[virtio-comment] [PATCH RESEND v3] virtio-net: support the RSS context

* [virtio-comment] [PATCH RESEND v3] virtio-net: support the RSS context
@ 2023-10-12  7:47 Heng Qi
  2023-10-24  3:36 ` Heng Qi
  0 siblings, 1 reply; 4+ messages in thread
From: Heng Qi @ 2023-10-12  7:47 UTC (permalink / raw)
  To: virtio-comment
  Cc: Michael S . Tsirkin, Jason Wang, Cornelia Huck, Parav Pandit,
	Xuan Zhuo, Yuri Benditovich, Satananda Burla

Commit 84a1d9c48200 ("net: ethtool: extend RXNFC API to support RSS spreading of
filter matches") adds support for RSS context as a destination for receive flow filters
(see WIP work: https://lists.oasis-open.org/archives/virtio-comment/202308/msg00194.html).

An RSS context consists of configurable parameters specified by receive-side scaling.

Some use cases:
1. When users want some data flows to be steered to specific multiple rxqs, they can set
   receive flow filter rules for these data flows to an RSS context with desired rxqs.
2. Traffic isolation. Used when users want the traffic of certain applications to occupy
   several queues without being distubed.

How to set/configure an RSS context:
Assuming no RSS context has been created before.
1. ethtool -X eth0 context new start 5 equal 8

This command creates an RSS context with an id=1 for eth0, and fills in the indirection
table with rxq indexes 5-8 circularly. The hash key and hash types reuse the default
RSS configuration.

Then, we can use 'ethtool -x eth0 context 1' to query the above configuration.

2. ethtool -X eth0 context new start 6 equal 7 \
   hkey 8f:bf:dd:11:23:58:d2:8a:00:31:d0:32:a3:b5:1f:\
   1f:e4:d1:fe:47:7f:64:42:fd:d0:61:16:b8:b0:f9:71:e8:2d:36:7f:18:dd:4d:c8:f3

This command creates an RSS context with an id=2 for eth0, and fills in the indirection
table with rxq indexes 6-7 circularly. The hash key is 8f:bf:dd:11:23:58:d2:8a:00:31:d0\
:32:a3:b5:1f:1f:e4:d1:fe:47:7f:64:42:fd:d0:61:16:b8:b0:f9:71:e8:2d:36:7f:18:dd:4d:c8:f3.
Hash types reuse the default RSS configuration.

3. ethtool -N eth0 rx-flow-hash tcp4 sdfn context 1

This command specifies the hash types for the RSS context whose id=1 on eth0.
Now this RSS context only has the hash key to reuse the default RSS configuration.

4. ethtool -N eth0 flow-type udp4 src-ip 1.1.1.1 context 1

This command configures a receive flow filter rule for eth0, and the data flow matching
this rule will continue to select the final rxq according to the RSS context configuration
with id=1.

Fixes: https://github.com/oasis-tcs/virtio-spec/issues/178
Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Signed-off-by: Parav Pandit <parav@nvidia.com>
Acked-by: Satananda Burla <sburla@marvell.com>
---
v2->v3:
  1. Add Satananda's ack tag.
  2. Add link to fix issue and optimize commit log.

v1->v2:
  1. u8 to le16 for field rss_ctx_id.
  2. Add normativation when device resetting. @Yuri Benditovich
  3. Use ctrlq cmd to query rss context capability instead of reading config space. @Parav Pandit

 device-types/net/description.tex        | 85 +++++++++++++++++++++++++
 device-types/net/device-conformance.tex |  1 +
 device-types/net/driver-conformance.tex |  1 +
 3 files changed, 87 insertions(+)

diff --git a/device-types/net/description.tex b/device-types/net/description.tex
index 76585b0..55cd86d 100644
--- a/device-types/net/description.tex
+++ b/device-types/net/description.tex
@@ -88,6 +88,8 @@ \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_RSS_CONTEXT(50)] Device supports multiple RSS contexts.
+
 \item[VIRTIO_NET_F_HASH_TUNNEL(51)] Device supports inner header hash for encapsulated packets.
 
 \item[VIRTIO_NET_F_VQ_NOTF_COAL(52)] Device supports virtqueue notification coalescing.
@@ -150,6 +152,7 @@ \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device
 \item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ.
 \item[VIRTIO_NET_F_VQ_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
 \item[VIRTIO_NET_F_HASH_TUNNEL] Requires VIRTIO_NET_F_CTRL_VQ along with VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT.
+\item[VIRTIO_NET_F_RSS_CONTEXT] Requires VIRTIO_NET_F_CTRL_VQ and VIRTIO_NET_F_RSS.
 \end{description}
 
 \subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits}
@@ -1606,6 +1609,88 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
 \item If the destination receive queue is being reset (See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}), the device MUST drop the packet.
 \end{itemize}
 
+\paragraph{RSS Context}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
+
+An RSS context consists of configurable parameters specified by \ref{sec:Device Types / Network Device
+/ Device Operation / Control Virtqueue / Receive-side scaling (RSS)}.
+
+The RSS configuration supported by VIRTIO_NET_F_RSS is considered the default RSS configuration.
+
+The device offers the feature VIRTIO_NET_F_RSS_CONTEXT if it supports one or multiple RSS contexts
+(excluding the default RSS configuration) and configurable parameters.
+
+\subparagraph{Querying RSS Context Capability}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context / Querying RSS Context Capability}
+
+\begin{lstlisting}
+#define VIRTNET_RSS_CTX_CTRL 8
+ #define VIRTNET_RSS_CTX_CTRL_CAP_GET  0
+ #define VIRTNET_RSS_CTX_CTRL_ADD      1
+ #define VIRTNET_RSS_CTX_CTRL_MOD      2
+ #define VIRTNET_RSS_CTX_CTRL_DEL      3
+
+struct virtnet_rss_ctx_cap {
+    le16 max_rss_contexts;
+}
+\end{lstlisting}
+
+Field \field{max_rss_contexts} specifies the maximum number of RSS contexts \ref{sec:Device Types / Network Device /
+Device Operation / Control Virtqueue / RSS Context} supported by the device.
+
+The driver queries the RSS context capability of the device by sending the command VIRTNET_RSS_CTX_CTRL_CAP_GET
+with the structure virtnet_rss_ctx_cap.
+
+For the command VIRTNET_RSS_CTX_CTRL_CAP_GET, the structure virtnet_rss_ctx_cap is write-only for the device.
+
+\subparagraph{Setting RSS Context Parameters}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context / Setting RSS Context Parameters}
+
+\begin{lstlisting}
+struct virtnet_rss_ctx_add_modify {
+    le16 rss_ctx_id;
+    le16 padding;
+    struct virtio_net_rss_config rss;
+};
+
+struct virtnet_rss_ctx_del {
+    le16 rss_ctx_id;
+};
+\end{lstlisting}
+
+RSS context parameters:
+\begin{itemize}
+\item  \field{rss_ctx_id}: ID of the specific RSS context.
+\item  \field{rss}: RSS context parameters of the specific RSS context whose id is \field{rss_ctx_id}.
+\end{itemize}
+
+\field{padding} is reserved and it is ignored by the device.
+
+If the feature VIRTIO_NET_F_RSS_CONTEXT has been negotiated, the driver can send the following
+VIRTNET_RSS_CTX_CTRL class commands:
+\begin{enumerate}
+\item VIRTNET_RSS_CTX_CTRL_ADD: use the structure virtnet_rss_ctx_add_modify to
+       add an RSS context configured as \field{rss} and id as \field{rss_ctx_id} for the device.
+\item VIRTNET_RSS_CTX_CTRL_MOD: use the structure virtnet_rss_ctx_add_modify to
+       configure parameters of the RSS context whose id is \field{rss_ctx_id} as \field{rss} for the device.
+\item VIRTNET_RSS_CTX_CTRL_DEL: use the structure virtnet_rss_ctx_del to delete
+       the RSS context whose id is \field{rss_ctx_id} for the device.
+\end{enumerate}
+
+For commands VIRTNET_RSS_CTX_CTRL_ADD and VIRTNET_RSS_CTX_CTRL_MOD, the structure virtnet_rss_ctx_add_modify is read-only for the device.
+For the command VIRTNET_RSS_CTX_CTRL_DEL, the structure virtnet_rss_ctx_del is read-only for the device.
+
+\devicenormative{\subparagraph}{RSS Context}{Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
+
+The device MUST set \field{max_rss_contexts} to at least 1 if it offers VIRTIO_NET_F_RSS_CONTEXT.
+
+Upon reset, the device MUST clear all previously configured RSS contexts.
+
+\drivernormative{\subparagraph}{RSS Context}{Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
+
+The driver MUST have negotiated the VIRTIO_NET_F_RSS_CONTEXT feature when issuing the VIRTNET_RSS_CTX_CTRL class commands.
+
+The driver MUST set \field{rss_ctx_id} to between 1 and \field{max_rss_contexts} inclusive.
+
+The driver MUST NOT send the command VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET when the device has successfully configured at least one RSS context.
+
 \paragraph{Offloads State Configuration}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration}
 
 If the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is negotiated, the driver can
diff --git a/device-types/net/device-conformance.tex b/device-types/net/device-conformance.tex
index f88f48b..f517b00 100644
--- a/device-types/net/device-conformance.tex
+++ b/device-types/net/device-conformance.tex
@@ -15,4 +15,5 @@
 \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 / Notifications Coalescing}
 \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Inner Header Hash}
+\item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
 \end{itemize}
diff --git a/device-types/net/driver-conformance.tex b/device-types/net/driver-conformance.tex
index 9d853d9..22ff5c3 100644
--- a/device-types/net/driver-conformance.tex
+++ b/device-types/net/driver-conformance.tex
@@ -15,4 +15,5 @@
 \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 / Notifications Coalescing}
 \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Inner Header Hash}
+\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
 \end{itemize}
-- 
2.19.1.6.gb485710b


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