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I recall Reinette proposed reporting the number of groups which >>>>> can be assigned separately from counters which can be assigned. >>>> >>>> More context may be needed here. Currently, num_mbm_cntrs indicates the >>>> number of counters available per domain, which is 32. >>>> >>>> At the moment, we can assign 2 counters to each group, meaning each RMID >>>> can be associated with 2 hardware counters. In theory, it's possible to >>>> assign all 32 hardware counters to a group—allowing one RMID to be linked >>>> with up to 32 counters. However, we currently lack the interface to >>>> support that level of assignment. >>>> >>>> For now, the plan is to support basic assignment and expand functionality >>>> later once we have the necessary data structure and requirements. >>> >>> Looks like some requirements did not make it into this implementation. >>> Do you recall the discussion that resulted in you writing [2]? Looks like >>> there is a question to Peter in there on how to determine how many "counters" >>> are available in soft-ABMC. I interpreted [3] at that time to mean that this >>> information would be available in a future AMD publication. >> >> We already have a method to determine the number of counters in soft-ABMC >> mode, which Peter has addressed [4]. >> >> [4] >> https://lore.kernel.org/lkml/20250203132642.2746754-1-peternewman@google.com/ >> >> This appears to be more of a workaround, and I doubt it will be included >> in any official AMD documentation. Additionally, the long-term direction >> is moving towards ABMC. >> >> I don’t believe this workaround needs to be part of the current series. It >> can be added later when soft-ABMC is implemented. > > Agreed. What about the plans described in [2]? (Thanks to Peter for > catching this!). > > It is important to keep track of requirements while working on a feature to > ensure that the implementation supports the planned use cases. Re-reading that > thread it is not clear to me how soft-ABMC's per-group assignment would look. > Could you please share how you see it progress from this implementation? > This includes the single event vs. multiple event assignment. I would like to > highlight that this is not a request for this to be supported in this implementation > but there needs to be a plan for how this can be supported on top of interfaces > established by this work. > Here’s my current understanding of soft-ABMC. Peter may have a more in-depth perspective on this. Soft-ABMC: a. num_mbm_cntrs: This is a software-defined limit based on the number of active RMIDs that can be supported. The value can be obtained using the code referenced in [4]. b. Assignments: No hardware configuration is required. We simply need to ensure that no more than num_mbm_cntrs RMIDs are active at any given time. c. Configuration: Controlled via /info/L3_MON/mbm_total_bytes_config and mbm_local_bytes_config. d. Events: Only two events can be assigned(local and total). ABMC: a. num_mbm_cntrs: This is defined by the hardware. b. Assignments: Requires special MSR writes to assign counters. c. Configuration: Comes from /info/L3_MON/counter_configs/. d. Events: More than two events can be assigned to a group (currently up to 2). Commonalities: a. Assignments can be either exclusive or shared in both these modes. Given these, I believe we can easily accommodate soft-ABMC in this interface. >>> >>> [2] https://lore.kernel.org/lkml/afb99efe-0de2-f7ad-d0b8-f2a0ea998efd@amd.com/ >>> [3] https://lore.kernel.org/lkml/CALPaoCg3KpF94g2MEmfP_Ro2mQZYFA8sKVkmb+7isotKNgdY9A@mail.gmail.com/ >> > >