Hi Michael,
On 2018/12/12 23:31, Michael S. Tsirkin wrote:
> On Wed, Dec 12, 2018 at 05:31:39PM +0800, jiangyiwen wrote:
>> Guest receive mergeable rx buffer, it can merge
>> scatter rx buffer into a big buffer and then copy
>> to user space.
>>
>> In addition, it also use iovec to replace buf in struct
>> virtio_vsock_pkt, keep tx and rx consistency. The only
>> difference is now tx still uses a segment of continuous
>> physical memory to implement.
>>
>> Signed-off-by: Yiwen Jiang <jiangyiwen@xxxxxxxxxx>
>> ---
>> drivers/vhost/vsock.c | 31 +++++++---
>> include/linux/virtio_vsock.h | 6 +-
>> net/vmw_vsock/virtio_transport.c | 105 ++++++++++++++++++++++++++++----
>> net/vmw_vsock/virtio_transport_common.c | 59 ++++++++++++++----
>> 4 files changed, 166 insertions(+), 35 deletions(-)
>
>
> This was supposed to be a guest patch, why is vhost changed here?
>
In mergeable rx buff cases, it need to scatter big packets into several
buffers, so I add kvec variable in struct virtio_vsock_pkt, at the same
time, in order to keep tx and rx consistency, I use kvec to replace
variable buf, because vhost use the variable pkt->buf, so this patch
caused vhost is changed.
>> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>> index dc52b0f..c7ab0dd 100644
>> --- a/drivers/vhost/vsock.c
>> +++ b/drivers/vhost/vsock.c
>> @@ -179,6 +179,8 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
>> size_t nbytes;
>> size_t len;
>> s16 headcount;
>> + size_t remain_len;
>> + int i;
>>
>> spin_lock_bh(&vsock->send_pkt_list_lock);
>> if (list_empty(&vsock->send_pkt_list)) {
>> @@ -221,11 +223,19 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
>> break;
>> }
>>
>> - nbytes = copy_to_iter(pkt->buf, pkt->len, &iov_iter);
>> - if (nbytes != pkt->len) {
>> - virtio_transport_free_pkt(pkt);
>> - vq_err(vq, "Faulted on copying pkt buf\n");
>> - break;
>> + remain_len = pkt->len;
>> + for (i = 0; i < pkt->nr_vecs; i++) {
>> + int tmp_len;
>> +
>> + tmp_len = min(remain_len, pkt->vec[i].iov_len);
>> + nbytes = copy_to_iter(pkt->vec[i].iov_base, tmp_len, &iov_iter);
>> + if (nbytes != tmp_len) {
>> + virtio_transport_free_pkt(pkt);
>> + vq_err(vq, "Faulted on copying pkt buf\n");
>> + break;
>> + }
>> +
>> + remain_len -= tmp_len;
>> }
>>
>> vhost_add_used_n(vq, vq->heads, headcount);
>> @@ -341,6 +351,7 @@ static void vhost_transport_send_pkt_work(struct vhost_work *work)
>> struct iov_iter iov_iter;
>> size_t nbytes;
>> size_t len;
>> + void *buf;
>>
>> if (in != 0) {
>> vq_err(vq, "Expected 0 input buffers, got %u\n", in);
>> @@ -375,13 +386,17 @@ static void vhost_transport_send_pkt_work(struct vhost_work *work)
>> return NULL;
>> }
>>
>> - pkt->buf = kmalloc(pkt->len, GFP_KERNEL);
>> - if (!pkt->buf) {
>> + buf = kmalloc(pkt->len, GFP_KERNEL);
>> + if (!buf) {
>> kfree(pkt);
>> return NULL;
>> }
>>
>> - nbytes = copy_from_iter(pkt->buf, pkt->len, &iov_iter);
>> + pkt->vec[0].iov_base = buf;
>> + pkt->vec[0].iov_len = pkt->len;
>> + pkt->nr_vecs = 1;
>> +
>> + nbytes = copy_from_iter(buf, pkt->len, &iov_iter);
>> if (nbytes != pkt->len) {
>> vq_err(vq, "Expected %u byte payload, got %zu bytes\n",
>> pkt->len, nbytes);
>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>> index da9e1fe..734eeed 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_VEC_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. */
>> @@ -55,10 +57,12 @@ struct virtio_vsock_pkt {
>> struct list_head list;
>> /* socket refcnt not held, only use for cancellation */
>> struct vsock_sock *vsk;
>> - void *buf;
>> + struct kvec vec[VIRTIO_VSOCK_MAX_VEC_NUM];
>> + int nr_vecs;
>> u32 len;
>> u32 off;
>> bool reply;
>> + bool mergeable;
>> };
>>
>> struct virtio_vsock_pkt_info {
>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>> index c4a465c..148b58a 100644
>> --- a/net/vmw_vsock/virtio_transport.c
>> +++ b/net/vmw_vsock/virtio_transport.c
>> @@ -155,8 +155,10 @@ static int virtio_transport_send_pkt_loopback(struct virtio_vsock *vsock,
>>
>> sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
>> sgs[out_sg++] = &hdr;
>> - if (pkt->buf) {
>> - sg_init_one(&buf, pkt->buf, pkt->len);
>> + if (pkt->len) {
>> + /* Currently only support a segment of memory in tx */
>> + BUG_ON(pkt->vec[0].iov_len != pkt->len);
>> + sg_init_one(&buf, pkt->vec[0].iov_base, pkt->vec[0].iov_len);
>> sgs[out_sg++] = &buf;
>> }
>>
>> @@ -304,23 +306,28 @@ static int fill_old_rx_buff(struct virtqueue *vq)
>> struct virtio_vsock_pkt *pkt;
>> struct scatterlist hdr, buf, *sgs[2];
>> int ret;
>> + void *pkt_buf;
>>
>> pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
>> if (!pkt)
>> return -ENOMEM;
>>
>> - pkt->buf = kmalloc(buf_len, GFP_KERNEL);
>> - if (!pkt->buf) {
>> + pkt_buf = kmalloc(buf_len, GFP_KERNEL);
>> + if (!pkt_buf) {
>> virtio_transport_free_pkt(pkt);
>> return -ENOMEM;
>> }
>>
>> + pkt->vec[0].iov_base = pkt_buf;
>> + pkt->vec[0].iov_len = buf_len;
>> + pkt->nr_vecs = 1;
>> +
>> pkt->len = buf_len;
>>
>> sg_init_one(&hdr, &pkt->hdr, sizeof(pkt->hdr));
>> sgs[0] = &hdr;
>>
>> - sg_init_one(&buf, pkt->buf, buf_len);
>> + sg_init_one(&buf, pkt->vec[0].iov_base, buf_len);
>> sgs[1] = &buf;
>> ret = virtqueue_add_sgs(vq, sgs, 0, 2, pkt, GFP_KERNEL);
>> if (ret)
>> @@ -388,11 +395,78 @@ 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 *buf;
>> + unsigned int len;
>> + size_t vsock_hlen = sizeof(struct virtio_vsock_pkt);
>> +
>> + buf = virtqueue_get_buf(vq, &len);
>> + if (!buf)
>> + return NULL;
>> +
>> + *total_len = len;
>> + vsock->rx_buf_nr--;
>> +
>> + if (unlikely(len < vsock_hlen)) {
>> + put_page(virt_to_head_page(buf));
>> + return NULL;
>> + }
>> +
>> + pkt = buf;
>> + num_buf = le16_to_cpu(pkt->mrg_rxbuf_hdr.num_buffers);
>> + if (!num_buf || num_buf > VIRTIO_VSOCK_MAX_VEC_NUM) {
>> + put_page(virt_to_head_page(buf));
>> + return NULL;
>> + }
>
> So everything just stops going, and host and user don't even
> know what the reason is. And not only that - the next
> packet will be corrupted because we skipped the first one.
>
>
I understand this case will not encountered unless the code has
*BUG*, like Host send some problematic packages (shorten/longer than
expected). In this case, I think we should ignore/drop these packets.
>
>> +
>> + /* Initialize pkt residual structure */
>> + memset(&pkt->work, 0, vsock_hlen - sizeof(struct virtio_vsock_hdr) -
>> + sizeof(struct virtio_vsock_mrg_rxbuf_hdr));
>> +
>> + pkt->mergeable = true;
>> + pkt->len = le32_to_cpu(pkt->hdr.len);
>> + if (!pkt->len)
>> + return pkt;
>> +
>> + len -= vsock_hlen;
>> + if (len) {
>> + pkt->vec[pkt->nr_vecs].iov_base = buf + vsock_hlen;
>> + pkt->vec[pkt->nr_vecs].iov_len = len;
>> + /* Shared page with pkt, so get page in advance */
>> + get_page(virt_to_head_page(buf));
>> + pkt->nr_vecs++;
>> + }
>> +
>> + while (--num_buf) {
>> + buf = virtqueue_get_buf(vq, &len);
>> + if (!buf)
>> + goto err;
>> +
>> + *total_len += len;
>> + vsock->rx_buf_nr--;
>> +
>> + pkt->vec[pkt->nr_vecs].iov_base = buf;
>> + pkt->vec[pkt->nr_vecs].iov_len = len;
>> + pkt->nr_vecs++;
>> + }
>> +
>> + return pkt;
>> +err:
>> + virtio_transport_free_pkt(pkt);
>> + return NULL;
>> +}
>> +
>> 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];
>>
>> @@ -412,21 +486,26 @@ 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;
>> + } else {
>> + pkt = virtqueue_get_buf(vq, &len);
>> + if (!pkt)
>> + break;
>>
>
> So looking at it, this seems to be the main source of the gain.
> But why does this require host/guest changes?
>
>
> The way I see it:
> - get a buffer and create an skb
> - get the next one, check header matches, if yes
> tack it on the skb as a fragment. If not then
> don't, deliver previous one and queue the new one.
>
>
Vhost change reason I explain as above, and I hope use kvec
to instead buf, after all buf only can express a contiguous
physical memory.
Thanks,
Yiwen.
>
>> - vsock->rx_buf_nr--;
>> + 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..123a8b6 100644
>> --- a/net/vmw_vsock/virtio_transport_common.c
>> +++ b/net/vmw_vsock/virtio_transport_common.c
>> @@ -44,6 +44,7 @@ static const struct virtio_transport *virtio_transport_get_ops(void)
>> {
>> struct virtio_vsock_pkt *pkt;
>> int err;
>> + void *buf = NULL;
>>
>> pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
>> if (!pkt)
>> @@ -62,12 +63,16 @@ static const struct virtio_transport *virtio_transport_get_ops(void)
>> pkt->vsk = info->vsk;
>>
>> if (info->msg && len > 0) {
>> - pkt->buf = kmalloc(len, GFP_KERNEL);
>> - if (!pkt->buf)
>> + buf = kmalloc(len, GFP_KERNEL);
>> + if (!buf)
>> goto out_pkt;
>> - err = memcpy_from_msg(pkt->buf, info->msg, len);
>> + err = memcpy_from_msg(buf, info->msg, len);
>> if (err)
>> goto out;
>> +
>> + pkt->vec[0].iov_base = buf;
>> + pkt->vec[0].iov_len = len;
>> + pkt->nr_vecs = 1;
>> }
>>
>> trace_virtio_transport_alloc_pkt(src_cid, src_port,
>> @@ -80,7 +85,7 @@ static const struct virtio_transport *virtio_transport_get_ops(void)
>> return pkt;
>>
>> out:
>> - kfree(pkt->buf);
>> + kfree(buf);
>> out_pkt:
>> kfree(pkt);
>> return NULL;
>> @@ -92,6 +97,7 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
>> struct virtio_vsock_pkt *pkt = opaque;
>> struct af_vsockmon_hdr *hdr;
>> struct sk_buff *skb;
>> + int i;
>>
>> skb = alloc_skb(sizeof(*hdr) + sizeof(pkt->hdr) + pkt->len,
>> GFP_ATOMIC);
>> @@ -134,7 +140,8 @@ static struct sk_buff *virtio_transport_build_skb(void *opaque)
>> skb_put_data(skb, &pkt->hdr, sizeof(pkt->hdr));
>>
>> if (pkt->len) {
>> - skb_put_data(skb, pkt->buf, pkt->len);
>> + for (i = 0; i < pkt->nr_vecs; i++)
>> + skb_put_data(skb, pkt->vec[i].iov_base, pkt->vec[i].iov_len);
>> }
>>
>> return skb;
>> @@ -260,6 +267,9 @@ static int virtio_transport_send_credit_update(struct vsock_sock *vsk,
>>
>> spin_lock_bh(&vvs->rx_lock);
>> while (total < len && !list_empty(&vvs->rx_queue)) {
>> + size_t copy_bytes, last_vec_total = 0, vec_off;
>> + int i;
>> +
>> pkt = list_first_entry(&vvs->rx_queue,
>> struct virtio_vsock_pkt, list);
>>
>> @@ -272,14 +282,28 @@ 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;
>> + for (i = 0; i < pkt->nr_vecs; i++) {
>> + if (pkt->off > last_vec_total + pkt->vec[i].iov_len) {
>> + last_vec_total += pkt->vec[i].iov_len;
>> + continue;
>> + }
>> +
>> + vec_off = pkt->off - last_vec_total;
>> + copy_bytes = min(pkt->vec[i].iov_len - vec_off, bytes);
>> + err = memcpy_to_msg(msg, pkt->vec[i].iov_base + vec_off,
>> + copy_bytes);
>> + if (err)
>> + goto out;
>> +
>> + bytes -= copy_bytes;
>> + pkt->off += copy_bytes;
>> + total += copy_bytes;
>> + last_vec_total += pkt->vec[i].iov_len;
>> + if (!bytes)
>> + break;
>> + }
>>
>> 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 +1074,17 @@ 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 = 0; i < pkt->nr_vecs; i++)
>> + put_page(virt_to_head_page(pkt->vec[i].iov_base));
>> + put_page(virt_to_head_page((void *)pkt));
>> + } else {
>> + for (i = 0; i < pkt->nr_vecs; i++)
>> + kfree(pkt->vec[i].iov_base);
>> + kfree(pkt);
>> + }
>> }
>> EXPORT_SYMBOL_GPL(virtio_transport_free_pkt);
>>
>> --
>> 1.8.3.1
>>
>
> .
>
