[openib-general] Re: RFC: e2e credits

[Hal Rosenstock]

On Fri, 2006-03-24 at 07:08, Michael S. Tsirkin wrote:
> Quoting r. Hal Rosenstock <halr at voltaire.com>:
> > 
> > I did some spec reading to find this and found the following which I
> > think makes the current requirement clear:
> > 
> > p.347 line 37 states "HCA receive queues must generate end-to-end
> > credits (except for QPs associated with a SRQ), but TCA receive queues
> > are not required to do so. This appears to be informative text. I first
> > found the following:
> > 
> > p. 348 has the compliances for this for both HCAs and TCAs:
> > 
> > C9-150.2.1: For QPs that are not associated with an SRQ, each HCA re-
> > ceive queue shall generate end-to-end flow control credits. If a QP is
> > associated with an SRQ, the HCA receive queue shall not generate end-to-
> > end flow control credits.
> > 
> > o9-95.2.1: Each TCA receive queue may generate end-to-end credits ex-
> > cept for QPs that are associated with an SRQ. If a TCA supports SRQ, the
> > TCA must not generate End-to-End Flow Control Credits for QPs associ-
> > ated with an SRQ.
> > 
> > C9-151: If a TCA's given receive queue generates End-to-End credits,
> > then the corresponding send queue shall receive and respond to those
> > credits. This is a requirement on each send queue of a CA.
> > 
> > The above informative text also references the CA requirements in
> > chapter 17 and on p. 1026 line 25 there is a row in the table for end to
> > end flow control for RC consistent with the above. p.1028 has the
> > compliances for this.
> 
> I know. You are saying HCA's will never have invalid code in AETH?
> However we have this, towards the end of page 355.
> 
> ----
> 
> "Even a responder which does generate end-to-end credits may choose to send
> the 'invalid' code in the AETH"
> 
> ----
> 
> This seems to imply that HCA (which must generate end-to-end credits)
> may choose to send the 'invalid' code in the AETH?
> 
> What's your take on this?

Isn't it needed for when HCAs talk to TCAs which don't support E2E ?

-- Hal