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Tsirkin" To: "Jiang Wang ." Subject: Re: [External] Re: [virtio-comment] [PATCH v5] virtio-vsock: add description for datagram type Message-ID: <20210903035741-mutt-send-email-mst@kernel.org> References: <20210610181203.979686-1-jiang.wang@bytedance.com> <20210831211205-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Cong Wang , Xiongchun Duan , cohuck@redhat.com, virtualization@lists.linux-foundation.org, Yongji Xie , =?utf-8?B?5p+056iz?= , Stefan Hajnoczi , virtio-comment@lists.oasis-open.org, asias@redhat.com, Arseny Krasnov , Jorgen Hansen X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Tue, Aug 31, 2021 at 06:24:34PM -0700, Jiang Wang . wrote: > On Tue, Aug 31, 2021 at 6:13 PM Michael S. Tsirkin wrote: > > > > On Thu, Jun 10, 2021 at 06:12:03PM +0000, Jiang Wang wrote: > > > Add supports for datagram type for virtio-vsock. Datagram > > > sockets are connectionless and unreliable. To avoid contention > > > with stream and other sockets, add two more virtqueues and > > > a new feature bit to identify if those two new queues exist or not. > > > > > > Also add descriptions for resource management of datagram, which > > > does not use the existing credit update mechanism associated with > > > stream sockets. > > > > > > Signed-off-by: Jiang Wang > > > > Is this going anywhere? Linux with this included was just released but > > if no one has the cycles to work on the spec then it's not too late to > > disable the guest code in a stable@ patch. > > > > Hi Michael, > > I am still working on this (fixing the migration issue), but would > like to know if there are any more > comments or not. I did not notice any commits related to vsock > dgram merged to Linux kernel, could you show me the commit link? > > Thanks and regards, > > Jiang My bad I was thinking of seqpacket. I see that description was not posted as well, so all is well. > > > --- > > > > > > V2: addressed the comments for the previous version. > > > V3: add description for the mergeable receive buffer. > > > V4: add a feature bit for stream and reserver a bit for seqpacket. > > > Fix mrg_rxbuf related sentences. > > > V5: removed mergeable rx buffer part. It will go to a > > > separate patch. Fixed comments about tx, rx, feature bit etc. > > > > > > virtio-vsock.tex | 71 +++++++++++++++++++++++++++++++++++++++++++++++--------- > > > 1 file changed, 60 insertions(+), 11 deletions(-) > > > > > > diff --git a/virtio-vsock.tex b/virtio-vsock.tex > > > index da7e641..26a62ac 100644 > > > --- a/virtio-vsock.tex > > > +++ b/virtio-vsock.tex > > > @@ -9,14 +9,37 @@ \subsection{Device ID}\label{sec:Device Types / Socket Device / Device ID} > > > > > > \subsection{Virtqueues}\label{sec:Device Types / Socket Device / Virtqueues} > > > \begin{description} > > > -\item[0] rx > > > -\item[1] tx > > > +\item[0] stream rx > > > +\item[1] stream tx > > > +\item[2] datagram rx > > > +\item[3] datagram tx > > > +\item[4] event > > > +\end{description} > > > +The virtio socket device uses 5 queues if feature bit VIRTIO_VSOCK_F_DRGAM is set. Otherwise, it > > > +only uses 3 queues, as the following. > > > + > > > +\begin{description} > > > +\item[0] stream rx > > > +\item[1] stream tx > > > \item[2] event > > > \end{description} > > > > > > +When behavior differs between stream and datagram rx/tx virtqueues > > > +their full names are used. Common behavior is simply described in > > > +terms of rx/tx virtqueues and applies to both stream and datagram > > > +virtqueues. > > > + > > > \subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits} > > > > > > -There are currently no feature bits defined for this device. > > > +\begin{description} > > > +\item[VIRTIO_VSOCK_F_STREAM (0)] Device has support for stream socket type. > > > +\end{description} > > > + > > > +\begin{description} > > > +\item[VIRTIO_VSOCK_F_DGRAM (2)] Device has support for datagram socket type. > > > +\end{description} > > > + > > > +If no feature bits are defined, assume device only supports stream socket type. > > > > > > \subsection{Device configuration layout}\label{sec:Device Types / Socket Device / Device configuration layout} > > > > > > @@ -107,6 +130,9 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op > > > > > > \subsubsection{Virtqueue Flow Control}\label{sec:Device Types / Socket Device / Device Operation / Virtqueue Flow Control} > > > > > > +Flow control applies to stream sockets; datagram sockets do not have > > > +flow control. > > > + > > > The tx virtqueue carries packets initiated by applications and replies to > > > received packets. The rx virtqueue carries packets initiated by the device and > > > replies to previously transmitted packets. > > > @@ -140,12 +166,15 @@ \subsubsection{Addressing}\label{sec:Device Types / Socket Device / Device Opera > > > consists of a (cid, port number) tuple. The header fields used for this are > > > \field{src_cid}, \field{src_port}, \field{dst_cid}, and \field{dst_port}. > > > > > > -Currently only stream sockets are supported. \field{type} is 1 for stream > > > -socket types. > > > +Currently stream and datagram (dgram) sockets are supported. \field{type} is 1 for stream > > > +socket types. \field{type} is 3 for dgram socket types. > > > > > > Stream sockets provide in-order, guaranteed, connection-oriented delivery > > > without message boundaries. > > > > > > +Datagram sockets provide unordered, unreliable, connectionless messages > > > +with message boundaries and a maximum length. > > > + > > > \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / Device Operation / Buffer Space Management} > > > \field{buf_alloc} and \field{fwd_cnt} are used for buffer space management of > > > stream sockets. The guest and the device publish how much buffer space is > > > @@ -162,7 +191,7 @@ \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / > > > u32 peer_free = peer_buf_alloc - (tx_cnt - peer_fwd_cnt); > > > \end{lstlisting} > > > > > > -If there is insufficient buffer space, the sender waits until virtqueue buffers > > > +For stream sockets, if there is insufficient buffer space, the sender waits until virtqueue buffers > > > are returned and checks \field{buf_alloc} and \field{fwd_cnt} again. Sending > > > the VIRTIO_VSOCK_OP_CREDIT_REQUEST packet queries how much buffer space is > > > available. The reply to this query is a VIRTIO_VSOCK_OP_CREDIT_UPDATE packet. > > > @@ -170,22 +199,33 @@ \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / > > > previously receiving a VIRTIO_VSOCK_OP_CREDIT_REQUEST packet. This allows > > > communicating updates any time a change in buffer space occurs. > > > > > > +Unlike stream sockets, dgram sockets do not use VIRTIO_VSOCK_OP_CREDIT_UPDATE or > > > +VIRTIO_VSOCK_OP_CREDIT_REQUEST packets. The dgram buffer management > > > +is split to two parts: sender side and receiver side. For the sender side, if the > > > +virtqueue is full, the packet will be dropped. > > > +For the receiver side, the packet is dropped by the receiver if there is no space in the > > > +receive buffer. > > > + > > > \drivernormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Buffer Space Management} > > > -VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > -sufficient free buffer space for the payload. > > > +For stream sockets, VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > +sufficient free buffer space for the payload. For dgram sockets, VIRTIO_VSOCK_OP_RW data packets > > > +MAY be transmitted when the peer rx buffer is full. Then the packet will be dropped by the peer, > > > +and driver will not get any notification. > > > > > > All packets associated with a stream flow MUST contain valid information in > > > \field{buf_alloc} and \field{fwd_cnt} fields. > > > > > > \devicenormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Buffer Space Management} > > > -VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > -sufficient free buffer space for the payload. > > > +For stream sockets, VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > +sufficient free buffer space for the payload. For dgram sockets, VIRTIO_VSOCK_OP_RW data packets > > > +MAY be transmitted when the peer rx buffer is full. Then the packet will be dropped by the peer, > > > +and the device will not get any notification. > > > > > > All packets associated with a stream flow MUST contain valid information in > > > \field{buf_alloc} and \field{fwd_cnt} fields. > > > > > > \subsubsection{Receive and Transmit}\label{sec:Device Types / Socket Device / Device Operation / Receive and Transmit} > > > -The driver queues outgoing packets on the tx virtqueue and incoming packet > > > +The driver queues outgoing packets on the tx virtqueue and allocates incoming packet > > > receive buffers on the rx virtqueue. Packets are of the following form: > > > > > > \begin{lstlisting} > > > @@ -195,6 +235,7 @@ \subsubsection{Receive and Transmit}\label{sec:Device Types / Socket Device / De > > > }; > > > \end{lstlisting} > > > > > > + > > > Virtqueue buffers for outgoing packets are read-only. Virtqueue buffers for > > > incoming packets are write-only. > > > > > > @@ -240,6 +281,14 @@ \subsubsection{Stream Sockets}\label{sec:Device Types / Socket Device / Device O > > > destination) address tuple for a new connection while the other peer is still > > > processing the old connection. > > > > > > +\subsubsection{Datagram Sockets}\label{sec:Device Types / Socket Device / Device Operation / Datagram Sockets} > > > + > > > +Datagram (dgram) sockets are connectionless and unreliable. The sender just sends > > > +a message to the peer and hopes it will be delivered. A VIRTIO_VSOCK_OP_RST reply is sent if > > > +a receiving socket does not exist on the destination. > > > +If the transmission or receiving buffers are full, the packets > > > +are dropped. > > > + > > > \subsubsection{Device Events}\label{sec:Device Types / Socket Device / Device Operation / Device Events} > > > > > > Certain events are communicated by the device to the driver using the event > > > -- > > > 2.11.0 > > > > > > > > > This publicly archived list offers a means to provide input to the > > > OASIS Virtual I/O Device (VIRTIO) TC. > > > > > > In order to verify user consent to the Feedback License terms and > > > to minimize spam in the list archive, subscription is required > > > before posting. > > > > > > Subscribe: virtio-comment-subscribe@lists.oasis-open.org > > > Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org > > > List help: virtio-comment-help@lists.oasis-open.org > > > List archive: https://lists.oasis-open.org/archives/virtio-comment/ > > > Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf > > > List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists > > > Committee: https://www.oasis-open.org/committees/virtio/ > > > Join OASIS: https://www.oasis-open.org/join/ > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization