[ofa-general] [PATCH 1/3] mcast loopback block

[Ralph Campbell]

On Mon, 2008-06-02 at 21:06 +0300, Olga Shern (Voltaire) wrote:
> 
> 
> On 6/2/08, Ralph Campbell <ralph.campbell at qlogic.com> wrote: 
>         On Mon, 2008-06-02 at 20:52 +0300, Olga Shern (Voltaire)
>         wrote:
>         >
>         >
>         > On 6/2/08, Ralph Campbell <ralph.campbell at qlogic.com> wrote:
>         >         What do you mean by "block loopback"?
>         >         Does this mean a posted send WR for a multicast
>         packet
>         >         that matches the local LID is not sent at all or
>         >         the packet is sent on the wire but not sent to
>         >         the local QP? Or is it something else?
>         >
>         >
>         > It controls the ConnectX HCA multicast packets block
>         loopback
>         > (blck_lb) for self QP. The patch is designed to enable or
>         >
>         > disable blocking of all multicast packets on self QP created
>         on the
>         > ConnectX HCA
>         
>         I understand that the patch enables/disables the bit.
>         You didn't really answer my question which is what does
>         the bit really do. I'm pretty sure it means that multicast
>         packets aren't forwarded to any locally attached QPs
>         but I wanted to be sure that is what it does.
>         
> 
> No, 
> It isn't  disabled  for every QP (by default loopback is enabled),
> when you attach QP to multicast group you can decide to disable  it
> (the decision is done per QP)

So, in other words, if you create a QP with this option and then
attach it to a multicast group and a multicast packet is posted
on the send work request queue of the "disabled" QP, it won't
receive a copy of the packet it sent. If some other QP on the
same HCA is also attached to the same multicast group, it will
receive a copy of the multicast packet.