On Sat, Apr 28, 2018 at 1:09 AM, Vijayabhaskar Balakrishna < [email protected]> wrote:
> Hi Sameeh, > > See inline.. > > Thanks, > Vijay > > On 4/18/2018 3:46 AM, Sameeh Jubran wrote: > >> From: Sameeh Jubran <[email protected]> >> >> This commit introduces the RSS feature into virtio-net. It is introduced >> as a sub mode for a general command which configures the steering mode. >> >> Most modern high end network devices today support configurable hash >> functions, >> this commit introduces RSS - Receive Side Scaling - [1] to virtio net >> device. >> >> The RSS is a technology from Microsoft that boosts network device >> performance >> by efficiently distributing the traffic among the CPUs in a multiprocessor >> system. >> >> This feature is supported in most of the modern network cards as well as >> most >> modern OSes including Linux and Windows. It is worth mentioning that both >> DPDK >> and Hyper-v support RSS too. >> >> [1] https://docs.microsoft.com/en-us/windows-hardware/drivers/ne >> twork/ndis-receive-side-scaling2 >> >> Signed-off-by: Sameeh Jubran <[email protected]> >> --- >> content.tex | 109 ++++++++++++++++++++++++++++++ >> ++++++++++++++++++++++++++++++ >> 1 file changed, 109 insertions(+) >> >> diff --git a/content.tex b/content.tex >> index 6b1f7ca..3ea2b6a 100644 >> --- a/content.tex >> +++ b/content.tex >> @@ -4023,6 +4023,7 @@ according to the native endian of the guest rather >> than >> \begin{lstlisting} >> // steering mode flags >> #define STEERING_MODE_AUTO 0x1 >> +#define STEERING_MODE_RSS 0x2 >> // Used by the devide for returning to the driver the supported >> steering modes >> struct virtio_net_steering_modes { >> @@ -4035,6 +4036,7 @@ le32 command; >> // A union which can be used for passing structures to one of the sub >> modes >> union { >> + struct virtio_net_rss rss_conf; >> } >> }; >> @@ -4074,6 +4076,113 @@ If this feature has been negotiated, the virtio >> header has an additional >> This is the default steering mode, please refer to the "Automatic >> receive steering in multiqueue" section. >> +\subparagraph{Receive Side Scaling}{Device Types / Network Device / >> Device Operation / Control Virtqueue / Steering mode / Receive Side Scaling} >> + >> +\begin{lstlisting} >> +#define RSS_HASH_FUNCTION_TOEPLITZ 0x1 >> +#define RSS_HASH_FUNCTION_SYMMETRIC 0x2 >> + >> +// Hash function fields >> +#define RSS_HASH_FIELDS_IPV4 0x00000100 >> +#define RSS_HASH_FIELDS_TCP_IPV4 0x00000200 >> +#define RSS_HASH_FIELDS_IPV6 0x00000400 >> +#define RSS_HASH_FIELDS_IPV6_EX 0x00000800 >> +#define RSS_HASH_FIELDS_TCP_IPV6 0x00001000 >> +#define RSS_HASH_FIELDS_TCP_IPV6_EX 0x00002000 >> + >> +struct virtio_net_rss_supported_hash{ >> +le32 hash_function; >> +} >> + >> +struct virtio_net_rss { >> +le32 hash_function; >> +le32 hash_function_flags; >> +le32 hash_key_length; >> +le32 indirection_table_length; >> + struct { >> + le32 hash_key[hash_key_length]; >> + le32 indirection_table[indirection_table_length]; >> + } >> +}; >> + >> +#define VIRTIO_NET_SM_CTRL_RSS_GET_SUPPORTED_FUNCTIONS 0 >> +#define VIRTIO_NET_SM_CTRL_RSS_SET 1 >> +\end{lstlisting} >> + >> +If the VIRTIO_NET_F_CTRL_STEERING_MODE is negotiated the driver can >> send control >> +commands using the VIRTIO_NET_CTRL_SM_CONTROL command along with the >> STEERING_MODE_RSS >> +flag for configuring RSS the virtio_net_steering_mode should be filled. >> The >> +\field{steering_mode} field should be filled with the STEERING_MODE_RSS >> flag along >> +with one of the VIRTIO_NET_SM_CTRL_RSS commands in the \field{command} >> field. The >> +\field{rss_conf} field should be used. >> > May be reworded for clarify along the lines: If > theVIRTIO_NET_F_CTRL_STEERING_MODE > feature bit is negotiated, the driver can send steering mode control > command, > VIRTIO_NET_CTRL_SM_CONTROL, with the STEERING_MODE_RSSflag for configuring > RSS provided > it is one of the supported modes. The supported steering modes returned > by device in > response to VIRTIO_NET_CTRL_SM_GET_SUPPORTED_MODES command issued by the > driver. > For configuring particulars of RSS steering mode, the various fields of > virtio_net_steering_mode should be filled by the driver. This includes > \field{steering_mode} with STEERING_MODE_RSS flag along > with one of the VIRTIO_NET_SM_CTRL_RSS commands in the \field{command} > field in addition to union \field{rss_conf} field members. Thanks for the suggestions, I'll rephrase the paragraph based on the above. > > + >> +The class VIRTIO_NET_CTRL_RSS has two commands: >> + >> +\begin{enumerate} >> +\item VIRTIO_NET_SM_CTRL_RSS_GET_SUPPORTED_FUNCTIONS returns the hash >> functions >> + supported by the device to the driver. >> +\item VIRTIO_NET_SM_CTRL_RSS_SET applies the new RSS configuration. The >> command is >> + used by the driver for setting RSS hash function, hash key and >> + indirection table in the device. >> +\end{enumerate} >> + >> +\devicenormative{\subparagraph}{Receive Side Scaling}{Device Types / >> Network Device / Device Operation / Control Virtqueue / Steering mode / >> Receive Side Scaling} >> + >> +The device MUST fill the virtio_net_rss_supported_hash structure with >> the hash >> +functions it supports and return the structure to the driver. One or more >> +flags of the RSS_HASH_FUNCTION flags MUST be used to fill the >> \field{hash_function} >> +field. >> + >> +The device MUST drop all previous RSS configuration upon receiving >> +VIRTIO_NET_SM_CTRL_RSS_SET command. >> + >> +The device MUST set the RSS configuration according to the settings >> provided as >> +follows, once the configuration process is completed the device SHOULD >> apply >> +the hash function to each of the incoming packets with regards to the >> flags in >> +the \field{hash_function_flags} fields and distribute the packets >> through the >> +virqueues using the calculated hash and the indirection table that were >> earlier >> +provided by the driver. >> + >> +Setting RSS configuration >> +\begin{enumerate} >> +\item The driver fills all of the fields and passes them through the >> control >> + queue to the device. >> + >> +\item The device sets the RSS configuration as provided by the driver. >> + >> +\item If the device successfully applied the configuration, on each >> packet >> + received the device MUST calculate the hash for the packet using >> + the fields specified in \field{hash_function_flags} and store it >> in the >> + virtio-net header in the \field{hash} field and the hash fields >> + used in the calculation. >> +\end{enumerate} >> + >> +\drivernormative{\subparagraph}{Receive Side Scaling}{Device Types / >> Network Device / Device Operation / Control Virtqueue / Steering mode / >> Receive Side Scaling} >> + >> +If the driver wants to set RSS hash it should fill the RSS structure >> fields >> +as follows: >> + >> +\begin{itemize} >> +\item The driver SHOULD choose the hash function that SHOULD be used and >> fill >> + it in the \field{hash_function} field along with the appropriate >> flags >> + in the \field{hash_function_flags} field. These flags indicate to >> the >> + device which packet fields MUST be used in the calculation >> process of >> + the hash. >> +\item Once the hash function has been chosen a hash key should also be >> set by >> + the driver in the \field{hash_key} field, the length of the key >> should >> + be stored in the \field{hash_key_length} field. >> +\item Lastly the driver should fill the indirection table array in the >> + \field{indirection_table} field while setting the array length in >> + \field{indirection_table_length}. This structure is used by the >> device >> + for determining in which RX virt queue the packet should be >> placed. >> +\end{itemize} >> +Once the configuration phase is over successfully, the packets SHOULD >> have the >> +\field{hash} field with the hash value that was calculated by the device. >> + >> +Whenever the driver wants to stop performing RSS, it can switch back to >> > Should we say: ..stop performing RSS or any earlier configured steering > mode, Since this section is devoted to RSS I think we should keep this RSS specific. > > +Automatic Steering Mode using the VIRTIO_NET_CTRL_SM_CONTROL command >> along with >> +the STEERING_MODE_AUTO flag. >> + >> \paragraph{Offloads State Configuration}\label{sec:Device Types / >> Network Device / Device Operation / Control Virtqueue / Offloads State >> Configuration} >> If the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is negotiated, the >> driver can >> > > -- Respectfully, *Sameeh Jubran* *Linkedin <https://il.linkedin.com/pub/sameeh-jubran/87/747/a8a>* *Software Engineer @ Daynix <http://www.daynix.com>.*
