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Subject: RE: [virtio-dev] RE: [EXT] [virtio-dev] Re: [virtio-comment] [PATCH v2] virtio-net: support the RSS context
> -----Original Message-----
> From: Heng Qi <hengqi@linux.alibaba.com>
> Sent: Monday, October 9, 2023 7:15 PM
> To: Satananda Burla <sburla@marvell.com>; 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: Re: [virtio-dev] RE: [EXT] [virtio-dev] Re: [virtio-comment]
> [PATCH v2] virtio-net: support the RSS context
>
> Hi Satananda!
>
> å 2023/10/10 äå7:46, Satananda Burla åé:
> >
> >> -----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 RSS context cannot be deleted when it is referenced by a rule in
> RFF.
> The RSS context can then be deleted when all rules that referenced it
> have been removed.
>
> Why is this not added to the requirement:
> RSS context is not yet referenced by RFF (i.e. the destination of RFF is
> a single rxq). This is because
> we keep the RSS context and RFF orthogonal for the time being. So that
> the RSS context does
> not block the advancement of RFF.
>
> Also, RFF is not merged into mainline now. When the RSS context is
> complete, we can update
> the statement in the RFF requirements; or when the RFF is complete, we
> can update the statement
> in both the RFF and RSS context.
Ok thanks.
Acked by: Satananda Burla <sburla@marvell.com>
>
> Thanks!
>
> > the behavior?
> > Otherwise looks good to me.
> >
> > Regards
> > Satananda
> >
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