[virtio-dev] [PATCH v3] virtio-net: support device stats

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

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.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---

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

 content.tex | 115 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)

diff --git a/content.tex b/content.tex
index 7cec1c3..2e45a55 100644
--- a/content.tex
+++ b/content.tex
@@ -2972,6 +2972,9 @@ \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.
@@ -3017,6 +3020,7 @@ \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}
@@ -3895,6 +3899,7 @@ \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 */
@@ -3906,6 +3911,9 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 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.
+\field{command-specific-data-reply} is alloced by driver, then pass to device.
+It is filled by the device. It is optional. Some commands need to get some
+information from the device.

 \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
@@ -4384,6 +4392,113 @@ \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device
 See \ref{sec:Basic
 Facilities of a Virtio Device / Virtqueues / Message Framing}.

+\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 device stats from the device by \field{command-specific-data-reply}.
+
+\subparagraph{Device stats keys}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device stats keys / Device stats keys}
+
+The keys of the device stats are defined as follows. When the device fills in
+\field{command-specific-data-reply}, it MUST be written in the following order.
+Subsequent newly added keys MUST be added at the end of each category.
+These keys will eventually be shown to the user.
+
+All stats are divided into three categories:
+
+\begin{itemize}
+    \item dev stats: the stats of the device
+        \begin{itemize}
+            \item dev_version: The number of device version.
+            \item dev_reset: The number of device reset.
+        \end{itemize}
+
+    \item rx stats: the stats of the rx queue
+        \begin{itemize}
+            \item rx[N]_inter: The number of interrupts sent by the rx queue.
+            \item rx[N]_drop: The number of packets dropped by the rx queue. Contains all kinds of packet loss.
+            \item rx[N]_drop_overruns: The number of packets dropped by the rx queue when no more avail desc.
+            \item rx[N]_csum_bad: The number of packets with abnormal csum in the rx queue.
+            \item rx[N]_gso_packets: The number of gso packets received by rx.
+            \item rx[N]_gso_bytes: The number of gso bytes received by rx.
+            \item rx[N]_oversize_pkts: The number of oversized packets received by the rx queue.
+        \end{itemize}
+
+    \item tx stats: the stats of the tx queue
+        \begin{itemize}
+            \item tx[N]_inter: The number of interrupts sent by the tx queue.
+            \item tx[N]_drop: The number of packets dropped by the tx queue. Contains all kinds of packet loss.
+            \item tx[N]_csum: The number of packets that completes csum by the device.
+            \item tx[N]_gso_packets: The number of gso packets transmitted.
+            \item tx[N]_gso_bytes: The number of gso bytes transmitted.
+        \end{itemize}
+\end{itemize}
+
+\subparagraph{Device stats get}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Device stats keys / Device stats get}
+
+To get the stats, the following definitions are used:
+\begin{lstlisting}
+#define VIRTIO_NET_CTRL_STATS        6
+#define VIRTIO_NET_CTRL_STATS_GET    0
+\end{lstlisting}
+
+The following layout structure are used:
+
+\field{command-specific-data}
+\begin{lstlisting}
+le64 queue_pair_index
+le64 dev_stats_num;
+le64 rx_stats_num;
+le64 tx_stats_num;
+\end{lstlisting}
+
+\field{command-specific-data-reply}
+\begin{lstlisting}
+le64 queue_pair_index
+le64 dev_stats_num;
+le64 rx_stats_num;
+le64 tx_stats_num;
+le64 dev_stats[dev_stats_num];
+le64 rx_stats[rx_stats_num];
+le64 tx_stats[tx_stats_num];
+\end{lstlisting}
+
+The command VIRTIO_NET_CTRL_STATS_GET is used to obtain this information.
+
+Regarding the variables in \field{command-specific-data}:
+\begin{itemize}
+    \item \field{queue_pair_index}: Specify the queue pair index of the queue that the driver wants to get stats.
+    \item \field{dev_stats_num}: Indicates the number of dev stats supported by the driver.
+    \item \field{rx_stats_num}: Indicates the number of stats information the driver wants for rx queue.
+    \item \field{tx_stats_num}: Indicates the number of stats information the driver wants for tx queue.
+\end{itemize}
+
+Regarding the variables in \field{command-specific-data-reply}:
+\begin{itemize}
+    \item All variables of \field{command-specific-data-reply} are set by the device.
+    \item \field{queue_pair_index} MUST be equal to the variable with the same name in \field{command-specific-data}.
+    \item These variables(\field{dev_stats_num}, \field{rx_stats_num}, \field{tx_stats_num}) MUST be
+            less than or equal to the variables with the same name in \field{command-specific-data}.
+            These values indicate the amount of stats actually filled in.
+    \item \field{command-specific-data-reply} is meaningful only when \field{ack} is equal to VIRTIO_NET_OK.
+\end{itemize}
+
+The variables \field{dev_stats_num}, \field{rx_stats_num}, \field{tx_stats_num} in \field{command-specific-data}
+specify which stats the driver wants to get, but in fact the device may support
+more or fewer stats.
+
+If the actual number of stats supported by the device is equal to or less than
+the number that the driver wants to obtain, then the device MUST write all the
+stats to the corresponding position of \field{command-specific-data-reply}.
+
+And if the number of stats actually supported by the device is more than the
+driver requires, then the device MUST only write the number supported by the
+driver.
+
+If the some of the variables \field{dev_stats_num}, \field{rx_stats_num}, \field{tx_stats_num} in \field{command-specific-data} are 0,
+that means that the driver does not want to obtain this type of stats,
+then the device MUST set the same name field in \field{command-specific-data-reply} to 0, and skip this type of stats.
+
 \section{Block Device}\label{sec:Device Types / Block Device}

 The virtio block device is a simple virtual block device (ie.
--
2.31.0


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