From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Busch Subject: Re: [PATCHv6 07/10] acpi/hmat: Register processor domain to its memory Date: Mon, 25 Feb 2019 09:51:18 -0700 Message-ID: <20190225165118.GK10237@localhost.localdomain> References: <20190214171017.9362-1-keith.busch@intel.com> <20190214171017.9362-8-keith.busch@intel.com> <20190222184831.GF10237@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Linux Kernel Mailing List , ACPI Devel Maling List , Linux Memory Management List , Linux API , Greg Kroah-Hartman , Dave Hansen , Dan Williams List-Id: linux-api@vger.kernel.org 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 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.