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Subject: Re: [PATCH v5] virtio-net: support the RSS context
On Fri, 3 Nov 2023 14:36:23 +0800, Heng Qi <hengqi@linux.alibaba.com> wrote:
> 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>
Acked-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> ---
> v4->v5:
> 1. Use 'u8 reserved[6]' instead of u16 padding to align the structure.
>
> v3->v4:
> 1. Rebase to Xuan's device stats patch.
>
> v2->v3:
> 1. Process Satananda's comments and add his 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 aff5e08..61cce1f 100644
> --- a/device-types/net/description.tex
> +++ b/device-types/net/description.tex
> @@ -122,6 +122,8 @@ \subsection{Feature bits}\label{sec:Device Types / Network Device / Feature bits
> device with the same MAC address.
>
> \item[VIRTIO_NET_F_SPEED_DUPLEX(63)] Device reports speed and duplex.
> +
> +\item[VIRTIO_NET_F_RSS_CONTEXT(64)] Device supports multiple RSS contexts.
> \end{description}
>
> \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device / Feature bits / Feature bit requirements}
> @@ -153,6 +155,7 @@ \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}
> @@ -1613,6 +1616,88 @@ \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 9
> + #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;
> + u8 reserved[6];
> + 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{reserved} 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 52526e4..c71341e 100644
> --- a/device-types/net/device-conformance.tex
> +++ b/device-types/net/device-conformance.tex
> @@ -16,4 +16,5 @@
> \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 / Device Statistics}
> +\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 c693c4f..7081ec3 100644
> --- a/device-types/net/driver-conformance.tex
> +++ b/device-types/net/driver-conformance.tex
> @@ -16,4 +16,5 @@
> \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 / Device Statistics}
> +\item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / RSS Context}
> \end{itemize}
> --
> 2.19.1.6.gb485710b
>
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