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Date: Tue, 6 Nov 2018 12:00:45 +0800
From: Jason Wang <jasowang@...hat.com>
To: jiangyiwen <jiangyiwen@...wei.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 2018/11/5 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.
>
> 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
> +
> + 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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