When hv_sock was originally added, __vsock_stream_recvmsg() and
vsock_stream_has_data() actually only needed to know whether there
is any readable data or not, so hvs_stream_has_data() was written to
return 1 or 0 for simplicity.

However, now hvs_stream_has_data() should return the readable bytes
because vsock_data_ready() -> vsock_stream_has_data() needs to know the
actual bytes rather than a boolean value of 1 or 0.

The SIOCINQ ioctl support also needs hvs_stream_has_data() to return
the readable bytes.

Let hvs_stream_has_data() return the readable bytes of the payload in
the next host-to-guest VMBus hv_sock packet.

Note: there may be multpile incoming hv_sock packets pending in the
VMBus channel's ringbuffer, but so far there is not a VMBus API that
allows us to know all the readable bytes in total without reading and
caching the payload of the multiple packets, so let's just return the
readable bytes of the next single packet. In the future, we'll either
add a VMBus API that allows us to know the total readable bytes without
touching the data in the ringbuffer, or the hv_sock driver needs to
understand the VMBus packet format and parse the packets directly.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>
---
 net/vmw_vsock/hyperv_transport.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
index 31342ab502b4..64f1290a9ae7 100644
--- a/net/vmw_vsock/hyperv_transport.c
+++ b/net/vmw_vsock/hyperv_transport.c
@@ -694,15 +694,25 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk, struct msghdr *msg,
 static s64 hvs_stream_has_data(struct vsock_sock *vsk)
 {
 	struct hvsock *hvs = vsk->trans;
+	bool need_refill = !hvs->recv_desc;
 	s64 ret;
 
 	if (hvs->recv_data_len > 0)
-		return 1;
+		return hvs->recv_data_len;
 
 	switch (hvs_channel_readable_payload(hvs->chan)) {
 	case 1:
-		ret = 1;
-		break;
+		if (!need_refill)
+			return -EIO;
+
+		hvs->recv_desc = hv_pkt_iter_first(hvs->chan);
+		if (!hvs->recv_desc)
+			return -ENOBUFS;
+
+		ret = hvs_update_recv_data(hvs);
+		if (ret)
+			return ret;
+		return hvs->recv_data_len;
 	case 0:
 		vsk->peer_shutdown |= SEND_SHUTDOWN;
 		ret = 0;
-- 
2.34.1

On Mon, Jun 30, 2025 at 03:57:25PM +0800, Xuewei Niu wrote:

IMO here you should not reset the author to you, but you should keep
Dexuan as authour of this patch.

>When hv_sock was originally added, __vsock_stream_recvmsg() and
>vsock_stream_has_data() actually only needed to know whether there
>is any readable data or not, so hvs_stream_has_data() was written to
>return 1 or 0 for simplicity.
>
>However, now hvs_stream_has_data() should return the readable bytes
>because vsock_data_ready() -> vsock_stream_has_data() needs to know the
>actual bytes rather than a boolean value of 1 or 0.
>
>The SIOCINQ ioctl support also needs hvs_stream_has_data() to return
>the readable bytes.
>
>Let hvs_stream_has_data() return the readable bytes of the payload in
>the next host-to-guest VMBus hv_sock packet.
>
>Note: there may be multpile incoming hv_sock packets pending in the
>VMBus channel's ringbuffer, but so far there is not a VMBus API that
>allows us to know all the readable bytes in total without reading and
>caching the payload of the multiple packets, so let's just return the
>readable bytes of the next single packet. In the future, we'll either
>add a VMBus API that allows us to know the total readable bytes without
>touching the data in the ringbuffer, or the hv_sock driver needs to
>understand the VMBus packet format and parse the packets directly.
>
>Signed-off-by: Dexuan Cui <decui@microsoft.com>
>Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>
>---
> net/vmw_vsock/hyperv_transport.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
>diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>index 31342ab502b4..64f1290a9ae7 100644
>--- a/net/vmw_vsock/hyperv_transport.c
>+++ b/net/vmw_vsock/hyperv_transport.c
>@@ -694,15 +694,25 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk, struct msghdr *msg,
> static s64 hvs_stream_has_data(struct vsock_sock *vsk)
> {
> 	struct hvsock *hvs = vsk->trans;
>+	bool need_refill = !hvs->recv_desc;

For v5 remember to fix this as Paolo suggested. Dexuan proposed a fix on 
his thread.

Stefano

> 	s64 ret;
>
> 	if (hvs->recv_data_len > 0)
>-		return 1;
>+		return hvs->recv_data_len;
>
> 	switch (hvs_channel_readable_payload(hvs->chan)) {
> 	case 1:
>-		ret = 1;
>-		break;
>+		if (!need_refill)
>+			return -EIO;
>+
>+		hvs->recv_desc = hv_pkt_iter_first(hvs->chan);
>+		if (!hvs->recv_desc)
>+			return -ENOBUFS;
>+
>+		ret = hvs_update_recv_data(hvs);
>+		if (ret)
>+			return ret;
>+		return hvs->recv_data_len;
> 	case 0:
> 		vsk->peer_shutdown |= SEND_SHUTDOWN;
> 		ret = 0;
>-- 
>2.34.1
>

> On Jul 2, 2025, at 17:58, Stefano Garzarella <sgarzare@redhat.com> wrote:
> 
> On Mon, Jun 30, 2025 at 03:57:25PM +0800, Xuewei Niu wrote:
> 
> IMO here you should not reset the author to you, but you should keep
> Dexuan as authour of this patch.

Well, I did that. However, `./scripts/checkpatch.pl` is unhappy wihtout my SOB.
Perhaps I should ignore it, and will do in the next :)  

> 
>> When hv_sock was originally added, __vsock_stream_recvmsg() and
>> vsock_stream_has_data() actually only needed to know whether there
>> is any readable data or not, so hvs_stream_has_data() was written to
>> return 1 or 0 for simplicity.
>> 
>> However, now hvs_stream_has_data() should return the readable bytes
>> because vsock_data_ready() -> vsock_stream_has_data() needs to know the
>> actual bytes rather than a boolean value of 1 or 0.
>> 
>> The SIOCINQ ioctl support also needs hvs_stream_has_data() to return
>> the readable bytes.
>> 
>> Let hvs_stream_has_data() return the readable bytes of the payload in
>> the next host-to-guest VMBus hv_sock packet.
>> 
>> Note: there may be multpile incoming hv_sock packets pending in the
>> VMBus channel's ringbuffer, but so far there is not a VMBus API that
>> allows us to know all the readable bytes in total without reading and
>> caching the payload of the multiple packets, so let's just return the
>> readable bytes of the next single packet. In the future, we'll either
>> add a VMBus API that allows us to know the total readable bytes without
>> touching the data in the ringbuffer, or the hv_sock driver needs to
>> understand the VMBus packet format and parse the packets directly.
>> 
>> Signed-off-by: Dexuan Cui <decui@microsoft.com>
>> Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>
>> ---
>> net/vmw_vsock/hyperv_transport.c | 16 +++++++++++++---
>> 1 file changed, 13 insertions(+), 3 deletions(-)
>> 
>> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>> index 31342ab502b4..64f1290a9ae7 100644
>> --- a/net/vmw_vsock/hyperv_transport.c
>> +++ b/net/vmw_vsock/hyperv_transport.c
>> @@ -694,15 +694,25 @@ static ssize_t hvs_stream_enqueue(struct vsock_sock *vsk, struct msghdr *msg,
>> static s64 hvs_stream_has_data(struct vsock_sock *vsk)
>> {
>> 	struct hvsock *hvs = vsk->trans;
>> +	bool need_refill = !hvs->recv_desc;
> 
> For v5 remember to fix this as Paolo suggested. Dexuan proposed a fix on his thread.

Will do. And big thanks to Dexuan for the great work.

Thanks,
Xuewei

> Stefano
> 
>> 	s64 ret;
>> 
>> 	if (hvs->recv_data_len > 0)
>> -		return 1;
>> +		return hvs->recv_data_len;
>> 
>> 	switch (hvs_channel_readable_payload(hvs->chan)) {
>> 	case 1:
>> -		ret = 1;
>> -		break;
>> +		if (!need_refill)
>> +			return -EIO;
>> +
>> +		hvs->recv_desc = hv_pkt_iter_first(hvs->chan);
>> +		if (!hvs->recv_desc)
>> +			return -ENOBUFS;
>> +
>> +		ret = hvs_update_recv_data(hvs);
>> +		if (ret)
>> +			return ret;
>> +		return hvs->recv_data_len;
>> 	case 0:
>> 		vsk->peer_shutdown |= SEND_SHUTDOWN;
>> 		ret = 0;
>> -- 
>> 2.34.1
>> 
>