RE: [PATCH v6 1/5] virtio-net: Add theory of operation for flow filter

[Parav Pandit <parav@nvidia.com>]

> From: Cornelia Huck <cohuck@redhat.com>
> Sent: Wednesday, November 22, 2023 6:53 PM


> On Fri, Nov 10 2023, Parav Pandit <parav@nvidia.com> wrote:
> 
> > diff --git a/device-types/net/description.tex
> > b/device-types/net/description.tex
> > index aff5e08..30220b5 100644
> > --- a/device-types/net/description.tex
> > +++ b/device-types/net/description.tex
> > @@ -33,6 +33,9 @@ \subsection{Virtqueues}\label{sec:Device Types /
> > Network Device / Virtqueues}  controlq is optional; it only exists if
> > VIRTIO_NET_F_CTRL_VQ is  negotiated.
> >
> > +The flow filter virtqueues are optional; it may exists only if
> > +VIRTIO_NET_F_FLOW_FILTER is negotiated and if the device reports such
> capability.
> 
> I first thought we should just reword this... but what does "such capability"
> actually mean? If the feature is negotiated, there are M flow filter virtqueues
> at positions 2N+1..2N+M, with the value of M exposed by the device? I think
> we need to list those virtqueues explicitly, otherwise it is confusing.
>
I am going to remove this left over of flow filter virtqueues text.
It was removed.
Good catch.

Ack for rest of the below comments.

> (...)
> 
> > +Each flow filter consists of one or more match key, a flow filter
> > +priority,
> 
> s/key/keys/
> 
> > +a flow filter identifier, an action to forward a packet to the
> > +destination or to drop the packet.
> 
> (...)
> 
> > +The flow filter group can have one or more flow filters. Within a
> > +flow
> 
> s/The/A/
> 
> > +filter group, a packet may find a match to multiple flow filters. In
> > +such
> 
> s/find a match to/match/
> s/such/such a/
> 
> > +scenario, a flow filter with the highest priority is applied first to
> > +the packet, if there is no match, the next higher priority flow filter is
> applied.
> 
> Slightly confusing... maybe
> 
> "In such a scenario, of the matching flow filters the one with the highest
> priority is applied, skipping any matching filters with a lower priority."
> 
> (At least, that's how I interpret this.)
> 
> 
> > +
> > +\paragraph{Packet Processing Order}\label{sec:sec:Device Types /
> > +Network Device / Device Operation / Flow Filter / Packet Processing
> > +Order}
> > +
> > +Whichever filtering and steering functionality is enabled, they are
> > +applied in the following order for the received packet:
> 
> "If enabled, filtering and steering functionalities are applied to the received
> packet in the following order:" ?
> 
> > +
> > +\begin{itemize}
> > +\item apply device configuration done using control virtqueue commands
> > +      VIRTIO_NET_CTRL_RX, VIRTIO_NET_CTRL_MAC and
> VIRTIO_NET_CTRL_VLAN.
> > +\item apply flow filter configuration done using flow filter requests.
> > +\item apply device configuration done using command
> > +      VIRTIO_NET_CTRL_MQ_RSS_CONFIG.
> > +\end{itemize}
> > +
> > +While processing a received packet, at any stage if the packet is
> > +dropped,
> 
> "if the packet is dropped at any stage"
> 
> > +the next level of processing is omitted.
> 
> "the following levels of processing are omitted"
> 
> > +
> > +When a flow filter is matched for the packet, it also stops the
> > +processing of the packet for next stage.
> 
> "If a flow filter is matched for the packet, the following levels of processing
> are omitted as well." ?
> 
> > +
> > +Few examples are:
> 
> s/Few/A few/
> 
> > +\begin{itemize}
> > +\item If the packet is dropped by the flow filter configuration, RSS
> > +      configuration is not applied to such a packet.
> > +\item If the packet is forwarded to a specific receiveq using flow filters,
> > +      RSS configuration is not applied to such a packet due to a match on the
> > +      flow filter request.
> > +\item If the packet is dropped due to VIRTIO_NET_CTRL_MAC
> configuration,
> > +      flow filters or RSS configuration is not applied to such a packet.
> 
> "neither flow filters nor RSS configuration are applied"
> 
> > +\item If the packet does not find any match in any of the flow filter
> groups,
> > +      next level RSS device configuration is applied if its exists.
> > +\item If there are three flow filter groups configured as group_A, group_B
> > +      and group_C with respective priorities as 4, 5, and 6; flow
> > +filters of
> 
> s/flow filters/the flow filters/
> 
> > +      group_C is applied first having highest group priority, if
> > + there is a match,
> 
> s/is applied/are applied/
> 
> > +      flow filters of group_B and group_A are skipped; if there is no match
> for
> > +      the flow filters in group_C, the flow filters of next level group_B are
> applied.
> > +\end{itemize}
> > +
> > +\label{sec:Device Types / Network Device / Device Operation / Control
> > +Virtqueue / Setting Promiscuous Mode}%old label for latexdiff
> >  \subsubsection{Control Virtqueue}\label{sec:Device Types / Network
> > Device / Device Operation / Control Virtqueue}
> >
> >  The driver uses the control virtqueue (if VIRTIO_NET_F_CTRL_VQ is