diff mbox series

[RFC,v3,05/17] vsock/virtio: MSG_ZEROCOPY flag support

Message ID 20230522073950.3574171-6-AVKrasnov@sberdevices.ru (mailing list archive)
State New, archived
Headers show
Series vsock: MSG_ZEROCOPY flag support | expand

Commit Message

Arseniy Krasnov May 22, 2023, 7:39 a.m. UTC 
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@sberdevices.ru>
---
 net/vmw_vsock/virtio_transport_common.c | 305 +++++++++++++++++++-----
 1 file changed, 243 insertions(+), 62 deletions(-)

Comments

Arseniy Krasnov May 22, 2023, 1:09 p.m. UTC | #1 
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@sberdevices.ru>
>> ---
>>  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;
>> +}
> 
> ...
Simon Horman May 22, 2023, 1:11 p.m. UTC | #2 
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@sberdevices.ru>
> ---
>  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.

>  
> -	trace_virtio_transport_alloc_pkt(src_cid, src_port,
> -					 dst_cid, dst_port,
> -					 len,
> -					 info->type,
> -					 info->op,
> -					 info->flags);
> +	return true;
> +}

...
Arseniy Krasnov May 23, 2023, 5:46 a.m. UTC | #3 
On 22.05.2023 16:09, Arseniy Krasnov wrote:
> 
> 
> 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@sberdevices.ru>
>>> ---
>>>  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);

^^^
This alignment (base and length) checks are not needed, because virtio supports unaligned buffers. I'll remove
it in v4.

Thanks, Arseniy

>>>  	}
>>
>> 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;
>>> +}
>>
>> ...
diff mbox series

Patch

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);
 	}
 
-	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);
 
-	trace_virtio_transport_alloc_pkt(src_cid, src_port,
-					 dst_cid, dst_port,
-					 len,
-					 info->type,
-					 info->op,
-					 info->flags);
+	return true;
+}
 
-	if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) {
-		WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n");
-		goto out;
+static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,
+					   struct sk_buff *skb,
+					   struct msghdr *msg,
+					   bool zerocopy)
+{
+	struct ubuf_info *uarg;
+
+	if (msg->msg_ubuf) {
+		uarg = msg->msg_ubuf;
+		net_zcopy_get(uarg);
+	} else {
+		struct iov_iter *iter = &msg->msg_iter;
+		struct ubuf_info_msgzc *uarg_zc;
+		int len;
+
+		/* Only ITER_IOVEC or ITER_UBUF are allowed and
+		 * checked before.
+		 */
+		if (iter_is_iovec(iter))
+			len = iov_length(iter->__iov, iter->nr_segs);
+		else
+			len = iter->count;
+
+		uarg = msg_zerocopy_realloc(sk_vsock(vsk),
+					    len,
+					    NULL);
+
+		if (!uarg)
+			return -1;
+
+		uarg_zc = uarg_to_msgzc(uarg);
+		uarg_zc->zerocopy = zerocopy ? 1 : 0;
 	}
 
-	return skb;
+	skb_zcopy_init(skb, uarg);
 
-out:
-	kfree_skb(skb);
-	return NULL;
+	return 0;
+}
+
+static int virtio_transport_fill_linear_skb(struct sk_buff *skb,
+					    struct vsock_sock *vsk,
+					    struct virtio_vsock_pkt_info *info,
+					    size_t len)
+{
+	void *payload;
+	int err;
+
+	payload = skb_put(skb, len);
+	err = memcpy_from_msg(payload, info->msg, len);
+	if (err)
+		return -1;
+
+	if (msg_data_left(info->msg))
+		return 0;
+
+	if (info->type == VIRTIO_VSOCK_TYPE_SEQPACKET) {
+		struct virtio_vsock_hdr *hdr;
+
+		hdr = virtio_vsock_hdr(skb);
+
+		hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOM);
+
+		if (info->msg->msg_flags & MSG_EOR)
+			hdr->flags |= cpu_to_le32(VIRTIO_VSOCK_SEQ_EOR);
+	}
+
+	return 0;
+}
+
+static void virtio_transport_init_hdr(struct sk_buff *skb,
+				      struct virtio_vsock_pkt_info *info,
+				      u32 src_cid,
+				      u32 src_port,
+				      u32 dst_cid,
+				      u32 dst_port,
+				      size_t len)
+{
+	struct virtio_vsock_hdr *hdr;
+
+	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);
 }
 
 static void virtio_transport_copy_nonlinear_skb(struct sk_buff *skb,
@@ -214,6 +302,75 @@  static u16 virtio_transport_get_type(struct sock *sk)
 		return VIRTIO_VSOCK_TYPE_SEQPACKET;
 }
 
+/* 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 vsock_sock *vsk,
+						  struct virtio_vsock_pkt_info *info,
+						  size_t payload_len,
+						  bool zcopy,
+						  u32 dst_cid,
+						  u32 dst_port,
+						  u32 src_cid,
+						  u32 src_port)
+{
+	struct sk_buff *skb;
+	size_t skb_len;
+
+	skb_len = VIRTIO_VSOCK_SKB_HEADROOM;
+
+	if (!zcopy)
+		skb_len += payload_len;
+
+	skb = virtio_vsock_alloc_skb(skb_len, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+
+	virtio_transport_init_hdr(skb, info, src_cid, src_port,
+				  dst_cid, dst_port,
+				  payload_len);
+
+	if (info->msg && payload_len > 0) {
+		int err;
+
+		if (zcopy) {
+			struct sock *sk = sk_vsock(vsk);
+
+			err = __zerocopy_sg_from_iter(info->msg, sk, skb,
+						      &info->msg->msg_iter,
+						      payload_len);
+		} else {
+			err = virtio_transport_fill_linear_skb(skb, vsk, info, payload_len);
+		}
+
+		if (err)
+			goto out;
+
+		VIRTIO_VSOCK_SKB_CB(skb)->frag_off = 0;
+	}
+
+	if (info->reply)
+		virtio_vsock_skb_set_reply(skb);
+
+	trace_virtio_transport_alloc_pkt(src_cid, src_port,
+					 dst_cid, dst_port,
+					 payload_len,
+					 info->type,
+					 info->op,
+					 info->flags);
+
+	if (info->vsk && !skb_set_owner_sk_safe(skb, sk_vsock(info->vsk))) {
+		WARN_ONCE(1, "failed to allocate skb on vsock socket with sk_refcnt == 0\n");
+		goto out;
+	}
+
+	return skb;
+out:
+	kfree_skb(skb);
+	return NULL;
+}
+
 /* This function can only be used on connecting/connected sockets,
  * since a socket assigned to a transport is required.
  *
@@ -226,6 +383,8 @@  static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	const struct virtio_transport *t_ops;
 	struct virtio_vsock_sock *vvs;
 	u32 pkt_len = info->pkt_len;
+	bool can_zcopy = false;
+	u32 max_skb_cap;
 	u32 rest_len;
 	int ret;
 
@@ -235,6 +394,9 @@  static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	if (unlikely(!t_ops))
 		return -EFAULT;
 
+	if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY))
+		info->flags &= ~MSG_ZEROCOPY;
+
 	src_cid = t_ops->transport.get_local_cid();
 	src_port = vsk->local_addr.svm_port;
 	if (!info->remote_cid) {
@@ -254,22 +416,40 @@  static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
 		return pkt_len;
 
+	can_zcopy = virtio_transport_can_zcopy(info, pkt_len);
+	if (can_zcopy)
+		max_skb_cap = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
+				    (MAX_SKB_FRAGS * PAGE_SIZE));
+	else
+		max_skb_cap = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
+
 	rest_len = pkt_len;
 
 	do {
 		struct sk_buff *skb;
 		size_t skb_len;
 
-		skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE, rest_len);
+		skb_len = min(max_skb_cap, rest_len);
 
-		skb = virtio_transport_alloc_skb(info, skb_len,
-						 src_cid, src_port,
-						 dst_cid, dst_port);
+		skb = virtio_transport_alloc_skb(vsk, info, skb_len, can_zcopy,
+						 dst_cid, dst_port,
+						 src_cid, src_port);
 		if (!skb) {
 			ret = -ENOMEM;
 			break;
 		}
 
+		if (skb_len == rest_len &&
+		    info->flags & MSG_ZEROCOPY &&
+		    info->op == VIRTIO_VSOCK_OP_RW) {
+			if (virtio_transport_init_zcopy_skb(vsk, skb,
+							    info->msg,
+							    can_zcopy)) {
+				ret = -ENOMEM;
+				break;
+			}
+		}
+
 		virtio_transport_inc_tx_pkt(vvs, skb);
 
 		ret = t_ops->send_pkt(skb);
@@ -884,6 +1064,7 @@  virtio_transport_stream_enqueue(struct vsock_sock *vsk,
 		.msg = msg,
 		.pkt_len = len,
 		.vsk = vsk,
+		.flags = msg->msg_flags,
 	};
 
 	return virtio_transport_send_pkt_info(vsk, &info);
@@ -935,11 +1116,11 @@  static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
 	if (!t)
 		return -ENOTCONN;
 
-	reply = virtio_transport_alloc_skb(&info, 0,
-					   le64_to_cpu(hdr->dst_cid),
-					   le32_to_cpu(hdr->dst_port),
+	reply = virtio_transport_alloc_skb(NULL, &info, 0, false,
 					   le64_to_cpu(hdr->src_cid),
-					   le32_to_cpu(hdr->src_port));
+					   le32_to_cpu(hdr->src_port),
+					   le64_to_cpu(hdr->dst_cid),
+					   le32_to_cpu(hdr->dst_port));
 	if (!reply)
 		return -ENOMEM;