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Subject: Re: [PATCH v11] virtio-net: support device stats
On Wed, Mar 09, 2022 at 04:25:26PM +0800, Xuan Zhuo wrote: > On Mon, 7 Mar 2022 15:58:03 +0800, Jason Wang <jasowang@redhat.com> wrote: > > > > å 2022/3/2 äå4:52, Xuan Zhuo åé: > > > This patch allows the driver to obtain some statistics from the device. > > > > > > In the back-end implementation, we can count a lot of such information, > > > which can be used for debugging and judging the running status of the > > > back-end. We hope to directly display it to the user through ethtool. > > > > > > To get stats atomically, try to get stats for all queue pairs in one > > > command. > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > > > Suggested-by: Michael S. Tsirkin <mst@redhat.com> > > > --- > > > v11: > > > 1. Use michael's advice to introduce virtio_net_ctrl_queue_stats to get vq stats > > > based on vq num and type > > > 2. split stats structure > > > > > > v10: > > > 1. use description/item for the item of the queue pair > > > 2. use one command to get the stats of all queue pairs > > > > > > v8: > > > 1. Modified based on comments by Cornelia Huck > > > > > > v7: > > > 1. add rx_reset, tx_reset > > > 2. add device normative and dirver normative > > > 3. add comments for *_packets, *_bytres > > > > > > v6: > > > 1. correct the names and descriptions of some stats items > > > > > > v5: > > > 1. add VIRTIO_NET_CTRL_STATS_GET_CTRL_VQ > > > 2. more item for virtio_net_ctrl_reply_stats_queue_pair > > > > > > v4: > > > 1. remove dev_stats_num, {rx|tx}_stats_num > > > 2. Use two commands to get the stats of queue pair and dev respectively > > > > > > v3 changes: > > > 1. add dev_version > > > 2. use queue_pair_index replace rx_num, tx_num > > > 3. Explain the processing when the device and driver support different numbers > > > of stats > > > > > > conformance.tex | 2 + > > > content.tex | 391 +++++++++++++++++++++++++++++++++++++++++++++++- > > > 2 files changed, 390 insertions(+), 3 deletions(-) > > > > > > diff --git a/conformance.tex b/conformance.tex > > > index 42f8537..c67f877 100644 > > > --- a/conformance.tex > > > +++ b/conformance.tex > > > @@ -142,6 +142,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode} > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration / Setting Offloads State} > > > \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) } > > > +\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats} > > > \end{itemize} > > > > > > \conformance{\subsection}{Block Driver Conformance}\label{sec:Conformance / Driver Conformance / Block Driver Conformance} > > > @@ -401,6 +402,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Gratuitous Packet Sending} > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Automatic receive steering in multiqueue mode} > > > \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS processing} > > > +\item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats} > > > \end{itemize} > > > > > > \conformance{\subsection}{Block Device Conformance}\label{sec:Conformance / Device Conformance / Block Device Conformance} > > > diff --git a/content.tex b/content.tex > > > index c6f116c..5746f49 100644 > > > --- a/content.tex > > > +++ b/content.tex > > > @@ -3092,6 +3092,9 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits > > > \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control > > > channel. > > > > > > +\item[VIRTIO_NET_F_CTRL_STATS(55)] Device can provide device-level statistics > > > + to the driver through the control channel. > > > + > > > \item[VIRTIO_NET_F_HOST_USO (56)] Device can receive USO packets. Unlike UFO > > > (fragmenting the packet) the USO splits large UDP packet > > > to several segments when each of these smaller packets has UDP header. > > > @@ -3137,6 +3140,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device > > > \item[VIRTIO_NET_F_GUEST_ANNOUNCE] Requires VIRTIO_NET_F_CTRL_VQ. > > > \item[VIRTIO_NET_F_MQ] Requires VIRTIO_NET_F_CTRL_VQ. > > > \item[VIRTIO_NET_F_CTRL_MAC_ADDR] Requires VIRTIO_NET_F_CTRL_VQ. > > > +\item[VIRTIO_NET_F_CTRL_STATS] Requires VIRTIO_NET_F_CTRL_VQ. > > > \item[VIRTIO_NET_F_RSC_EXT] Requires VIRTIO_NET_F_HOST_TSO4 or VIRTIO_NET_F_HOST_TSO6. > > > \item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ. > > > \end{description} > > > @@ -4015,6 +4019,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > > > u8 command; > > > u8 command-specific-data[]; > > > u8 ack; > > > + u8 command-specific-data-reply[]; > > > }; > > > > > > /* ack values */ > > > @@ -4023,9 +4028,11 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > > > \end{lstlisting} > > > > > > The \field{class}, \field{command} and command-specific-data are set by the > > > -driver, and the device sets the \field{ack} byte. There is little it can > > > -do except issue a diagnostic if \field{ack} is not > > > -VIRTIO_NET_OK. > > > +driver, and the device sets the \field{ack} byte and optionally > > > +\field{command-specific-data-reply}. There is little the driver can > > > +do except issue a diagnostic if \field{ack} is not VIRTIO_NET_OK. > > > + > > > +The command VIRTIO_NET_CTRL_STATS_GET contains \field{command-specific-data-reply}. > > > > > > \paragraph{Packet Receive Filtering}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Packet Receive Filtering} > > > \label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Setting Promiscuous Mode}%old label for latexdiff > > > @@ -4471,6 +4478,384 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi > > > according to the native endian of the guest rather than > > > (necessarily when not using the legacy interface) little-endian. > > > > > > +\paragraph{Device Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats} > > > + > > > +If the VIRTIO_NET_F_CTRL_STATS feature is negotiated, the driver can > > > +get the device stats from the device in \field{command-specific-data-reply}. > > > + > > > +To get the stats, the following definitions are used: > > > +\begin{lstlisting} > > > +#define VIRTIO_NET_CTRL_STATS 6 > > > +#define VIRTIO_NET_CTRL_STATS_GET 0 > > > + > > > +#define VIRTIO_NET_STATS_TYPE_CVQ 0 > > > +#define VIRTIO_NET_STATS_TYPE_RX_BASIC 1 > > > +#define VIRTIO_NET_STATS_TYPE_RX_CSUM 2 > > > +#define VIRTIO_NET_STATS_TYPE_RX_GSO 3 > > > +#define VIRTIO_NET_STATS_TYPE_RX_RESET 4 > > > +#define VIRTIO_NET_STATS_TYPE_TX_BASIC 5 > > > +#define VIRTIO_NET_STATS_TYPE_TX_CSUM 6 > > > +#define VIRTIO_NET_STATS_TYPE_TX_GSO 7 > > > +#define VIRTIO_NET_STATS_TYPE_TX_RESET 8 > > > + > > > +\end{lstlisting} > > > + > > > +The following layout structures are used: > > > + > > > +\field{command-specific-data} > > > +\begin{lstlisting} > > > +struct virtio_net_ctrl_queue_stats { > > > + u16 nstats; > > > + struct { > > > + u16 queue_num; > > > + u16 type; > > > + u16 length; > > > + } stats[]; > > > +}; > > > +\end{lstlisting} > > > + > > > +\field{command-specific-data-reply} > > > +\begin{lstlisting} > > > +struct virtio_net_stats_cvq { > > > + le64 command_num; > > > + le64 ok_num; > > > +}; > > > + > > > +struct virtio_net_stats_rx_basic { > > > + le64 rx_packets; > > > + le64 rx_bytes; > > > + > > > + le64 rx_notification; > > > + le64 rx_interrupt; > > > + > > > + le64 rx_drop; > > > + le64 rx_drop_overruns; > > > +}; > > > + > > > +struct virtio_net_stats_rx_csum { > > > + le64 rx_csum_valid; > > > + le64 rx_needs_csum; > > > + le64 rx_csum_bad; > > > + le64 rx_csum_none; > > > +}; > > > + > > > +struct virtio_net_stats_rx_gso { > > > + le64 rx_gso_packets; > > > + le64 rx_gso_bytes; > > > +}; > > > + > > > +struct virtio_net_stats_rx_reset { > > > + le64 rx_reset; > > > +}; > > > + > > > +struct virtio_net_stats_tx_basic { > > > + le64 tx_packets; > > > + le64 tx_bytes; > > > + > > > + le64 tx_notification; > > > + le64 tx_interrupt; > > > + > > > + le64 tx_drop; > > > + le64 tx_drop_malformed; > > > +}; > > > + > > > +struct virtio_net_stats_tx_csum { > > > + le64 tx_csum_none; > > > + le64 tx_needs_csum; > > > +}; > > > + > > > +struct virtio_net_stats_tx_gso { > > > + le64 tx_gso_packets; > > > + le64 tx_gso_bytes; > > > +}; > > > + > > > +struct virtio_net_stats_tx_reset { > > > + le64 tx_reset; > > > +}; > > > + > > > +\end{lstlisting} > > > + > > > +Use the command VIRTIO_NET_CTRL_STATS_GET and \field{command-specific-data} > > > +containing struct virtio_net_ctrl_queue_stats to get the device stats. > > > +The result is returned by \field{command-specific-data-reply}. > > > > > > It's better to move this sentence after the description above. And we > > need explain the result a little bit more, e.g the stats ware returned > > in the order of the type specified in the virtio_net_ctrl_queue_stats. > > > > > > > + > > > +\begin{description} > > > + \item [nstats] > > > + The number of \field{stats}. > > > + > > > + \item [queue_num] > > > + The queue num of the vq to be obtained. The vq can be receiveq, > > > + transmitq or controlq. > > > > > > This could be simplified as "The number of the virtqueue to obtain the > > statistics" > > > > > > > + > > > + \item [type] > > > + The type of the stats to be obtained. > > > + > > > + \item [length] > > > + Limits the size of the memory space occupied by the returned stats. > > > > > > What's the value of having this? Or how can driver know which value > > should it use? > > > > > > > + > > > +\end{description} > > > + > > > +Correspondence between the vq type, the stats type, the stats structure and the > > > +required features. > > > +\begin{tabular}{ |l|l|l|l| } > > > + \hline > > > + VQ Type & Stats Type & Stats Structure & Features \\ \hline > > > + > > > + controlq & VIRTIO_NET_STATS_TYPE_CVQ & virtio_net_stats_cvq & \\ \hline > > > > > > I think CVQ should require CVQ feature to be negotiated. > > > > > > > + > > > + \multirow{4}*{receiveq} & VIRTIO_NET_STATS_TYPE_RX_BASIC & virtio_net_stats_rx_basic & \\ \cline{2-4} > > > + & VIRTIO_NET_STATS_TYPE_RX_CSUM & virtio_net_stats_rx_csum & VIRTIO_NET_F_GUEST_CSUM \\ \cline{2-4} > > > + & VIRTIO_NET_STATS_TYPE_RX_GSO & virtio_net_stats_rx_gso & VIRTIO_NET_F_GUEST_TSO4, TSO6, or UFO \\ \cline{2-4} > > > > > > It's better to aovid abbrev for features like TSO6. > > > > > > > + & VIRTIO_NET_STATS_TYPE_RX_RESET & virtio_net_stats_rx_reset & VIRTIO_F_RING_RESET \\ \hline > > > + > > > + \multirow{4}*{transmitq} & VIRTIO_NET_STATS_TYPE_TX_BASIC & virtio_net_stats_tx_basic & \\ \cline{2-4} > > > + & VIRTIO_NET_STATS_TYPE_TX_CSUM & virtio_net_stats_tx_csum & VIRTIO_NET_F_CSUM \\ \cline{2-4} > > > + & VIRTIO_NET_STATS_TYPE_TX_GSO & virtio_net_stats_tx_gso & VIRTIO_NET_F_HOST_TSO4, TSO6, USO or UFO \\ \cline{2-4} > > > + & VIRTIO_NET_STATS_TYPE_TX_RESET & virtio_net_stats_tx_reset & VIRTIO_F_RING_RESET \\ > > > + \hline > > > +\end{tabular} > > > + > > > + > > > +\subparagraph{Controlq Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Controlq Stats} > > > + > > > +The structure corresponding to the controlq stats is virtio_net_stats_cvq. > > > + > > > +\begin{description} > > > + \item [command_num] > > > + The number of commands, including the current command. > > > + > > > + \item [ok_num] > > > + The number of commands (including the current command) where the ack was VIRTIO_NET_OK. > > > +\end{description} > > > + > > > + > > > +\subparagraph{Receiveq Basic Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Receiveq Basic Stats} > > > + > > > +The structure corresponding to the receiveq basic stats is virtio_net_stats_rx_basic. > > > + > > > +Receiveq basic stats doesn't need any features, as long as the device supports > > > +VIRTIO_NET_F_CTRL_STATS. The following are the receiveq basic stats. > > > + > > > +\begin{description} > > > + \item [rx_packets] > > > + The number of packets received by device (not the packets passed to the > > > + guest), including the dropped packets by device. > > > + > > > + \item [rx_bytes] > > > + The number of bytes received by device (not the packets passed to the > > > + guest), including the dropped packets by device. > > > + > > > + \item [rx_notification] > > > + The number of driver notifications. > > > + > > > + \item [rx_interrupt] > > > + The number of device interrupts. > > > + > > > + \item [rx_drop] > > > + The number of packets dropped by the receiveq. Contains all kinds of > > > + packet drop. > > > + > > > + \item [rx_drop_overruns] > > > + The number of packets dropped by the receiveq when no more descriptors > > > + were available. > > > + > > > +\end{description} > > > + > > > +\subparagraph{Transmitq Basic Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Transmitq Basic Stats} > > > + > > > +The structure corresponding to the transmitq basic stats is virtio_net_stats_tx_basic. > > > + > > > +Transmitq basic stats doesn't need any features, as long as the device supports > > > +VIRTIO_NET_F_CTRL_STATS. The following are the transmitq basic stats. > > > + > > > +\begin{description} > > > + \item [tx_packets] > > > + The number of packets sent by device (not the packets received from the > > > > > > s/received/sent/? > > > > > > > + guest), excluding the dropped packets by device. > > > + > > > + \item [tx_bytes] > > > + The number of bytes sent by device (not the packets received from the > > > + guest), excluding the dropped packets by device. > > > + > > > + \item [tx_notification] > > > + The number of driver notifications. > > > + > > > + \item [tx_interrupt] > > > + The number of device interrupts. > > > + > > > + \item [tx_drop] > > > + The number of packets dropped by the transmitq. Contains all kinds of > > > + packet drop. > > > + > > > + \item [tx_drop_malformed] > > > + The number of packets dropped when the descriptor is in an error state. > > > + For example, the buffer is too short. > > > + > > > +\end{description} > > > + > > > +\subparagraph{Receiveq CSUM Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Receiveq CSUM Stats} > > > + > > > +The structure corresponding to the receiveq csum stats is virtio_net_stats_rx_csum. > > > + > > > +Only after the VIRTIO_NET_F_GUEST_CSUM negotiation is successful, the receiveq > > > +csum stats can be obtained. > > > + > > > +The following are the receiveq csum stats: > > > + > > > +\begin{description} > > > + \item [rx_csum_valid] > > > + The number of packets with VIRTIO_NET_HDR_F_DATA_VALID. > > > + > > > + \item [rx_needs_csum] > > > + The number of packets with VIRTIO_NET_HDR_F_NEEDS_CSUM. > > > + > > > + \item [rx_csum_bad] > > > + The number of packets with abnormal csum. > > > + > > > + \item [rx_csum_none] > > > + The number of packets without hardware csum. The packet here refers to > > > + the non-TCP/UDP packet that the backend cannot recognize. > > > + > > > +\end{description} > > > + > > > +\subparagraph{Transmitq CSUM Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Transmitq CSUM Stats} > > > + > > > +The structure corresponding to the transmitq csum stats is virtio_net_stats_tx_csum. > > > + > > > +Only after the VIRTIO_NET_F_CSUM negotiation is successful, the transmitq csum > > > +stats can be obtained. > > > + > > > +The following are the transmitq csum stats: > > > + > > > +\begin{description} > > > + \item [tx_csum_none] > > > + The number of packets that didn't require hardware csum. > > > + > > > + \item [tx_needs_csum] > > > + The number of packets that required hardware csum. > > > + > > > +\end{description} > > > + > > > +\subparagraph{Receiveq GSO Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Receiveq GSO Stats} > > > + > > > +The structure corresponding to the receiveq gso stats is virtio_net_stats_rx_gso. > > > + > > > +If one of the VIRTIO_NET_F_GUEST_TSO4, TSO6, or UFO options have > > > +been negotiated, the receiveq gso stats can be obtained. > > > + > > > +Rx gso packets refer to packets passed by the device to the driver where > > > +\field{gso_type} is not VIRTIO_NET_HDR_GSO_NONE. > > > + > > > +The statistics of the following receiveq gso stats are based on the rx gso > > > +packet. The device may receive multiple small packets, and finally combine them > > > +into one rx gso packet and pass it to the driver. It is also possible to receive > > > +a gso packet and pass it directly to the driver. We should count the information > > > +of the rx gso packet that is finally passed to the driver (such as number and > > > +bytes). Instead of the information of the small packet. > > > > > > If we don't want to explain why we use a single counter for those two > > cases, we probably can drop the above paragraph and simply say the > > rx_gso_packets is the number of gso packet produced by the device. > > > > Btw, we had VIRTIO_NET_GUEST_RSC{4|6}, is it better to use different > > counters? > > > RSC information doesn't seem to be very comprehensive in the spec. CC Yuri. Yuri do you feel we need to clarify things in the spec? If yes please create a github issue. Thanks! > I'm not sure, > is the gso_type of the RSC package also VIRTIO_NET_HDR_GSO_TCPV4 or VIRTIO_NET_HDR_GSO_TCPV6? > > If yes, I plan to modify gso's stats to the following form to record gso's > stats. In this case include the RSC package. > > \begin{description} > \item [rx_gso_packets] > The number of the rx gso packets. > > \item [rx_gso_bytes] > The number of bytes(excluding the virtio net header) of the rx gso packets. > > \item [rx_gso_packets_coalesced] > The number of the rx gso packages generated by merging. > > \item [rx_gso_bytes_coalesced] > The number of bytes(excluding the virtio net header) of the rx gso packets generated by merging. > > \item [rx_gso_segments] > The number of coalesced segments. > > \item [rx_gso_segments_bytes] > The number of bytes of coalesced segments. > > \end{description} > > \begin{description} > \item [tx_gso_packets] > The number of the tx gso packets. > > \item [tx_gso_bytes] > The number of bytes(excluding the virtio net header) of the tx gso packets. > > \item [tx_gso_packets_split] > The number of the tx gso packets that been split. > > \item [tx_gso_bytes_split] > The number of bytes(excluding the virtio net header) of the tx gso packets that been split. > > \item [tx_gso_segments] > The number of segments split from the gso package. > > \item [tx_gso_segments_bytes] > The number of bytes(excluding the virtio net header) of segments split from the gso package. > \end{description} > > Thanks. > > > > > > > > + > > > +\begin{description} > > > + \item [rx_gso_packets] > > > + The number of the rx gso packets. > > > + > > > + \item [rx_gso_bytes] > > > + The number of bytes(excluding the virtio net header) of the rx gso packets. > > > +\end{description} > > > + > > > +\subparagraph{Transmitq GSO Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Transmitq GSO Stats} > > > + > > > +The structure corresponding to the receiveq gso stats is virtio_net_stats_tx_gso. > > > + > > > +If one of the VIRTIO_NET_F_HOST_TSO4, TSO6, USO or UFO options have > > > +been negotiated, the transmitq gso stats can be obtained. > > > + > > > +Tx gso packets refer to packets passed by the driver to the device where > > > +\field{gso_type} is not VIRTIO_NET_HDR_GSO_NONE. > > > + > > > +The statistics of the following transmitq gso stats are based on the tx gso > > > +packet. The device may receive a tx gso packet from the driver, and then may split > > > +it into multiple small packets or send the tx gso packet directly. But the device > > > +counts the information of the gso packet received from the driver (such as the > > > +number and bytes). Instead of the packet information after splitting. > > > > > > Similar to rx gso, is it better to use two counters? > > > > > > > + > > > +\begin{description} > > > + \item [tx_gso_packets] > > > + The number of the tx gso packets. > > > + > > > + \item [tx_gso_bytes] > > > + The number of bytes(excluding the virtio net header) of the tx gso packets. > > > +\end{description} > > > + > > > +\subparagraph{Receiveq Reset Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Receiveq Reset Stats} > > > + > > > +The structure corresponding to the receiveq reset stats is virtio_net_stats_rx_reset. > > > + > > > +Only when VIRTIO_F_RING_RESET is successfully negotiated, the receiveq reset stats > > > +can be obtained. > > > + > > > +See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset} > > > +for more about \field{rx_reset}. > > > + > > > +\begin{description} > > > + \item [rx_reset] > > > + The number of queue resets. > > > +\end{description} > > > + > > > +\subparagraph{Transmitq Reset Stats}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats / Transmitq Reset Stats} > > > + > > > +The structure corresponding to the transmitq reset stats is virtio_net_stats_tx_reset. > > > + > > > +Only when VIRTIO_F_RING_RESET is successfully negotiated, the transmitq reset stats > > > +can be obtained. > > > + > > > +See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset} > > > +for more about \field{tx_reset}. > > > + > > > +\begin{description} > > > + \item [tx_reset] > > > + The number of queue resets. > > > +\end{description} > > > + > > > +\devicenormative{\subparagraph}{Device Stats}{Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats} > > > + > > > +If virtio_net_ctrl_queue_stats is incorrect (such as the following), the device > > > +MUST set \field{ack} to VIRTIO_NET_ERR. > > > +\begin{itemize} > > > + \item \field{queue_num} exceeds the queue range. > > > + \item \field{type} is not a known value. > > > > > > What happens if driver tries to query RX stats through a TX index? > > > > > > > + \item The type of vq does not match \field{type}. > > > + \item The feature corresponding to the specified \field{type} was not successfully > > > + negotiated. > > > + \item The size of \field{command-specific-data-reply} is less than the sum > > > + of \field{length}. > > > > > > I'm not sure I get here, I guess this proposal allows the driver to > > query an array of stats. So I guess it means the size of required stats > > instead of the size of \field{command-specific-data-reply}. > > > > > > > +\end{itemize} > > > + > > > +The device MUST write the requested stats structures in > > > +\field{command-specific-data-reply} in the order specified by the structure > > > +virtio_net_ctrl_queue_stats. > > > > > > Do we need per stat error code here? Or device can simply fail a batch > > of query if one of those fails? > > > > > > > + > > > +The size of each stats MUST be less than or equal to the corresponding > > > +\field{length}, but the space it occupies MUST be equal to the corresponding > > > +\field{length}. > > > > > > I wonder how the length trick can work here. Is this used for extension? > > If yes, how can driver know a suitable length? What happens if device > > support more stats? > > > > > > > + > > > +\drivernormative{\subparagraph}{Device Stats}{Device Types / Network Device / Device Operation / Control Virtqueue / Device Stats} > > > + > > > +When a driver tries to obtain a certain stats, it MUST confirm that the relevant > > > +feature negotiation is successful. > > > + > > > +\field{type} in struct virtio_net_ctrl_queue_stats MUST correspond to the vq > > > +specified by \field{queue_num}. > > > + > > > +\field{length} in struct virtio_net_ctrl_queue_stats MUST be greater than or > > > +equal to the size of the structure corresponding to \field{type}. It MUST be a > > > +multiple of 8. > > > > > > Why do we need the padding here? > > > > > > > + > > > +The size of \field{command-specific-data-reply} allocated by the driver MUST be > > > +greater than or equal to the sum of \field{legnth} in struct > > > > > > typo. > > > > > > > +virtio_net_ctrl_queue_stats. > > > > > > Any value that we can allocate more than the sum of the length? > > > > Thanks > > > > > > > + > > > +When the driver reads the response, it MUST read > > > +\field{command-specific-data-reply} one by one based on the set \field{length} > > > +and \field{type}. > > > > > > \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device > > > Types / Network Device / Legacy Interface: Framing Requirements} > > > -- > > > 2.31.0 > > > > >
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