On Thu, Oct 15, 2015 at 9:55 PM, Yishai Hadas <yishaih@xxxxxxxxxxxxxxxxxx> wrote: > On 10/15/2015 6:17 PM, Parav Pandit wrote: >> >> On Thu, Oct 15, 2015 at 7:42 PM, Yishai Hadas >> <yishaih@xxxxxxxxxxxxxxxxxx> wrote: >>> >>> On 10/15/2015 12:13 PM, Parav Pandit wrote: >>>> >>>> >>>> Just curious, why does WQ need to be bind to PD? >>>> Isn't ucontext sufficient? >>>> Or because kcontext doesn't exist, PD serves that role? >>>> Or Is this just manifestation of how hardware behave? >>> >>> >>> >>> PD is an attribute of a work queue (i.e. send/receive queue), it's used >>> by >>> the hardware for security validation before scattering to a memory >>> region. >>> For that, an external WQ object needs a PD, letting the >>> hardware makes that validation. >>> >>>> Since you mentioned, "QP can be configured to use "external" WQ >>>> object", it might be worth to reuse the WQ across multiple QPs of >>>> different PD? >>> >>> >>> >>> Correct, external WQ can be used across multiple QPs, in that case its PD >>> is >>> used by the hardware for security validation when it accesses to the MR, >>> in >>> that case the QP's PD is not in use. >>> >> I think I get it, just confirming with below example. > > > . > >> So I think below is possible. >> WQ_A having PD=1. >> QP_A having PD=2 bound to WQ_A. >> QP_B having PD=3 bound to WQ_A. >> MR_X having PD=2. >> And checks are done between MR and QP. > > No, please follow above description, in that case PD=1 of WQ_A is used for > the checks. > This appears to me a manifestation of hardware implementation surfacing the verb layer. There may be nothing wrong in it, but worth to know how to actually do verb programming. If there is stateless WQ being used by multiple QPs in multiplexed way, it should be able to multiplex between QP's of different PD as well. Otherwise for every PD being created, there will have be one WQ needed to service all the QPs belonging to that PD. >> In other use case, >> MR is not at all used. (only physical addresses are used) >> WQ_A having PD=1. >> QP_A having PD=2 bound to WQ_A. >> QP_B having PD=3 bound to WQ_A. >> >> WQ entries fail as MR is not associated and QP are bound to different >> PD than the PD of WQ_A. >> Because at QP bound time with WQ, its unknown whether it will use MR >> or not in the WQE at run time. >> Right? > > > In case there is MR for physical addresses it has a PD and the WQ's PD is > used, in case there is no MR the PD is not applicable. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
