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Subject: Re: [virtio-comment] [PATCH] virtio-net: support the RSS context
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
(pls see https://lists.oasis-open. org/archives/virtio-comment/202308/msg00194.html).
An RSS context consists of configurable parameters specified by receive-side scaling.
Usecase:
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.
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 \
 Âhkey 8f:bf:dd:11:23:58:d2:8a:00:31:d0:32:a3:b5:1f:\
 Â1f: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.
Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
---
Âdevice-types/net/description.tex    | 70 +++++++++++++++++++++++++
Âdevice-types/net/driver-conformance.tex |Â 1 +
Â2 files changed, 71 insertions(+)
diff --git a/device-types/net/description.tex b/device-types/net/description.tex
index 76585b0..2deb060 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
Â\item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control
  Âchannel.
+\item[VIRTIO_NET_F_RSS_CONTEXT(50)] Device supports multiple RSS contexts.
+
Â\item[VIRTIO_NET_F_HASH_TUNNEL(51)] Device supports inner header hash for encapsulated packets.
Â\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
Â\item[VIRTIO_NET_F_RSS] Requires VIRTIO_NET_F_CTRL_VQ.
Â\item[VIRTIO_NET_F_VQ_NOTF_COAL] Requires VIRTIO_NET_F_CTRL_VQ.
Â\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.
Â\end{description}
Â\subsubsection{Legacy Interface: Feature bits}\label{sec:Device Types / Network Device / Feature bits / Legacy Interface: Feature bits}
@@ -179,6 +182,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
    Âle16 rss_max_indirection_table_length;
    Âle32 supported_hash_types;
    Âle32 supported_tunnel_types;
+Â Â Â Â le16 max_rss_contexts;
+Â Â Â Â le16 reserved;
Â};
Â\end{lstlisting}
@@ -235,6 +240,12 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
ÂEncapsulation types are defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets /
ÂHash calculation for incoming packets / Encapsulation types supported/enabled for inner header hash}.
+Field \field{max_rss_contexts} only exists if VIRTIO_NET_F_RSS_CONTEXT is set.
+This field specifies the maximum number of RSS contexts \ref{sec:Device Types / Network Device /
+Device Operation / Control Virtqueue / RSS Context} supported by the device.
+
+Field \field{reserved} contains zeroes and is reserved.
+
Â\devicenormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
ÂThe device MUST set \field{max_virtqueue_pairs} to between 1 and 0x8000 inclusive,
@@ -285,6 +296,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Network Device
ÂThe device SHOULD NOT offer VIRTIO_NET_F_CTRL_RX_EXTRA if it
Âdoes not offer VIRTIO_NET_F_CTRL_VQ.
+The device MUST set \field{max_rss_contexts} to at least 1 if it offers VIRTIO_NET_F_RSS_CONTEXT.
+
Â\drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
ÂThe driver MUST NOT write to any of the device configuration fields.
@@ -1606,6 +1619,63 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
Â\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.
Â\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 the VIRTIO_NET_F_RSS feature is implicitly considered the default RSS context.
+
+The device offers the feature VIRTIO_NET_F_RSS_CONTEXT if it supports one or more RSS contexts (excluding the default RSS context
+supported by VIRTIO_NET_F_RSS) and configurable parameters.
+
+\begin{lstlisting}
+struct virtnet_rss_ctx_add_modify {
+Â Â u8 rss_ctx_id;
+Â Â u8 padding[3];
+Â Â struct virtio_net_rss_config rss;
+};
+
+struct virtnet_rss_ctx_del {
+Â Â u8 rss_ctx_id;
+};
+
+#define VIRTNET_RSS_CTX_CTRL 8
+ #define VIRTNET_RSS_CTX_CTRL_ADDÂ 0
+ #define VIRTNET_RSS_CTX_CTRL_MODÂ 1
+ #define VIRTNET_RSS_CTX_CTRL_DELÂ 2
+\end{lstlisting}
+
+RSS context parameters:
+\begin{itemize}
+\item \field{rss_ctx_id}: ID of the specific RSS context.
+\item \field{rss}: Configure 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 to configure a specific RSS context:
+\begin{enumerate}
+\item VIRTNET_RSS_CTX_CTRL_ADD: use the structure virtnet_rss_ctx_add_modify to
+Â Â Â Âadd 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
+Â Â Â Âconfigure 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
+Â Â Â Âthe RSS context whose id is \field{rss_ctx_id} for the device.
+\end{enumerate}
+
+For VIRTNET_RSS_CTX_CTRL_ADD and VIRTNET_RSS_CTX_CTRL_MOD commands, the structure virtnet_rss_ctx_add_modify is read-only for the device.
+For the VIRTNET_RSS_CTX_CTRL_DEL command, the structure virtnet_rss_ctx_del is read-only for the device.
+
+\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 VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command when the device has responded to the VIRTNET_RSS_CTX_CTRL_ADD command with VIRTIO_NET_OK.
+
Â\paragraph{Offloads State Configuration}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue / Offloads State Configuration}
ÂIf the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is negotiated, the driver can
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 @@
Â\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS) }
Â\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Notifications Coalescing}
Â\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}
Â\end{itemize}
--
2.19.1.6.gb485710b
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