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Subject: RE: [EXT] [virtio-dev] Re: [virtio-comment] [PATCH v2] virtio-net: support the RSS context
> -----Original Message-----
> From: virtio-dev@lists.oasis-open.org <virtio-dev@lists.oasis-open.org>
> On Behalf Of Heng Qi
> Sent: Tuesday, September 5, 2023 7:04 PM
> To: virtio-comment@lists.oasis-open.org; virtio-dev@lists.oasis-open.org
> Cc: Michael S . Tsirkin <mst@redhat.com>; Parav Pandit
> <parav@nvidia.com>; Jason Wang <jasowang@redhat.com>; Xuan Zhuo
> <xuanzhuo@linux.alibaba.com>; Yuri Benditovich
> <yuri.benditovich@daynix.com>
> Subject: [EXT] [virtio-dev] Re: [virtio-comment] [PATCH v2] virtio-net:
> support the RSS context
>
> External Email
>
> ----------------------------------------------------------------------
> Hi all!
>
> Do you have any comments on this?
>
> Thanks!
>
> å 2023/9/1 äå5:34, Heng Qi åé:
> > 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://urldefense.proofpoint.com/v2/url?u=https-
> 3A__lists.oasis-2Dopen.org_archives_virtio-
> 2Dcomment_202308_msg00194.html&d=DwIDaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=NHDPs
> fcAYlN2z-
> NXHHG4WB09qqS0voo_nf6_kGS625A&m=4OCN2dGMPgHxDFGtU81zZGzzaFYjTALBtQsWL230
> DoinsHzHA-
> RVOOoF4XqITQuy&s=8MdvZRKdXb3tdMZuldE3Ed6VGmaKPPxc8vGxVyRb_Qc&e= ).
> >
> > An RSS context consists of configurable parameters specified by
> receive-side scaling.
> >
> > Use case:
> > 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 \
> > 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.
> >
> > Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
> > Signed-off-by: Parav Pandit <parav@nvidia.com>
> > ---
> > 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.
> > +
What happens if a rss context with flow classification rules associated
with it is deleted? Are the rules are also then deleted?
Or is such a delete operation not allowed? Can we add a statement describing
the behavior?
Otherwise looks good to me.
Regards
Satananda
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