(skb, len);
>> - err = memcpy_from_msg(payload, info->msg, len);
>> - if (err)
>> - goto out;
>> + iov_iter = &info->msg->msg_iter;
>> +
>> + if (iter_is_ubuf(iov_iter)) {
>> + if (offset_in_page(iov_iter->ubuf))
>> + return false;
>> +
>> + return true;
>> + }
>> +
>> + if (!iter_is_iovec(iov_iter))
>> + return false;
>> +
>> + if (iov_iter->iov_offset)
>> + return false;
>> +
>> + /* We can't send whole iov. */
>> + if (iov_iter->count > max_to_send)
>> + return false;
>> +
>> + for (bytes = 0, i = 0; i < iov_iter->nr_segs; i++) {
>> + const struct iovec *iovec;
>> + int pages_in_elem;
>> +
>> + iovec = &iov_iter->__iov[i];
>> +
>> + /* Base must be page aligned. */
>> + if (offset_in_page(iovec->iov_base))
>> + return false;
>>
>> - if (msg_data_left(info->msg) == 0 &&
>> - info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
>> - hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
>> + /* Only last element could have non page aligned size. */
>> + if (i != (iov_iter->nr_segs - 1)) {
>> + if (offset_in_page(iovec->iov_len))
>> + return false;
>>
>> - if (info->msg->msg_flags & MSG_EOR)
>> - hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
>> + pages_in_elem = iovec->iov_len >> PAGE_SHIFT;
>> + } else {
>> + pages_in_elem = round_up(iovec->iov_len, PAGE_SIZE);
>> + pages_in_elem >>= PAGE_SHIFT;
>> }
>> +
>> + bytes += (pages_in_elem * PAGE_SIZE);
>> }
>
> Hi Arseniy,
>
> bytes is set but the loop above, but seems otherwise unused in this function.
>
>>
>> - if (info->reply)
>> - virtio_vsock_skb_set_reply(skb);
>> + /* How many bytes we can pack to single skb. Maximum packet
>> + * buffer size is needed to allow vhost handle such packets,
>> + * otherwise they will be dropped.
>> + */
>> + max_skb_cap = min((unsigned int)(MAX_SKB_FRAGS * PAGE_SIZE),
>> + (unsigned int)VIRTIO_VSOCK_MAX_PKT_BUF_SIZE);
>
> Likewise, max_skb_cap seems to be set but unused in this function.
>
Exactly! Seems I forgot to remove it since v2. Thanks for this and above!
>>
>> - trace_virtio_transport_alloc_pkt(src_cid, src_port,
>> - dst_cid, dst_port,
>> - len,
>> - info->type,
>> - info->op,
>> - info->flags);
>> + return true;
>> +}
>
> ...
