Re: [virtio-comment] Re: [PATCH v4 1/1] 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" <ybendito@redhat.com>
> Cc: "Yuri Benditovich" <yuri.benditovich@daynix.com>,
> virtio-comment@lists.oasis-open.org
> Sent: Wednesday, February 19, 2020 4:56:04 PM
> Subject: Re: [virtio-comment] Re: [PATCH v4 1/1] virtio-net: Define
> per-packet hash reporting feature

> On Wed, Feb 19, 2020 at 09:49:37AM -0500, Yuri Benditovich wrote:
> >
> >
> > ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> >
> > From: "Michael S. Tsirkin" <mst@redhat.com>
> > To: "Yuri Benditovich" <ybendito@redhat.com>
> > Cc: "Yuri Benditovich" <yuri.benditovich@daynix.com>,
> > virtio-comment@lists.oasis-open.org
> > Sent: Wednesday, February 19, 2020 4:35:49 PM
> > Subject: Re: [virtio-comment] Re: [PATCH v4 1/1] virtio-net: Define
> > per-packet hash reporting feature
> >
> > On Wed, Feb 19, 2020 at 06:07:13AM -0500, Yuri Benditovich wrote:
> > >
> > >
> > >
> > ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
> > >
> > > From: "Michael S. Tsirkin" <mst@redhat.com>
> > > To: "Yuri Benditovich" <yuri.benditovich@daynix.com>
> > > Cc: virtio-comment@lists.oasis-open.org
> > > Sent: Wednesday, February 19, 2020 11:12:40 AM
> > > Subject: [virtio-comment] Re: [PATCH v4 1/1] virtio-net: Define
> > per-packet
> > > hash reporting feature
> > >
> > > On Wed, Feb 19, 2020 at 09:53:37AM +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>
> > > > ---
> > > > content.tex | 347
> > ++++++++++++++++++++++++++++++++++------------------
> > > > 1 file changed, 229 insertions(+), 118 deletions(-)
> > > >
> > > > diff --git a/content.tex b/content.tex
> > > > index b91a132..d7d4e42 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(57)] 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.
> > > >
> > > > @@ -2995,35 +2998,17 @@ \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 or VIRTIO_NET_F_HASH_REPORT is set.
> > > >
> > > > -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}
> > > >
> > > > @@ -3048,7 +3033,7 @@ \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.
> > > > @@ -3195,6 +3180,8 @@ \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)
> > > > };
> > >
> > > Just noticed this - it's a bit problematic as it might force
> > > compilers to add 2 bytes of padding at the end. Let's add extra 2
> > bytes
> > > of padding explicitly?
> > >
> > > OK, no problem
> > >
> > >
> > >
> > >
> > > > \end{lstlisting}
> > > >
> > > > @@ -3517,6 +3504,12 @@ \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
> > > >
> > > > @@ -3619,6 +3612,181 @@ \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}
> > > > +
> > > > +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 'Enabled hash types' bitmask.
> > > > +\item The device uses a key as defined in \field{hash_key_data}
> > and \
> > > field{hash_key_length} of the virtio_net_rss_config structure (see
> > > > +\ref{sec:Device Types / Network Device / Device Operation /
> > Control
> > > Virtqueue / Receive-side scaling (RSS) / Setting RSS parameters}).
> > > > +\end{itemize}
> > > > +
> > > > +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 'Enabled hash types' bitmask.
> > > > +\item The device uses a key as defined in \field{hash_key_data}
> > and \
> > > field{hash_key_length} of the virtio_net_hash_config structure (see
> > > > +\ref{sec:Device Types / Network Device / Device Operation /
> > Control
> > > Virtqueue / Automatic receive steering in multiqueue mode / Hash
> > > calculation}).
> > > > +\end{itemize}
> > > > +
> > > > +Note that if the device offers VIRTIO_NET_F_HASH_REPORT, even if
> > it
> > > supports only one pair of virtqueues, it MUST 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 MUST 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}
> > > > +
> > > > +If VIRTIO_NET_F_HASH_REPORT 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)
> > >
> > >
> > > So hash_type is the HASH_REPORT value then? That's quite confusing.
> > > Let's rename to hash_report?
> > >
> > > No problem to rename anything, but I'd like to do it one time.
> > > Currently meaningful hash report values are (1..9), 0 for none
> > > They correspond to bitmask of 9 bits for enabled/supported.
> > > It was possible to use the same definitions for enable/support/report
> > > but then reported kind of hash should be 4 bytes.
> > > As you anyway suggests padding at the end of the packet, we can do that,
> > > i.e. add (32 bit hash + 32 bit type)
> >
> > We can but it seems like a waste, does it not? padding can be used for
> > something later ...
> >
> > > Or if we stay with the values as they are now:
> > > values 0..9 - VIRTIO_NET_WHAT?
> >
> > I thought that's VIRTIO_NET_HASH_REPORT_XXX
> >
> > OK, this is exactly what is defined
> >
> >
> > > bits from 0 to 8 - VIRTIO_NET_WHAT?
> >
> >
> > and this one VIRTIO_NET_HASH_TYPE_XXX?
> >
> > OK, this is also exactly what is defined
> >

> Right I'm saying what's defined is fine, just call the fields
> consistently.

> >
> >
> > Generally what you did here is a bit unusual. Mostly we just define
> > bit numbers
> > #define VIRTIO_SCSI_F_INOUT 0
> > #define VIRTIO_SCSI_F_HOTPLUG 1
> > #define VIRTIO_SCSI_F_CHANGE 2
> > #define VIRTIO_SCSI_F_T10_PI 3
> >
> >
> > Value 0 of hash_report is "no hash calculated" and it does not
> > participate in support/enable mask. I did not want to
> > use value other than zero for "no hash".

> Oh right.

> > So you want bit 0 to be reserved (not used) in enable/support mask
> > and then to have all the VIRTIO_NET_HASH_TYPE_XXX to be
> > exactly 1 << VIRTIO_NET_HASH_REPORT_XXX? Just say...
> >

> We can do that too but it's up to you really.

> So fixing the below you would say
> bit 0 curresponding to value 1,
> bit 1 corresponding to value 2 etc.
> No bit corresponds to value 0
> ?

Currently defined: 

Reports: 
VIRTIO_NET_HASH_REPORT_NONE 0 
VIRTIO_NET_HASH_REPORT_IPv4 1 
VIRTIO_NET_HASH_REPORT_UDPv4 3 
VIRTIO_NET_HASH_REPORT_UDPv6_EX 9 

Bitmask (VIRTIO_NET_HASH_TYPE_XXX = 1 << (VIRTIO_NET_HASH_REPORT_XXX - 1)): 
VIRTIO_NET_HASH_TYPE_IPv4 = (1 << 0) 
VIRTIO_NET_HASH_TYPE_UDPv4 = (1 << 2) 
VIRTIO_NET_HASH_TYPE_UDP_EX = (1 << 8) 

How you want it to be changed? 
Can you please write here in the same format? 

> >
> > and just say that bit numbers are from this table, with bit
> > 0 corresponding to the value 0, bit 1 to value 1 etc.
> >
> >
> > maybe that would have been easier on the eyes - I didn't try,
> > I'm not even sure.
> >
> > But what you have is correct enough, we can always try to
> > improve the wording later.
> >
> >
> > >
> > >
> > > > +
> > > > +\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
> > > > @@ -3896,6 +4064,7 @@ \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.
> > > > @@ -3961,10 +4130,37 @@ \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 was negotiated and the device uses
> > automatic
> > > receive steering,
> > > > +the device MUST support a command to configure hash calculation
> > > parameters.
> > > > +
> > > > +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 match the layout of 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}
> > > >
> > > > @@ -3981,7 +4177,8 @@ \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
> > > > @@ -3995,93 +4192,7 @@ \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}
> > > > +Fields \field{hash_key_length} and \field{hash_key_data} define
> > the key
> > > to be used in hash calculation.
> > > >
> > > > \drivernormative{\subparagraph}{Setting RSS parameters}{Device
> > Types /
> > > Network Device / Device Operation / Control Virtqueue / Receive-side
> > > scaling (RSS) }
> > > >
> > > > @@ -4093,12 +4204,12 @@ \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}
> > > > --
> > > > 2.17.1
> > >
> > >
> > > This publicly archived list offers a means to provide input to the
> > > OASIS Virtual I/O Device (VIRTIO) TC.
> > >
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> > >
> > >
> > >
> >
> >
> >

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