Fwd: Re: [openib-general] static LID computation with TS_HOST_DRIVER
David M. Brean
David.Brean at Sun.COM
Wed Sep 29 08:49:46 PDT 2004
The subnet management state is protected by an M_Key (see section
14.2.4). The M_Key is managed by the SM. The M_Key is not exposed via
the Verbs or through SA queries [the exception being the trusted entity,
but that entity is another SA or higher layer management application -
so let's ignore for this situation.] An endnode implementation should
not allow any back-door mechanism that enables changing the subnet
management state without the M_Key if the port is protected. Note, the
M_Key and protection bits can be in persistent storage and preserved
across port power cycles to eliminate the power-up exposure. So,
without making subnet assumptions/restrictions, there is no reliable way
for an IB client, like the local MAD layer, to specify the LID.
LID assignment is SM policy and the SM may choose to preserve a port's
LID, however, I don't think IB clients should depend on this behavior.
Roland Dreier wrote:
> David> Ok. How does the port inform the SM that it has a
> David> "preferred" LID?
>The port will already have a LID assigned when the SM discovers it.
>My understanding is that the SM is "encouraged" to preserve a port's
>LID if it doesn't conflict with any other LIDs, and this is what we're
> - Roland
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