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Date: Tue, 6 Nov 2018 14:41:54 +0800
From: jiangyiwen <jiangyiwen@...wei.com>
To: Jason Wang <jasowang@...hat.com>, <stefanha@...hat.com>
CC: <netdev@...r.kernel.org>, <kvm@...r.kernel.org>,
<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 3/5] VSOCK: support receive mergeable rx buffer in guest
On 2018/11/6 12:00, Jason Wang wrote:
>
> On 2018/11/5 下午3:47, jiangyiwen wrote:
>> Guest receive mergeable rx buffer, it can merge
>> scatter rx buffer into a big buffer and then copy
>> to user space.
>>
>> Signed-off-by: Yiwen Jiang <jiangyiwen@...wei.com>
>> ---
>> include/linux/virtio_vsock.h | 9 ++++
>> net/vmw_vsock/virtio_transport.c | 75 +++++++++++++++++++++++++++++----
>> net/vmw_vsock/virtio_transport_common.c | 59 ++++++++++++++++++++++----
>> 3 files changed, 127 insertions(+), 16 deletions(-)
>>
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index da9e1fe..6be3cd7 100644
>> --- a/include/linux/virtio_vsock.h
>> +++ b/include/linux/virtio_vsock.h
>> @@ -13,6 +13,8 @@
>> #define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE (1024 * 4)
>> #define VIRTIO_VSOCK_MAX_BUF_SIZE 0xFFFFFFFFUL
>> #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE (1024 * 64)
>> +/* virtio_vsock_pkt + max_pkt_len(default MAX_PKT_BUF_SIZE) */
>> +#define VIRTIO_VSOCK_MAX_MRG_BUF_NUM ((VIRTIO_VSOCK_MAX_PKT_BUF_SIZE / PAGE_SIZE) + 1)
>>
>> /* Virtio-vsock feature */
>> #define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */
>> @@ -48,6 +50,11 @@ struct virtio_vsock_sock {
>> struct list_head rx_queue;
>> };
>>
>> +struct virtio_vsock_mrg_rxbuf {
>> + void *buf;
>> + u32 len;
>> +};
>> +
>> struct virtio_vsock_pkt {
>> struct virtio_vsock_hdr hdr;
>> struct virtio_vsock_mrg_rxbuf_hdr mrg_rxbuf_hdr;
>> @@ -59,6 +66,8 @@ struct virtio_vsock_pkt {
>> u32 len;
>> u32 off;
>> bool reply;
>> + bool mergeable;
>> + struct virtio_vsock_mrg_rxbuf mrg_rxbuf[VIRTIO_VSOCK_MAX_MRG_BUF_NUM];
>> };
>
>
> It's better to use iov here I think, and drop buf completely.
>
> And this is better to be done in an independent patch.
>
You're right, I can use kvec instead of customized structure,
in addition, I don't understand about drop buf completely and
an independent patch.
Thanks.
>
>>
>> struct virtio_vsock_pkt_info {
>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> index 2040a9e..3557ad3 100644
>> --- a/net/vmw_vsock/virtio_transport.c
>> +++ b/net/vmw_vsock/virtio_transport.c
>> @@ -359,11 +359,62 @@ static bool virtio_transport_more_replies(struct virtio_vsock *vsock)
>> return val < virtqueue_get_vring_size(vq);
>> }
>>
>> +static struct virtio_vsock_pkt *receive_mergeable(struct virtqueue *vq,
>> + struct virtio_vsock *vsock, unsigned int *total_len)
>> +{
>> + struct virtio_vsock_pkt *pkt;
>> + u16 num_buf;
>> + void *page;
>> + unsigned int len;
>> + int i = 0;
>> +
>> + page = virtqueue_get_buf(vq, &len);
>> + if (!page)
>> + return NULL;
>> +
>> + *total_len = len;
>> + vsock->rx_buf_nr--;
>> +
>> + pkt = page;
>> + num_buf = le16_to_cpu(pkt->mrg_rxbuf_hdr.num_buffers);
>> + if (!num_buf || num_buf > VIRTIO_VSOCK_MAX_MRG_BUF_NUM)
>> + goto err;
>> +
>> + pkt->mergeable = true;
>> + if (!le32_to_cpu(pkt->hdr.len))
>> + return pkt;
>> +
>> + len -= sizeof(struct virtio_vsock_pkt);
>> + pkt->mrg_rxbuf[i].buf = page + sizeof(struct virtio_vsock_pkt);
>> + pkt->mrg_rxbuf[i].len = len;
>> + i++;
>> +
>> + while (--num_buf) {
>> + page = virtqueue_get_buf(vq, &len);
>> + if (!page)
>> + goto err;
>> +
>> + *total_len += len;
>> + vsock->rx_buf_nr--;
>> +
>> + pkt->mrg_rxbuf[i].buf = page;
>> + pkt->mrg_rxbuf[i].len = len;
>> + i++;
>> + }
>> +
>> + return pkt;
>> +err:
>> + virtio_transport_free_pkt(pkt);
>> + return NULL;
>> +}
>
>
> Similar logic could be found at virtio-net driver.
>
> Haven't thought this deeply, but it looks to me use virtio-net driver is also possible, e.g for data-path, just register vsock specific callbacks.
>
>
>> +
>> static void virtio_transport_rx_work(struct work_struct *work)
>> {
>> struct virtio_vsock *vsock =
>> container_of(work, struct virtio_vsock, rx_work);
>> struct virtqueue *vq;
>> + size_t vsock_hlen = vsock->mergeable ? sizeof(struct virtio_vsock_pkt) :
>> + sizeof(struct virtio_vsock_hdr);
>>
>> vq = vsock->vqs[VSOCK_VQ_RX];
>>
>> @@ -383,21 +434,29 @@ static void virtio_transport_rx_work(struct work_struct *work)
>> goto out;
>> }
>>
>> - pkt = virtqueue_get_buf(vq, &len);
>> - if (!pkt) {
>> - break;
>> - }
>> + if (likely(vsock->mergeable)) {
>> + pkt = receive_mergeable(vq, vsock, &len);
>> + if (!pkt)
>> + break;
>>
>> - vsock->rx_buf_nr--;
>> + pkt->len = le32_to_cpu(pkt->hdr.len);
>> + } else {
>> + pkt = virtqueue_get_buf(vq, &len);
>> + if (!pkt) {
>> + break;
>> + }
>> +
>> + vsock->rx_buf_nr--;
>> + }
>>
>> /* Drop short/long packets */
>> - if (unlikely(len < sizeof(pkt->hdr) ||
>> - len > sizeof(pkt->hdr) + pkt->len)) {
>> + if (unlikely(len < vsock_hlen ||
>> + len > vsock_hlen + pkt->len)) {
>> virtio_transport_free_pkt(pkt);
>> continue;
>> }
>>
>> - pkt->len = len - sizeof(pkt->hdr);
>> + pkt->len = len - vsock_hlen;
>> virtio_transport_deliver_tap_pkt(pkt);
>> virtio_transport_recv_pkt(pkt);
>> }
>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>> index 3ae3a33..7bef1d5 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -272,14 +272,49 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk,
>> */
>> spin_unlock_bh(&vvs->rx_lock);
>>
>> - err = memcpy_to_msg(msg, pkt->buf + pkt->off, bytes);
>> - if (err)
>> - goto out;
>> + if (pkt->mergeable) {
>> + struct virtio_vsock_mrg_rxbuf *buf = pkt->mrg_rxbuf;
>> + size_t mrg_copy_bytes, last_buf_total = 0, rxbuf_off;
>> + size_t tmp_bytes = bytes;
>> + int i;
>> +
>> + for (i = 0; i < le16_to_cpu(pkt->mrg_rxbuf_hdr.num_buffers); i++) {
>> + if (pkt->off > last_buf_total + buf[i].len) {
>> + last_buf_total += buf[i].len;
>> + continue;
>> + }
>> +
>> + rxbuf_off = pkt->off - last_buf_total;
>> + mrg_copy_bytes = min(buf[i].len - rxbuf_off, tmp_bytes);
>> + err = memcpy_to_msg(msg, buf[i].buf + rxbuf_off, mrg_copy_bytes);
>> + if (err)
>> + goto out;
>> +
>> + tmp_bytes -= mrg_copy_bytes;
>> + pkt->off += mrg_copy_bytes;
>> + last_buf_total += buf[i].len;
>> + if (!tmp_bytes)
>> + break;
>> + }
>
>
> After switch to use iov, you can user iov_iter helper to avoid the above open-coding I believe.
>
> And you can also drop the if (mergeable) condition.
>
> Thanks
>
Thanks, I will try to use iov instead.
>
>> +
>> + if (tmp_bytes) {
>> + printk(KERN_WARNING "WARNING! bytes = %llu, "
>> + "bytes = %llu\n",
>> + (unsigned long long)bytes,
>> + (unsigned long long)tmp_bytes);
>> + }
>> +
>> + total += (bytes - tmp_bytes);
>> + } else {
>> + err = memcpy_to_msg(msg, pkt->buf + pkt->off, bytes);
>> + if (err)
>> + goto out;
>> +
>> + total += bytes;
>> + pkt->off += bytes;
>> + }
>>
>> spin_lock_bh(&vvs->rx_lock);
>> -
>> - total += bytes;
>> - pkt->off += bytes;
>> if (pkt->off == pkt->len) {
>> virtio_transport_dec_rx_pkt(vvs, pkt);
>> list_del(&pkt->list);
>> @@ -1050,8 +1085,16 @@ void virtio_transport_recv_pkt(struct virtio_vsock_pkt *pkt)
>>
>> void virtio_transport_free_pkt(struct virtio_vsock_pkt *pkt)
>> {
>> - kfree(pkt->buf);
>> - kfree(pkt);
>> + int i;
>> +
>> + if (pkt->mergeable) {
>> + for (i = 1; i < le16_to_cpu(pkt->mrg_rxbuf_hdr.num_buffers); i++)
>> + free_page((unsigned long)pkt->mrg_rxbuf[i].buf);
>> + free_page((unsigned long)(void *)pkt);
>> + } else {
>> + kfree(pkt->buf);
>> + kfree(pkt);
>> + }
>> }
>> EXPORT_SYMBOL_GPL(virtio_transport_free_pkt);
>>
>
> .
>
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