On Sun, Feb 24, 2019 at 08:59:45PM +0100, Rafael J. Wysocki wrote: > On Fri, Feb 22, 2019 at 7:48 PM Keith Busch <keith.busch@xxxxxxxxx> wrote: > > If I do it the other way around, that's going to make HMEM_REPORTING > > complicated if a non-ACPI implementation wants to report HMEM > > properties. > > But the mitigations that Dave was talking about get in the way, don't they? > > Say there is another Kconfig option,CACHE_MITIGATIONS, to enable them. > Then you want ACPI_HMAT to be set when that it set and you also want > ACPI_HMAT to be set when HMEM_REPORTING and ACPI_NUMA are both set. > > OTOH, you may not want HMEM_REPORTING to be set when CACHE_MITIGATIONS > is set, but that causes ACPI_HMAT to be set and which means that > ACPI_HMAT alone will not be sufficient to determine the > HMEM_REPORTING value. I can't think of when we'd want to suppress reporting these attributes to user space, but I can split HMAT enabling so it doesn't depend on HMEM_REPORTING just in case there really is an in-kernel user that definitely does not want the same attributes exported. > Now, if you prompt for HMEM_REPORTING and make it depend on ACPI_NUMA, > then ACPI_HMAT can be selected by that (regardless of the > CACHE_MITIGATIONS value). > > And if someone wants to use HMEM_REPORTING without ACPI_NUMA, it can > be made depend on whatever new option is there for that non-ACPI > mechanism. > > There might be a problem if someone wanted to enable the alternative > way of HMEM_REPORTING if ACPI_NUMA was set (in which case HMAT would > have to be ignored even if it was present), but in that case there > would need to be an explicit way to choose between HMAT and non-HMAT > anyway. > > In any case, I prefer providers to be selected by consumers and not > the other way around, in case there are multiple consumers for one > provider. Well, the HMEM_REPORTING fundamentally has no dependency on any of these things and I've put some effort into making this part provider agnostic. I will change it if this concern is gating acceptance, but I don't think it's as intuitive for generic interfaces to be the selector for implementation specific providers.
