[openib-general] QoS RFC - Resend using a friendly mailer

[Sasha Khapyorsky]

Hi Eitan,

Some more comments related to OpenSM.

On 17:53 Tue 30 May     , Eitan Zahavi wrote:
> 
> 9. OpenSM features
> -------------------
> The QoS related functionality to be provided by OpenSM can be split into two 
> main parts:
> 
> 3.1. Fabric Setup
> During fabric initialization the SM should parse the policy and apply its 
> settings to the discovered fabric elements. The following actions should be 
> performed:
> * Parsing of policy
> * Node Group identification. Warning should be provided for each node not 
>   specified but found.
> * SL2VL settings validation should be checked:
>   + A warning will be provided if there are no matching targets for the SL2VL 
>     setting statement. 
>   + An error message will be printed to the log file if an invalid setting is 
>     found. A setting is invalid if it refers to:
>     - Non existing port numbers of the target devices
>     - Unsupported VLs for the target device. In the later case the map to non
>       existing VLs should be replaced to VL15 i.e. packets will be dropped.

Not sure that unsupported VLs mapping to VL15 is best option. Actually
if SL2VL will be specified per port group this may mean that at least in
"generic" case all group members should have similar physical
capabilities or "reliable" part of SLs will be limited by lowest VLCap
in this group (other SLs will be just dropped somewhere).

In current SL2VL mapping implementation we are using such rule to replace
unsupported VLs: (new VL) = (requested VL) % (operational data VLs)
This may have some disadvantage too, but I think it is generally "safer".

Also I guess that by "unsupported VLs" you are referring unsupported or
non-configured VLs.

> * SL2VL setting is to be performed
> * VL Arbitration table settings should be validated according to the following 
>   rules:
>   + A warning will be provided if there are no matching targets for the setting 
>     statement
>   + An error will be provided if the port number exceeds the target ports
>   + An error will be generated if the table length exceeds device capabilities
>   + An warning will be generated if the table quote a VL that is not supported 
>     by the target device

Should there be replacement rule for not supported VLs?

In IBTA spec (v.1, p.190, l.14) is stated that entry with unsupported VL
may be skipped _OR_ "trusted" to other (supported) VL. I think if we will
not care about unsupported replacement there may be hole for
"device/vendor dependent" behavior.

Sasha