Linux Virtualization - Nov 2018 - [PATCH 3/5] VSOCK: support receive mergeable rx buffer in guest

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 at huawei.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];
 };

 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;
+}
+
 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;
+			}
+
+			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);

-- 
1.8.3.1

On 2018/11/5 ??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 at huawei.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);
>

On 2018/11/6 12:00, Jason Wang wrote:
> 
> On 2018/11/5 ??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 at huawei.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);
>>
> 
> .
>