[virtio-comment] Re: [PATCH v3] virtio-net: Define per-packet hash reporting feature

[Yuri Benditovich <ybendito@redhat.com>]

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----- Original Message -----

> From: "Michael S. Tsirkin" <mst@redhat.com>
> To: "Yuri Benditovich" <yuri.benditovich@daynix.com>
> Cc: virtio-comment@lists.oasis-open.org, ybendito@redhat.com
> Sent: Tuesday, February 18, 2020 7:59:13 AM
> Subject: Re: [PATCH v3] virtio-net: Define per-packet hash reporting feature

> On Wed, Feb 05, 2020 at 08:59:05PM +0200, Yuri Benditovich wrote:
> > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/66
> > Define respective feature bit for virtio-net.
> > Extend packet layout to populate hash value and type.
> > Move the definition of IP/TCP/UDP header fields to
> > calculate the hash out of RSS section to common network
> > device section.
> >
> > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com>

> Looks good to me.
> Minor typos/tweaks.
> Otherwise

> Acked-by: Michael S. Tsirkin <mst@redhat.com>

> > ---
> > content.tex | 347 ++++++++++++++++++++++++++++++++++------------------
> > 1 file changed, 228 insertions(+), 119 deletions(-)
> >
> > diff --git a/content.tex b/content.tex
> > index fb10061..20d598d 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -2895,6 +2895,9 @@ \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_HASH_REPORT(58)] Device can report per-packet hash
> > + value and a type of calculated hash.
> > +
> > \item[VIRTIO_NET_F_GUEST_HDRLEN(59)] Driver can provide the exact
> > \field{hdr_len}
> > value. Device benefits from knowing the exact header length.
> >
> > @@ -2981,35 +2984,17 @@ \subsection{Device configuration
> > layout}\label{sec:Device Types / Network Device
> > le32 supported_hash_types;
> > };
> > \end{lstlisting}
> > -\label{sec:Device Types / Network Device / Device configuration layout /
> > RSS}
> > -Three following fields, \field{rss_max_key_size},
> > \field{rss_max_indirection_table_length}
> > -and \field{supported_hash_types} only exist if VIRTIO_NET_F_RSS is set.
> > +The following field, \field{rss_max_key_size} only exist if
> > VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT is set.
> > +It specifies the maximal supported length of RSS key in bytes.
> >
> > -Field \field{rss_max_key_size} specifies the maximal supported length of
> > RSS key in bytes.
> > +The following field, \field{rss_max_indirection_table_length} only exist
> > if VIRTIO_NET_F_RSS is set.
> > +It specifies the maximal number of 16-bit entries in RSS indirection
> > table.
> >
> > -Field \field{rss_max_indirection_table_length} specifies the maximal
> > number of 16-bit entries in RSS indirection table.
> > +The next field, \field{supported_hash_types} exists only if the device
> > supports hash calculation,
> > +i.e. if VIRTIO_NET_F_RSS of VIRTIO_NET_F_HASH_REPORT is set.

> of -> or?
Yes, will fix the typo 

> >
> > -Field \field{supported_hash_types} contains the bitmask of supported RSS
> > hash types.
> > -
> > -Hash types applicable for IPv4 packets:
> > -\begin{lstlisting}
> > -#define VIRTIO_NET_RSS_HASH_TYPE_IPv4 (1 << 0)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_TCPv4 (1 << 1)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_UDPv4 (1 << 2)
> > -\end{lstlisting}
> > -Hash types applicable for IPv6 packets without extension headers
> > -\begin{lstlisting}
> > -#define VIRTIO_NET_RSS_HASH_TYPE_IPv6 (1 << 3)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_TCPv6 (1 << 4)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_UDPv6 (1 << 5)
> > -\end{lstlisting}
> > -Hash types applicable for IPv6 packets with extension headers
> > -\begin{lstlisting}
> > -#define VIRTIO_NET_RSS_HASH_TYPE_IP_EX (1 << 6)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_TCP_EX (1 << 7)
> > -#define VIRTIO_NET_RSS_HASH_TYPE_UDP_EX (1 << 8)
> > -\end{lstlisting}
> > -For the exact meaning of VIRTIO_NET_RSS_HASH_TYPE_ flags see
> > \ref{sec:Device Types / Network Device / Device Operation / Control
> > Virtqueue / Receive-side scaling (RSS) / RSS hash types}.
> > +Field \field{supported_hash_types} contains the bitmask of supported hash
> > types.
> > +See \ref{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets /
> > Supported/enabled hash types} for details of supported hash types.
> >
> > \devicenormative{\subsubsection}{Device configuration layout}{Device Types
> > / Network Device / Device configuration layout}
> >
> > @@ -3034,7 +3019,7 @@ \subsection{Device configuration
> > layout}\label{sec:Device Types / Network Device
> > negotiated.
> >
> > The device MUST set \field{rss_max_key_size} to at least 40, if it offers
> > -VIRTIO_NET_F_RSS.
> > +VIRTIO_NET_F_RSS or VIRTIO_NET_F_HASH_REPORT.
> >
> > The device MUST set \field{rss_max_indirection_table_length} to at least
> > 128, if it offers
> > VIRTIO_NET_F_RSS.
> > @@ -3159,6 +3144,8 @@ \subsection{Device Operation}\label{sec:Device Types
> > / Network Device / Device O
> > le16 csum_start;
> > le16 csum_offset;
> > le16 num_buffers;
> > + le32 hash_value; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > + le16 hash_type; (Only if VIRTIO_NET_F_HASH_REPORT negotiated)
> > };
> > \end{lstlisting}
> >
> > @@ -3481,6 +3468,12 @@ \subsubsection{Processing of Incoming
> > Packets}\label{sec:Device Types / Network
> >
> > \end{enumerate}
> >
> > +If applicable, the device calculates per-packet hash for incoming packets
> > as
> > +defined in \ref{sec:Device Types / Network Device / Device Operation /
> > Processing of Incoming Packets / Hash calculation for incoming packets}.
> > +
> > +If applicable, the device reports hash information for incoming packets as
> > +defined in \ref{sec:Device Types / Network Device / Device Operation /
> > Processing of Incoming Packets / Hash reporting for incoming packets}.
> > +
> > \devicenormative{\paragraph}{Processing of Incoming Packets}{Device Types /
> > Network Device / Device Operation / Processing of Incoming Packets}
> > \label{devicenormative:Device Types / Network Device / Device Operation /
> > Processing of Packets}%old label for latexdiff
> >
> > @@ -3583,6 +3576,181 @@ \subsubsection{Processing of Incoming
> > Packets}\label{sec:Device Types / Network
> > If neither VIRTIO_NET_HDR_F_NEEDS_CSUM nor
> > VIRTIO_NET_HDR_F_DATA_VALID is set, the driver MUST NOT
> > rely on the packet checksum being correct.
> > +
> > +\paragraph{Hash calculation for incoming packets}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets}
> > +
> > +A device attempts to calculate a per-packet hash in the following cases:
> > +\begin{itemize}
> > +\item The feature VIRTIO_NET_F_RSS was negotiated. The device uses the
> > hash to determine the receive virtqueue to place incoming packets.
> > +\item The feature VIRTIO_NET_F_HASH_REPORT was negotiated. The device
> > reports the hash value and the hash type with the packet.
> > +\end{itemize}

> below mentions structures that were never mentioned earlier.
> We should say a couple of words here.
> E.g.
> the driver configures the hash calculation by sending
> either the virtio_net_rss_config structure as described in
> ... or the
> virtio_net_hash_config structure as described in ... to the device.

OK, will add that 

> > +If the feature VIRTIO_NET_F_RSS was negotiated:
> > +\begin{itemize}
> > +\item The device uses \field{hash_types} of the virtio_net_rss_config
> > structure as the 'Enabled hash types' bitmask.
> > +\item The device uses \field{hash_key_data} of the virtio_net_rss_config
> > structure.

> .. as ... ?

OK 

> Also what about key length field?
> We should document all fields.

> Also I would maybe repeat this near where the structure itself is defined.
OK 

> > +\end{itemize}
> > +See the definition of virtio_net_rss_config structure in \ref{sec:Device
> > Types / Network Device / Device Operation / Control Virtqueue /
> > Receive-side scaling (RSS) / Setting RSS parameters}

> I would just add a link where virtio_net_rss_config is mentioned.
> E.g.
> The device uses \field{hash_key_data} of the virtio_net_rss_config
> structure (See \ref{...}).

OK 

> > +
> > +If the feature VIRTIO_NET_F_RSS was not negotiated:
> > +\begin{itemize}
> > +\item The device uses \field{hash_types} of the virtio_net_hash_config
> > structure as the 'Enabled hash types' bitmask.
> > +\item The device uses \field{hash_key_data} of the virtio_net_hash_config
> > structure.
> > +\end{itemize}
> > +See the definition of virtio_net_hash_config structure in \ref{sec:Device
> > Types / Network Device / Device Operation / Control Virtqueue / Automatic
> > receive steering in multiqueue mode / Hash calculation}.
> > +
> > +Note that if the device offers VIRTIO_NET_F_HASH_REPORT, even if it
> > supports only one pair of virtqueues, it SHOULD support
> > +at least one of commands of VIRTIO_NET_CTRL_MQ class to configure reported
> > hash parameters:
> > +\begin{itemize}
> > +\item If the device offers VIRTIO_NET_F_RSS, it MUST support
> > VIRTIO_NET_CTRL_MQ_RSS_CONFIG command per
> > + \ref{sec:Device Types / Network Device / Device Operation / Control
> > Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}.
> > +\item Otherwise the device SHOULD support VIRTIO_NET_CTRL_MQ_HASH_CONFIG
> > command per
> > + \ref{sec:Device Types / Network Device / Device Operation / Control
> > Virtqueue / Automatic receive steering in multiqueue mode / Hash
> > calculation}.
> > +\end{itemize}
> > +
> > +\subparagraph{Supported/enabled hash types}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets /
> > Supported/enabled hash types}
> > +Hash types applicable for IPv4 packets:
> > +\begin{lstlisting}
> > +#define VIRTIO_NET_HASH_TYPE_IPv4 (1 << 0)
> > +#define VIRTIO_NET_HASH_TYPE_TCPv4 (1 << 1)
> > +#define VIRTIO_NET_HASH_TYPE_UDPv4 (1 << 2)
> > +\end{lstlisting}
> > +Hash types applicable for IPv6 packets without extension headers
> > +\begin{lstlisting}
> > +#define VIRTIO_NET_HASH_TYPE_IPv6 (1 << 3)
> > +#define VIRTIO_NET_HASH_TYPE_TCPv6 (1 << 4)
> > +#define VIRTIO_NET_HASH_TYPE_UDPv6 (1 << 5)
> > +\end{lstlisting}
> > +Hash types applicable for IPv6 packets with extension headers
> > +\begin{lstlisting}
> > +#define VIRTIO_NET_HASH_TYPE_IP_EX (1 << 6)
> > +#define VIRTIO_NET_HASH_TYPE_TCP_EX (1 << 7)
> > +#define VIRTIO_NET_HASH_TYPE_UDP_EX (1 << 8)
> > +\end{lstlisting}
> > +
> > +\subparagraph{IPv4 packets}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets / IPv4
> > packets}
> > +The device calculates the hash on IPv4 packets according to 'Enabled hash
> > types' bitmask as follows:
> > +\begin{itemize}
> > +\item If VIRTIO_NET_HASH_TYPE_TCPv4 is set and the packet has
> > +a TCP header, the hash is calculated over the following fields:
> > +\begin{itemize}
> > +\item Source IP address
> > +\item Destination IP address
> > +\item Source TCP port
> > +\item Destination TCP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_UDPv4 is set and the
> > +packet has a UDP header, the hash is calculated over the following fields:
> > +\begin{itemize}
> > +\item Source IP address
> > +\item Destination IP address
> > +\item Source UDP port
> > +\item Destination UDP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_IPv4 is set, the hash is
> > +calculated over the following fields:
> > +\begin{itemize}
> > +\item Source IP address
> > +\item Destination IP address
> > +\end{itemize}
> > +\item Else the device does not calculate the hash
> > +\end{itemize}
> > +
> > +\subparagraph{IPv6 packets without extension header}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets / IPv6 packets
> > without extension header}
> > +The device calculates the hash on IPv6 packets without extension
> > +headers according to 'Enabled hash types' bitmask as follows:
> > +\begin{itemize}
> > +\item If VIRTIO_NET_HASH_TYPE_TCPv6 is set and the packet has
> > +a TCPv6 header, the hash is calculated over the following fields:
> > +\begin{itemize}
> > +\item Source IPv6 address
> > +\item Destination IPv6 address
> > +\item Source TCP port
> > +\item Destination TCP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_UDPv6 is set and the
> > +packet has a UDPv6 header, the hash is calculated over the following
> > fields:
> > +\begin{itemize}
> > +\item Source IPv6 address
> > +\item Destination IPv6 address
> > +\item Source UDP port
> > +\item Destination UDP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_IPv6 is set, the hash is
> > +calculated over the following fields:
> > +\begin{itemize}
> > +\item Source IPv6 address
> > +\item Destination IPv6 address
> > +\end{itemize}
> > +\item Else the device does not calculate the hash
> > +\end{itemize}
> > +
> > +\subparagraph{IPv6 packets with extension header}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash calculation for incoming packets / IPv6 packets
> > with extension header}
> > +The device calculates the hash on IPv6 packets with extension
> > +headers according to 'Enabled hash types' bitmask as follows:
> > +\begin{itemize}
> > +\item If VIRTIO_NET_HASH_TYPE_TCP_EX is set and the packet
> > +has a TCPv6 header, the hash is calculated over the following fields:
> > +\begin{itemize}
> > +\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > +\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > +\item Source TCP port
> > +\item Destination TCP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_UDP_EX is set and the
> > +packet has a UDPv6 header, the hash is calculated over the following
> > fields:
> > +\begin{itemize}
> > +\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > +\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > +\item Source UDP port
> > +\item Destination UDP port
> > +\end{itemize}
> > +\item Else if VIRTIO_NET_HASH_TYPE_IP_EX is set, the hash is
> > +calculated over the following fields:
> > +\begin{itemize}
> > +\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > +\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > +\end{itemize}
> > +\item Else skip IPv6 extension headers and calculate the hash as
> > +defined for an IPv6 packet without extension headers
> > +(see \ref{sec:Device Types / Network Device / Device Operation /
> > Processing of Incoming Packets / Hash calculation for incoming packets /
> > IPv6 packets without extension header}).
> > +\end{itemize}
> > +
> > +\paragraph{Hash reporting for incoming packets}
> > +\label{sec:Device Types / Network Device / Device Operation / Processing
> > of Incoming Packets / Hash reporting for incoming packets}%old label for
> > latexdiff

> I doubt it's an old label

OK, I'll remove that 

> > +
> > +If feature VIRTIO_NET_F_HASH_REPORT

> If feature VIRTIO_NET_F_HASH_REPORT -> If VIRTIO_NET_F_HASH_REPORT
OK 

> > was negotiated and
> > + the device has calculated the hash for the packet, the device fills
> > \field{hash_type} with the type of calculated hash
> > +and \field{hash_value} with the value of calculated hash.
> > +
> > +If VIRTIO_NET_F_HASH_REPORT was negotiated but due to any reason the
> > +hash was not calculated, the device sets \field{hash_type} to
> > VIRTIO_NET_HASH_REPORT_NONE.
> > +
> > +Possible values that the device can report in \field{hash_type} are
> > defined below.
> > +They correspond to supported hash types defined in
> > +\ref{sec:Device Types / Network Device / Device Operation / Processing of
> > Incoming Packets / Hash calculation for incoming packets /
> > Supported/enabled hash types}
> > +as follows:
> > +
> > +VIRTIO_NET_HASH_TYPE_XXX = 1 << (VIRTIO_NET_HASH_REPORT_XXX - 1)
> > +
> > +\begin{lstlisting}
> > +#define VIRTIO_NET_HASH_REPORT_NONE 0
> > +#define VIRTIO_NET_HASH_REPORT_IPv4 1
> > +#define VIRTIO_NET_HASH_REPORT_TCPv4 2
> > +#define VIRTIO_NET_HASH_REPORT_UDPv4 3
> > +#define VIRTIO_NET_HASH_REPORT_IPv6 4
> > +#define VIRTIO_NET_HASH_REPORT_TCPv6 5
> > +#define VIRTIO_NET_HASH_REPORT_UDPv6 6
> > +#define VIRTIO_NET_HASH_REPORT_IPv6_EX 7
> > +#define VIRTIO_NET_HASH_REPORT_TCPv6_EX 8
> > +#define VIRTIO_NET_HASH_REPORT_UDPv6_EX 9
> > +\end{lstlisting}
> > +
> > \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
> > @@ -3860,6 +4028,7 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> > #define VIRTIO_NET_CTRL_MQ 4
> > #define VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET 0 (for automatic receive steering)
> > #define VIRTIO_NET_CTRL_MQ_RSS_CONFIG 1 (for configurable receive steering)
> > + #define VIRTIO_NET_CTRL_MQ_HASH_CONFIG 2 (for configurable hash
> > calculation)
> > \end{lstlisting}
> >
> > If more than one multiqueue mode is negotiated, the resulting device
> > configuration is defined by the last command sent by the driver.
> > @@ -3925,10 +4094,37 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> > according to the native endian of the guest rather than
> > (necessarily when not using the legacy interface) little-endian.
> >
> > +\subparagraph{Hash calculation}\label{sec:Device Types / Network Device /
> > Device Operation / Control Virtqueue / Automatic receive steering in
> > multiqueue mode / Hash calculation}
> > +If VIRTIO_NET_F_HASH_REPORT negotiated

> negotiated -> was negotiated

OK 

> > and the device uses automatic receive steering,
> > +the device SHOULD support a command to configure hash calculation
> > parameters.

> SHOULD and not MUST do drivers must expect failure and handle
> gracefully?

This corner non-functional case IMO does not present any critical problem to the driver. 
It already has negotiated the feature, so the packet is extended but does not contain a calculated hash. 
OK, I'll change it to MUST. Please respond if you disagree. 

> > +
> > +The driver provides parameters for hash calculation as follows:
> > +
> > +\field{class} VIRTIO_NET_CTRL_MQ, \field{command}
> > VIRTIO_NET_CTRL_MQ_HASH_CONFIG.
> > +
> > +The \field{command-specific-data} has following format:
> > +\begin{lstlisting}
> > +struct virtio_net_hash_config {
> > + le32 hash_types;
> > + le16 reserved[4];
> > + u8 hash_key_length;
> > + u8 hash_key_data[hash_key_length];
> > +};
> > +\end{lstlisting}
> > +Field \field{hash_types} contains a bitmask of allowed hash types as
> > +defined in
> > +\ref{sec:Device Types / Network Device / Device Operation / Processing of
> > Incoming Packets / Hash calculation for incoming packets /
> > Supported/enabled hash types}.
> > +Initially the device has all hash types disabled and reports only
> > VIRTIO_NET_HASH_REPORT_NONE.
> > +
> > +Field \field{reserved} MUST contain zeroes. It is defined to make the
> > structure to look similar

> look similar -> match the layout of
OK 

> > to virtio_net_rss_config structure,
> > +defined in \ref{sec:Device Types / Network Device / Device Operation /
> > Control Virtqueue / Receive-side scaling (RSS)}.
> > +
> > +Fields \field{hash_key_length} and \field{hash_key_data} define the key to
> > be used in hash calculation.
> > +
> > \paragraph{Receive-side scaling (RSS)}\label{sec:Device Types / Network
> > Device / Device Operation / Control Virtqueue / Receive-side scaling
> > (RSS)}
> > A device offers the feature VIRTIO_NET_F_RSS if it supports RSS receive
> > steering with Toeplitz hash calculation and configurable parameters.
> >
> > -A driver queries RSS capabilities of the device by reading device
> > configuration as defined in \ref{sec:Device Types / Network Device /
> > Device configuration layout / RSS}
> > +A driver queries RSS capabilities of the device by reading device
> > configuration as defined in \ref{sec:Device Types / Network Device /
> > Device configuration layout}
> >
> > \subparagraph{Setting RSS parameters}\label{sec:Device Types / Network
> > Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS)
> > / Setting RSS parameters}
> >
> > @@ -3945,7 +4141,8 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> > };
> > \end{lstlisting}
> > Field \field{hash_types} contains a bitmask of allowed hash types as
> > -defined in \ref{sec:Device Types / Network Device / Device Operation /
> > Control Virtqueue / Receive-side scaling (RSS) / RSS hash types}.
> > +defined in
> > +\ref{sec:Device Types / Network Device / Device Operation / Processing of
> > Incoming Packets / Hash calculation for incoming packets /
> > Supported/enabled hash types}.
> >
> > Field \field{indirection_table_mask} is a mask to be applied to
> > the calculated hash to produce an index in the
> > @@ -3959,94 +4156,6 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> >
> > 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}).
> >
> > -\subparagraph{RSS hash types}\label{sec:Device Types / Network Device /
> > Device Operation / Control Virtqueue / Receive-side scaling (RSS) / RSS
> > hash types}
> > -
> > -The device calculates the hash on IPv4 packets according to the
> > -field \field{hash_types} of the virtio_net_rss_config structure as
> > follows:
> > -\begin{itemize}
> > -\item If VIRTIO_NET_RSS_HASH_TYPE_TCPv4 is set and the packet has
> > -a TCP header, the hash is calculated over the following fields:
> > -\begin{itemize}
> > -\item Source IP address
> > -\item Destination IP address
> > -\item Source TCP port
> > -\item Destination TCP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDPv4 is set and the
> > -packet has a UDP header, the hash is calculated over the following fields:
> > -\begin{itemize}
> > -\item Source IP address
> > -\item Destination IP address
> > -\item Source UDP port
> > -\item Destination UDP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_IPv4 is set, the hash is
> > -calculated over the following fields:
> > -\begin{itemize}
> > -\item Source IP address
> > -\item Destination IP address
> > -\end{itemize}
> > -\item Else the device does not calculate the hash
> > -\end{itemize}
> > -
> > -\label{itm:Device Types / Network Device / Device Operation / Control
> > Virtqueue / Receive-side scaling (RSS) / RSS hash types/hash on IPv6
> > packets without extension headers}
> > -The device calculates the hash on IPv6 packets without extension
> > -headers according to the field \field{hash_types} of the
> > virtio_net_rss_config structure as follows:
> > -\begin{itemize}
> > -\item If VIRTIO_NET_RSS_HASH_TYPE_TCPv6 is set and the packet has
> > -a TCPv6 header, the hash is calculated over the following fields:
> > -\begin{itemize}
> > -\item Source IPv6 address
> > -\item Destination IPv6 address
> > -\item Source TCP port
> > -\item Destination TCP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDPv6 is set and the
> > -packet has a UDPv6 header, the hash is calculated over the following
> > fields:
> > -\begin{itemize}
> > -\item Source IPv6 address
> > -\item Destination IPv6 address
> > -\item Source UDP port
> > -\item Destination UDP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_IPv6 is set, the hash is
> > -calculated over the following fields:
> > -\begin{itemize}
> > -\item Source IPv6 address
> > -\item Destination IPv6 address
> > -\end{itemize}
> > -\item Else the device does not calculate the hash
> > -\end{itemize}
> > -
> > -The device calculates the hash on IPv6 packets with extension
> > -headers according to the field \field{hash_types} of the
> > virtio_net_rss_config structure as follows:
> > -\begin{itemize}
> > -\item If VIRTIO_NET_RSS_HASH_TYPE_TCP_EX is set and the packet
> > -has a TCPv6 header, the hash is calculated over the following fields:
> > -\begin{itemize}
> > -\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > -\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > -\item Source TCP port
> > -\item Destination TCP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_UDP_EX is set and the
> > -packet has a UDPv6 header, the hash is calculated over the following
> > fields:
> > -\begin{itemize}
> > -\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > -\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > -\item Source UDP port
> > -\item Destination UDP port
> > -\end{itemize}
> > -\item Else if VIRTIO_NET_RSS_HASH_TYPE_IP_EX is set, the hash is
> > -calculated over the following fields:
> > -\begin{itemize}
> > -\item Home address from the home address option in the IPv6 destination
> > options header. If the extension header is not present, use the Source
> > IPv6 address.
> > -\item IPv6 address that is contained in the Routing-Header-Type-2 from the
> > associated extension header. If the extension header is not present, use
> > the Destination IPv6 address.
> > -\end{itemize}
> > -\item Else skip IPv6 extension headers and calculate the hash as
> > -defined for an IPv6 packet without extension headers (see \ref{itm:Device
> > Types / Network Device / Device Operation / Control Virtqueue /
> > Receive-side scaling (RSS) / RSS hash types/hash on IPv6 packets without
> > extension headers}).
> > -\end{itemize}
> > -
> > \drivernormative{\subparagraph}{Setting RSS parameters}{Device Types /
> > Network Device / Device Operation / Control Virtqueue / Receive-side
> > scaling (RSS) }
> >
> > A driver MUST NOT send the VIRTIO_NET_CTRL_MQ_RSS_CONFIG command if the
> > feature VIRTIO_NET_F_RSS has not been negotiated.
> > @@ -4057,12 +4166,12 @@ \subsubsection{Control Virtqueue}\label{sec:Device
> > Types / Network Device / Devi
> >
> > A driver MUST use \field{indirection_table_mask} values that are less than
> > \field{rss_max_indirection_table_length} reported by a device.
> >
> > -A driver MUST NOT set any VIRTIO_NET_RSS_HASH_TYPE_ flags that are not
> > supported by a device.
> > +A driver MUST NOT set any VIRTIO_NET_HASH_TYPE_ flags that are not
> > supported by a device.
> >
> > \devicenormative{\subparagraph}{RSS processing}{Device Types / Network
> > Device / Device Operation / Control Virtqueue / Receive-side scaling (RSS)
> > / RSS processing}
> > The device MUST determine the destination queue for a network packet as
> > follows:
> > \begin{itemize}
> > -\item Calculate the hash of the packet as defined in \ref{sec:Device Types
> > / Network Device / Device Operation / Control Virtqueue / Receive-side
> > scaling (RSS) / RSS hash types}
> > +\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 (value of 0
> > corresponds to receiveq1).
> > \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 (value of 0 corresponds to receiveq1).
> > \end{itemize}
> > --

I'll prepare the next drop with these minimal changes. 

> > 2.17.1

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