From: "Michael S. Tsirkin" <mst@redhat.com>
To: Parav Pandit <parav@nvidia.com>
Cc: virtio-dev@lists.oasis-open.org, pasic@linux.ibm.com,
cohuck@redhat.com, virtio-comment@lists.oasis-open.org,
shahafs@nvidia.com
Subject: [virtio-dev] Re: [PATCH v4 8/8] virtio-net: Describe RSS using receive queue handle
Date: Wed, 22 Mar 2023 19:03:42 -0400 [thread overview]
Message-ID: <20230322184932-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20230322215243.249524-9-parav@nvidia.com>
On Wed, Mar 22, 2023 at 11:52:43PM +0200, Parav Pandit wrote:
> The content of indirection table and unclassified_queue which are
> based on math calculation historically. To better describe this, to
> avoid intermixing array index with virtqueue index and to use virtqueue
> number
>
> introduce a field rq_handle (receive queue handle) and refer them
> to describe unclassified_queue and indirection_table fields.
>
> As part of it, have the example that uses non zero virtqueue
> number which helps to have better mapping between receiveX
> object with virtqueue number and the actual value in the
> indirection table.
>
> Fixes: https://github.com/oasis-tcs/virtio-spec/issues/163
> Signed-off-by: Parav Pandit <parav@nvidia.com>
getting there, I feel however there's still too much focus on
rq_id. It's just a struct we use. What matters is the vqn.
More comments below.
> ---
> changelog:
> v3->v4:
> - renamed rq_handle to rss_rq_id
> - moved rss_rq_id definition close to its usage in rss_config struct
> v2->v3:
> - moved rq_handle definition before using it
> - removed duplicate example as rq_handle is now described first
> v0->v1:
> - new patch suggested by Michael Tsirkin
> ---
> device-types/net/description.tex | 27 ++++++++++++++++++++-------
> 1 file changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/device-types/net/description.tex b/device-types/net/description.tex
> index 435c1fc..8b560f3 100644
> --- a/device-types/net/description.tex
> +++ b/device-types/net/description.tex
> @@ -1423,11 +1423,16 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
>
> Driver sends a VIRTIO_NET_CTRL_MQ_RSS_CONFIG command using the following format for \field{command-specific-data}:
> \begin{lstlisting}
> +struct rss_rq_id {
> + le16 vqn_1_16: 15; /* Bits 1 to 16 of the virtqueue number */
> + le16 reserved: 1; /* Set to zero */
> +};
> +
> struct virtio_net_rss_config {
> le32 hash_types;
> le16 indirection_table_mask;
> - le16 unclassified_queue;
> - le16 indirection_table[indirection_table_length];
> + struct rss_rq_id unclassified_queue;
> + struct rss_rq_id indirection_table[indirection_table_length];
> le16 max_tx_vq;
> u8 hash_key_length;
> u8 hash_key_data[hash_key_length];
> @@ -1442,10 +1447,15 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> \field{indirection_table} array.
> Number of entries in \field{indirection_table} is (\field{indirection_table_mask} + 1).
>
> -Field \field{unclassified_queue} contains the 0-based index of
> -the receive virtqueue to place unclassified packets in. Index 0 corresponds to receiveq1.
> +\field{rss_rq_id} is a receive virtqueue id. \field{vqn_1_16}
Looks like you keep removing the main thing which is *what is this field
actually for*.
More comments:
id is actually abbreviation. Field is actually \field{unclassified_queue} -
rss_rq_id is just a name of struct has no meaning by itself.
so either \field{struct rss_rq_id} or just don't mention this at all.
Below example on how not to mention at all.
Here's one way to put it:
\field{unclassified_queue} identifies a receive virtqueue
to place unclassified packets in. Within \field{unclassified_queue}, \field{vqn_1_16},
consists of bits 1 to 16 of the receive virtqueue number
For example,
\field{vqn_1_16} value of 3 corresponds to virtqueue number 6 maps to receiveq4.
> +consists of bits 1 to 16 of virtqueue number. For example,
> +\field{vqn_1_16} value of 3 corresponds to virtqueue number 6 maps to receiveq4.
> +
> +Field \field{unclassified_queue} contains the receive virtqueue
> +id \field{rss_rq_id} described above.
>
> -Field \field{indirection_table} contains an array of 0-based indices of receive virtqueues. Index 0 corresponds to receiveq1.
> +Field \field{indirection_table} is an array of receive
> +queue ids described above in \field{rss_rq_id}.
Field \field{indirection_table} is an array of receive queue
identifiers, using the same format as \field{unclassified_queue}.
>
> A driver sets \field{max_tx_vq} to inform a device how many transmit virtqueues it may use (transmitq1\ldots transmitq \field{max_tx_vq}).
>
> @@ -1455,7 +1465,8 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
>
> A driver MUST NOT send the VIRTIO_NET_CTRL_MQ_RSS_CONFIG command if the feature VIRTIO_NET_F_RSS has not been negotiated.
>
> -A driver MUST fill the \field{indirection_table} array only with indices of enabled queues. Index 0 corresponds to receiveq1.
> +A driver MUST fill the \field{indirection_table} array only with
> +the \field{rss_rq_id} corresponding to the enabled receive virtqueues.
There's no field like this. Also not "the" virtqueues - we didn't
discuss them previously. Generally if you want to tweak grammar it's
best to do it separately...
example way to put it better:
\field{vqn_1_16} in each entry corresponding to enabled receive virtqueues.
>
> The number of entries in \field{indirection_table} (\field{indirection_table_mask} + 1) MUST be a power of two.
>
> @@ -1468,7 +1479,9 @@ \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Devi
> \begin{itemize}
> \item Calculate the hash of the packet as defined in \ref{sec:Device Types / Network Device / Device Operation / Processing of Incoming Packets / Hash calculation for incoming packets}.
> \item If the device did not calculate the hash for the specific packet, the device directs the packet to the receiveq specified by \field{unclassified_queue} of virtio_net_rss_config structure.
> -\item Apply \field{indirection_table_mask} to the calculated hash and use the result as the index in the indirection table to get 0-based number of destination receiveq.
> +\item Apply \field{indirection_table_mask} to the calculated hash
> +and use the result as the index in the indirection table to get
> +\field{rss_rq_id}.
to get \field{vqn_1_16}
> \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}
>
> --
> 2.26.2
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next prev parent reply other threads:[~2023-03-22 23:03 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-22 21:52 [virtio-dev] [PATCH v4 0/8] Rename queue index to queue number Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 1/8] content: Add vq number text Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 2/8] transport-pci: Refer to the vq by its number Parav Pandit
[not found] ` <68fc71b0-2026-fd99-22f3-d0313e597373@nvidia.com>
2023-03-27 23:19 ` [virtio-dev] RE: [virtio-comment] " Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 3/8] transport-mmio: Rename QueueNum register Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 4/8] transport-mmio: Refer to the vq by its number Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 5/8] transport-ccw: Rename queue depth/size to other transports Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 6/8] transport-ccw: Refer to the vq by its number Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 7/8] virtio-net: Avoid duplicate receive queue example Parav Pandit
2023-03-22 21:52 ` [virtio-dev] [PATCH v4 8/8] virtio-net: Describe RSS using receive queue handle Parav Pandit
2023-03-22 23:03 ` Michael S. Tsirkin [this message]
2023-03-22 23:47 ` [virtio-dev] " Parav Pandit
2023-03-22 23:04 ` [virtio-dev] Re: [PATCH v4 0/8] Rename queue index to queue number Michael S. Tsirkin
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