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Date: Wed, 9 Jun 2021 20:31:27 -0700 Message-ID: Subject: Re: [External] Re: [RFC v4] virtio-vsock: add description for datagram type To: Stefano Garzarella Cc: cong.wang@bytedance.com, Xiongchun Duan , "Michael S. Tsirkin" , 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 Wed, Jun 9, 2021 at 12:17 AM Stefano Garzarella wrote: > > On Tue, Jun 08, 2021 at 09:22:26PM -0700, Jiang Wang . wrote: > >On Tue, Jun 8, 2021 at 6:46 AM Stefano Garzarella wrote: > >> > >> On Fri, May 28, 2021 at 04:01:18AM +0000, Jiang Wang wrote: > >> >From: "jiang.wang" > >> > > >> >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 > >> >--- > >> > > >> >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. > >> > > >> > virtio-vsock.tex | 155 ++++++++++++++++++++++++++++++++++++++++++++++++++----- > >> > 1 file changed, 142 insertions(+), 13 deletions(-) > >> > > >> >diff --git a/virtio-vsock.tex b/virtio-vsock.tex > >> >index da7e641..bacac3c 100644 > >> >--- a/virtio-vsock.tex > >> >+++ b/virtio-vsock.tex > >> >@@ -9,14 +9,41 @@ \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 > >> > >> Is there a particular reason to always have the event queue as the last > >> one? > >> > >> Maybe it's better to add the datagram queues at the bottom, so the first > >> 3 queues are always the same. > >> > >I am not sure. I think Linux kernel should be fine with what you described. > >But I am not sure about QEMU. From the code, I see virtqueue is allocated > >as an array, like following, > > > >+ #ifdef CONFIG_VHOST_VSOCK_DGRAM > >+ struct vhost_virtqueue vhost_vqs[4]; > >+ #else > > struct vhost_virtqueue vhost_vqs[2]; > >+ #endi > > I see, also vhost_dev_init() requires an array, so I agree that this is > the best approach, sorry for the noise. > > Just to be sure to check that anything is working if > CONFIG_VHOST_VSOCK_DGRAM is defined, but the guest has an old driver > that doesn't support DGRAM, and viceversa. Sure. I just want to mention that the QEMU should be consistent with the device (host). If QEMU enabled CONFIG_VHOST_VSOCK_DGRAM, the device also needs to enable a similar option. Than the driver can be old or new versions. > > > >so I assume the virtqueues for tx/rx should be > >continuous? I can try to put the new queues at the end and see if it > >works or not. > > > >btw, my qemu change is here: > >https://github.com/Jiang1155/qemu/commit/6307aa7a0c347905a31f3ca6577923e2f6dd9d84 > > > >> >+\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} > >> >+ > >> >+\begin{description} > >> >+\item[VIRTIO_VSOCK_F_MRG_RXBUF (3)] Driver can merge receive buffers. > >> >+\end{description} > >> >+ > >> >+If no feature bits are defined, then assume only VIRTIO_VSOCK_F_STREAM > >> >is set. > >> > >> I'd say more like socket streams are supported, without reference to the > >> feature bit, something like: "If no feature bits are defined, then > >> assume device only supports stream socket type." > >> > >OK. > > > >> > > >> > \subsection{Device configuration layout}\label{sec:Device Types / Socket Device / Device configuration layout} > >> > > >> >@@ -64,6 +91,8 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op > >> > > >> > Packets transmitted or received contain a header before the payload: > >> > > >> >+If feature VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, use the following header. > >> >+ > >> > \begin{lstlisting} > >> > struct virtio_vsock_hdr { > >> > le64 src_cid; > >> >@@ -79,6 +108,15 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op > >> > }; > >> > \end{lstlisting} > >> > > >> >+If feature VIRTIO_VSOCK_F_MRG_RXBUF is negotiated, use the following header. > >> >+\begin{lstlisting} > >> >+struct virtio_vsock_hdr_mrg_rxbuf { > >> >+ struct virtio_vsock_hdr hdr; > >> >+ le16 num_buffers; > >> >+}; > >> >+\end{lstlisting} > >> >+ > >> >+ > >> > The upper 32 bits of src_cid and dst_cid are reserved and zeroed. > >> > > >> > Most packets simply transfer data but control packets are also used for > >> >@@ -107,6 +145,9 @@ \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 +181,15 @@ \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. > >> > >> When Arseny's change will merged, we can define and use > >> VIRTIO_VSOCK_TYPE_DGRAM,. > > > >Sure. > >> > > >> > 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 +206,7 @@ \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. > >> >@@ -170,24 +214,55 @@ \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: tx side and rx side. For the tx side, if the > >> > >> Maybe better to use sender and receiver, since we use tx and rx to > >> identify the queues. > > > >OK. > > > >> >+virtqueue is full, the packet will be dropped. > >> >+For the rx side, dgram also uses the \field{buf_alloc}. If it is full, the packet > >> >+is dropped by the receiver. > >> > >> This sentence is a bit unclear. > >> `buf_alloc` for stream socket is used to inform the other peer about the > >> receive buffer space. In this case we are using the local information, > >> so there is no need to refer to `buf_alloc`. We can write something > >> like: "The packet is dropped by the receiver if there is no space in the > >> receive buffer". > > > >OK. > > > >> >+ > >> >+\drivernormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Setting Up Receive Buffers} > >> >+\begin{itemize} > >> >+\item If VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, the driver SHOULD populate the receive queue(s) > >> >+ with buffers of at least 1526 bytes for stream sockets and 4096 > >> >bytes for datagram sockets. > >> > >> Where does 1526 come from? > > > >No specific reason. Any recommendations? > > > >> We're adding a requirement for socket streams that wasn't there until > >> now. > > > >This is only when mergeable rxbuf bit is used. I think before this, the stream > >rx buf should be at least bigger than the pkt header. We just did not put that > >into the spec. > > Mmm, I'm confused now. The statement says "If VIRTIO_VSOCK_F_MRG_RXBUF > is not negotiated" > ^ My bad. You are right, this is a new requirement for stream sockets. Not a typo. Maybe remove the part for stream sockets? Something like following: If VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, the driver SHOULD populate the receive queue(s) with buffers of at least 4096 bytes for datagram sockets. > Is it a typo? > > > IIUC when VIRTIO_VSOCK_F_MRG_RXBUF is negotiated the minimum buffer size > is virtio_vsock_hdr_mgr_rxbuf... > > > > >> >+\item If VIRTIO_VSOCK_F_MRG_RXBUF is negotiated, each buffer MUST be at > >> >+least the size of the struct virtio_vsock_hdr_mgr_rxbuf. > > ... from this ^ statement. > > And I agree that rx buf should be at least the virtio_vsock_hdr size. > > >> >+\end{itemize} > >> >+ > >> >+\begin{note} > >> >+Obviously each buffer can be split across multiple descriptor > >> >elements. > >> >+\end{note} > >> >+ > >> >+\devicenormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Setting Up Receive Buffers} > >> >+The device MUST set \field{num_buffers} to the number of descriptors used when > >> >+transmitting the packet. > >> >+ > >> >+The device MUST use only a single descriptor if VIRTIO_VSOCK_F_MRG_RXBUF > >> >+is not negotiated. > >> >+ > >> > \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: > >> > > >> >+If VIRTIO_VSOCK_F_MRG_RXBUF was not negotiated, use the following. > >> > >> Please use present as in the rest of the document, > > > >Sure. I see both past tense and present tense in the spec, so I was a > >little bit confused. > > Sorry about that. I generally always saw the present tense and seemed to > use it everywhere. > Sure. No problem. > >> > \begin{lstlisting} > >> > struct virtio_vsock_packet { > >> > struct virtio_vsock_hdr hdr; > >> >@@ -195,24 +270,70 @@ \subsubsection{Receive and Transmit}\label{sec:Device Types / Socket Device / De > >> > }; > >> > \end{lstlisting} > >> > > >> >+Otherwise, use the following form: > >> > >> Maybe better to repeat: > >> > >> If VIRTIO_VSOCK_F_MRG_RXBUF is negotiated... > >> > >OK. > > > >> >+\begin{lstlisting} > >> >+struct virtio_vsock_packet_mrg_rxbuf { > >> >+ struct virtio_vsock_hdr_mrg_rxbuf hdr; > >> >+ u8 data[]; > >> >+}; > >> >+\end{lstlisting} > >> >+ > >> >+ > >> > Virtqueue buffers for outgoing packets are read-only. Virtqueue buffers for > >> > incoming packets are write-only. > >> > > >> >+When transmitting packets to the device, \field{num_buffers} is not > >> >used. > >> >+ > >> >+\begin{enumerate} > >> >+\item \field{num_buffers} indicates how many descriptors > >> >+ this packet is spread over (including this one). > >> >+ This is valid only if VIRTIO_VSOCK_F_MRG_RXBUF was negotiated. > >> >+ This allows receipt of large packets without having to allocate large > >> >+ buffers: a packet that does not fit in a single buffer can flow > >> >+ over to the next buffer, and so on. In this case, there will be > >> >+ at least \field{num_buffers} used buffers in the virtqueue, and the device > >> >+ chains them together to form a single packet in a way similar to > >> >+ how it would store it in a single buffer spread over multiple > >> >+ descriptors. > >> >+ The other buffers will not begin with a struct virtio_vsock_hdr. > >> >+ > >> >+ If VIRTIO_VSOCK_F_MRG_RXBUF was not negotiated, then only one > >> >+ descriptor is used. > >> >+ > >> >+\item If > >> >+ \field{num_buffers} is one, then the entire packet will be > >> >+ contained within this buffer, immediately following the struct > >> >+ virtio_vsock_hdr. > >> >+\end{enumerate} > >> >+ > >> > \drivernormative{\paragraph}{Device Operation: Receive and > >> > Transmit}{Device Types / Socket Device / Device Operation / Receive > >> > and Transmit} > >> > > >> > The \field{guest_cid} configuration field MUST be used as the source CID when > >> > sending outgoing packets. > >> > > >> >-A VIRTIO_VSOCK_OP_RST reply MUST be sent if a packet is received with an > >> >+For stream and datagram sockets, A VIRTIO_VSOCK_OP_RST reply MUST be > >> > >> Perhaps we can leave it as it was before, since the `type` field > >> identifies the socket type itself. > > > >OK. > > > >> >sent if a packet is received with an > >> > unknown \field{type} value. > >> > > >> > \devicenormative{\paragraph}{Device Operation: Receive and Transmit}{Device Types / Socket Device / Device Operation / Receive and Transmit} > >> > > >> > The \field{guest_cid} configuration field MUST NOT contain a reserved CID as listed in \ref{sec:Device Types / Socket Device / Device configuration layout}. > >> > > >> >-A VIRTIO_VSOCK_OP_RST reply MUST be sent if a packet is received with an > >> >+For stream and datagram sockets, A VIRTIO_VSOCK_OP_RST reply MUST > >> >be sent if a packet is received with an > >> > unknown \field{type} value. > >> > >> Ditto. > > > >OK. > > > >> > > >> >+If VIRTIO_VSOCK_F_MRG_RXBUF has been negotiated, the device MUST set > >> >+\field{num_buffers} to indicate the number of buffers > >> >+the packet (including the header) is spread over. > >> >+ > >> >+If a receive packet is spread over multiple buffers, the device > >> >+MUST use all buffers but the last (i.e. the first $\field{num_buffers} - > >> >+1$ buffers) completely up to the full length of each buffer > >> >+supplied by the driver. > >> >+ > >> >+The device MUST use all buffers used by a single receive > >> >+packet together, such that at least \field{num_buffers} are > >> >+observed by driver as used. > >> >+ > >> > \subsubsection{Stream Sockets}\label{sec:Device Types / Socket > >> > Device / Device Operation / Stream Sockets} > >> > > >> > Connections are established by sending a VIRTIO_VSOCK_OP_REQUEST packet. If a > >> >@@ -240,6 +361,14 @@ \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 > >> > > >> > >> I don't know if maybe it's better to break this patch in two, one > >> where > >> we add datagram and one for mergeable buffer. > >> > >> But let's see what others think. > > > >OK. I can definitely break it to two patches if necessary. Thanks for > >all the comments. > > Thanks, > Stefano > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-1895-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 65019986621 for ; Thu, 10 Jun 2021 03:31:41 +0000 (UTC) MIME-Version: 1.0 References: <20210528040118.3253836-1-jiang.wang@bytedance.com> <20210608134601.5qs46xdn7bzaob77@steredhat> <20210609071725.627yqnmkzadwpubp@steredhat> In-Reply-To: <20210609071725.627yqnmkzadwpubp@steredhat> From: "Jiang Wang ." Date: Wed, 9 Jun 2021 20:31:27 -0700 Message-ID: Subject: [virtio-comment] Re: [External] Re: [RFC v4] virtio-vsock: add description for datagram type Content-Type: text/plain; charset="UTF-8" To: Stefano Garzarella Cc: "Michael S. Tsirkin" , cohuck@redhat.com, virtio-comment@lists.oasis-open.org, virtualization@lists.linux-foundation.org, asias@redhat.com, Stefan Hajnoczi , Arseny Krasnov , cong.wang@bytedance.com, Xiongchun Duan , Yongji Xie , =?UTF-8?B?5p+056iz?= , Jorgen Hansen List-ID: On Wed, Jun 9, 2021 at 12:17 AM Stefano Garzarella wrote: > > On Tue, Jun 08, 2021 at 09:22:26PM -0700, Jiang Wang . wrote: > >On Tue, Jun 8, 2021 at 6:46 AM Stefano Garzarella wrote: > >> > >> On Fri, May 28, 2021 at 04:01:18AM +0000, Jiang Wang wrote: > >> >From: "jiang.wang" > >> > > >> >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 > >> >--- > >> > > >> >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. > >> > > >> > virtio-vsock.tex | 155 ++++++++++++++++++++++++++++++++++++++++++++++++++----- > >> > 1 file changed, 142 insertions(+), 13 deletions(-) > >> > > >> >diff --git a/virtio-vsock.tex b/virtio-vsock.tex > >> >index da7e641..bacac3c 100644 > >> >--- a/virtio-vsock.tex > >> >+++ b/virtio-vsock.tex > >> >@@ -9,14 +9,41 @@ \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 > >> > >> Is there a particular reason to always have the event queue as the last > >> one? > >> > >> Maybe it's better to add the datagram queues at the bottom, so the first > >> 3 queues are always the same. > >> > >I am not sure. I think Linux kernel should be fine with what you described. > >But I am not sure about QEMU. From the code, I see virtqueue is allocated > >as an array, like following, > > > >+ #ifdef CONFIG_VHOST_VSOCK_DGRAM > >+ struct vhost_virtqueue vhost_vqs[4]; > >+ #else > > struct vhost_virtqueue vhost_vqs[2]; > >+ #endi > > I see, also vhost_dev_init() requires an array, so I agree that this is > the best approach, sorry for the noise. > > Just to be sure to check that anything is working if > CONFIG_VHOST_VSOCK_DGRAM is defined, but the guest has an old driver > that doesn't support DGRAM, and viceversa. Sure. I just want to mention that the QEMU should be consistent with the device (host). If QEMU enabled CONFIG_VHOST_VSOCK_DGRAM, the device also needs to enable a similar option. Than the driver can be old or new versions. > > > >so I assume the virtqueues for tx/rx should be > >continuous? I can try to put the new queues at the end and see if it > >works or not. > > > >btw, my qemu change is here: > >https://github.com/Jiang1155/qemu/commit/6307aa7a0c347905a31f3ca6577923e2f6dd9d84 > > > >> >+\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} > >> >+ > >> >+\begin{description} > >> >+\item[VIRTIO_VSOCK_F_MRG_RXBUF (3)] Driver can merge receive buffers. > >> >+\end{description} > >> >+ > >> >+If no feature bits are defined, then assume only VIRTIO_VSOCK_F_STREAM > >> >is set. > >> > >> I'd say more like socket streams are supported, without reference to the > >> feature bit, something like: "If no feature bits are defined, then > >> assume device only supports stream socket type." > >> > >OK. > > > >> > > >> > \subsection{Device configuration layout}\label{sec:Device Types / Socket Device / Device configuration layout} > >> > > >> >@@ -64,6 +91,8 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op > >> > > >> > Packets transmitted or received contain a header before the payload: > >> > > >> >+If feature VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, use the following header. > >> >+ > >> > \begin{lstlisting} > >> > struct virtio_vsock_hdr { > >> > le64 src_cid; > >> >@@ -79,6 +108,15 @@ \subsection{Device Operation}\label{sec:Device Types / Socket Device / Device Op > >> > }; > >> > \end{lstlisting} > >> > > >> >+If feature VIRTIO_VSOCK_F_MRG_RXBUF is negotiated, use the following header. > >> >+\begin{lstlisting} > >> >+struct virtio_vsock_hdr_mrg_rxbuf { > >> >+ struct virtio_vsock_hdr hdr; > >> >+ le16 num_buffers; > >> >+}; > >> >+\end{lstlisting} > >> >+ > >> >+ > >> > The upper 32 bits of src_cid and dst_cid are reserved and zeroed. > >> > > >> > Most packets simply transfer data but control packets are also used for > >> >@@ -107,6 +145,9 @@ \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 +181,15 @@ \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. > >> > >> When Arseny's change will merged, we can define and use > >> VIRTIO_VSOCK_TYPE_DGRAM,. > > > >Sure. > >> > > >> > 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 +206,7 @@ \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. > >> >@@ -170,24 +214,55 @@ \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: tx side and rx side. For the tx side, if the > >> > >> Maybe better to use sender and receiver, since we use tx and rx to > >> identify the queues. > > > >OK. > > > >> >+virtqueue is full, the packet will be dropped. > >> >+For the rx side, dgram also uses the \field{buf_alloc}. If it is full, the packet > >> >+is dropped by the receiver. > >> > >> This sentence is a bit unclear. > >> `buf_alloc` for stream socket is used to inform the other peer about the > >> receive buffer space. In this case we are using the local information, > >> so there is no need to refer to `buf_alloc`. We can write something > >> like: "The packet is dropped by the receiver if there is no space in the > >> receive buffer". > > > >OK. > > > >> >+ > >> >+\drivernormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Setting Up Receive Buffers} > >> >+\begin{itemize} > >> >+\item If VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, the driver SHOULD populate the receive queue(s) > >> >+ with buffers of at least 1526 bytes for stream sockets and 4096 > >> >bytes for datagram sockets. > >> > >> Where does 1526 come from? > > > >No specific reason. Any recommendations? > > > >> We're adding a requirement for socket streams that wasn't there until > >> now. > > > >This is only when mergeable rxbuf bit is used. I think before this, the stream > >rx buf should be at least bigger than the pkt header. We just did not put that > >into the spec. > > Mmm, I'm confused now. The statement says "If VIRTIO_VSOCK_F_MRG_RXBUF > is not negotiated" > ^ My bad. You are right, this is a new requirement for stream sockets. Not a typo. Maybe remove the part for stream sockets? Something like following: If VIRTIO_VSOCK_F_MRG_RXBUF is not negotiated, the driver SHOULD populate the receive queue(s) with buffers of at least 4096 bytes for datagram sockets. > Is it a typo? > > > IIUC when VIRTIO_VSOCK_F_MRG_RXBUF is negotiated the minimum buffer size > is virtio_vsock_hdr_mgr_rxbuf... > > > > >> >+\item If VIRTIO_VSOCK_F_MRG_RXBUF is negotiated, each buffer MUST be at > >> >+least the size of the struct virtio_vsock_hdr_mgr_rxbuf. > > ... from this ^ statement. > > And I agree that rx buf should be at least the virtio_vsock_hdr size. > > >> >+\end{itemize} > >> >+ > >> >+\begin{note} > >> >+Obviously each buffer can be split across multiple descriptor > >> >elements. > >> >+\end{note} > >> >+ > >> >+\devicenormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Setting Up Receive Buffers} > >> >+The device MUST set \field{num_buffers} to the number of descriptors used when > >> >+transmitting the packet. > >> >+ > >> >+The device MUST use only a single descriptor if VIRTIO_VSOCK_F_MRG_RXBUF > >> >+is not negotiated. > >> >+ > >> > \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: > >> > > >> >+If VIRTIO_VSOCK_F_MRG_RXBUF was not negotiated, use the following. > >> > >> Please use present as in the rest of the document, > > > >Sure. I see both past tense and present tense in the spec, so I was a > >little bit confused. > > Sorry about that. I generally always saw the present tense and seemed to > use it everywhere. > Sure. No problem. > >> > \begin{lstlisting} > >> > struct virtio_vsock_packet { > >> > struct virtio_vsock_hdr hdr; > >> >@@ -195,24 +270,70 @@ \subsubsection{Receive and Transmit}\label{sec:Device Types / Socket Device / De > >> > }; > >> > \end{lstlisting} > >> > > >> >+Otherwise, use the following form: > >> > >> Maybe better to repeat: > >> > >> If VIRTIO_VSOCK_F_MRG_RXBUF is negotiated... > >> > >OK. > > > >> >+\begin{lstlisting} > >> >+struct virtio_vsock_packet_mrg_rxbuf { > >> >+ struct virtio_vsock_hdr_mrg_rxbuf hdr; > >> >+ u8 data[]; > >> >+}; > >> >+\end{lstlisting} > >> >+ > >> >+ > >> > Virtqueue buffers for outgoing packets are read-only. Virtqueue buffers for > >> > incoming packets are write-only. > >> > > >> >+When transmitting packets to the device, \field{num_buffers} is not > >> >used. > >> >+ > >> >+\begin{enumerate} > >> >+\item \field{num_buffers} indicates how many descriptors > >> >+ this packet is spread over (including this one). > >> >+ This is valid only if VIRTIO_VSOCK_F_MRG_RXBUF was negotiated. > >> >+ This allows receipt of large packets without having to allocate large > >> >+ buffers: a packet that does not fit in a single buffer can flow > >> >+ over to the next buffer, and so on. In this case, there will be > >> >+ at least \field{num_buffers} used buffers in the virtqueue, and the device > >> >+ chains them together to form a single packet in a way similar to > >> >+ how it would store it in a single buffer spread over multiple > >> >+ descriptors. > >> >+ The other buffers will not begin with a struct virtio_vsock_hdr. > >> >+ > >> >+ If VIRTIO_VSOCK_F_MRG_RXBUF was not negotiated, then only one > >> >+ descriptor is used. > >> >+ > >> >+\item If > >> >+ \field{num_buffers} is one, then the entire packet will be > >> >+ contained within this buffer, immediately following the struct > >> >+ virtio_vsock_hdr. > >> >+\end{enumerate} > >> >+ > >> > \drivernormative{\paragraph}{Device Operation: Receive and > >> > Transmit}{Device Types / Socket Device / Device Operation / Receive > >> > and Transmit} > >> > > >> > The \field{guest_cid} configuration field MUST be used as the source CID when > >> > sending outgoing packets. > >> > > >> >-A VIRTIO_VSOCK_OP_RST reply MUST be sent if a packet is received with an > >> >+For stream and datagram sockets, A VIRTIO_VSOCK_OP_RST reply MUST be > >> > >> Perhaps we can leave it as it was before, since the `type` field > >> identifies the socket type itself. > > > >OK. > > > >> >sent if a packet is received with an > >> > unknown \field{type} value. > >> > > >> > \devicenormative{\paragraph}{Device Operation: Receive and Transmit}{Device Types / Socket Device / Device Operation / Receive and Transmit} > >> > > >> > The \field{guest_cid} configuration field MUST NOT contain a reserved CID as listed in \ref{sec:Device Types / Socket Device / Device configuration layout}. > >> > > >> >-A VIRTIO_VSOCK_OP_RST reply MUST be sent if a packet is received with an > >> >+For stream and datagram sockets, A VIRTIO_VSOCK_OP_RST reply MUST > >> >be sent if a packet is received with an > >> > unknown \field{type} value. > >> > >> Ditto. > > > >OK. > > > >> > > >> >+If VIRTIO_VSOCK_F_MRG_RXBUF has been negotiated, the device MUST set > >> >+\field{num_buffers} to indicate the number of buffers > >> >+the packet (including the header) is spread over. > >> >+ > >> >+If a receive packet is spread over multiple buffers, the device > >> >+MUST use all buffers but the last (i.e. the first $\field{num_buffers} - > >> >+1$ buffers) completely up to the full length of each buffer > >> >+supplied by the driver. > >> >+ > >> >+The device MUST use all buffers used by a single receive > >> >+packet together, such that at least \field{num_buffers} are > >> >+observed by driver as used. > >> >+ > >> > \subsubsection{Stream Sockets}\label{sec:Device Types / Socket > >> > Device / Device Operation / Stream Sockets} > >> > > >> > Connections are established by sending a VIRTIO_VSOCK_OP_REQUEST packet. If a > >> >@@ -240,6 +361,14 @@ \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 > >> > > >> > >> I don't know if maybe it's better to break this patch in two, one > >> where > >> we add datagram and one for mergeable buffer. > >> > >> But let's see what others think. > > > >OK. I can definitely break it to two patches if necessary. Thanks for > >all the comments. > > Thanks, > Stefano > 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. 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