From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2ECCC43441 for ; Tue, 27 Nov 2018 10:15:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C9692086B for ; Tue, 27 Nov 2018 10:15:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C9692086B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730498AbeK0VNE (ORCPT ); Tue, 27 Nov 2018 16:13:04 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:60680 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726405AbeK0VNE (ORCPT ); Tue, 27 Nov 2018 16:13:04 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6235C3563; Tue, 27 Nov 2018 02:15:39 -0800 (PST) Received: from [10.1.196.73] (unknown [10.1.196.73]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 07C833F575; Tue, 27 Nov 2018 02:15:37 -0800 (PST) Subject: Re: [PATCH 0/7] ACPI HMAT memory sysfs representation To: Dan Williams , Dave Hansen Cc: Keith Busch , Linux Kernel Mailing List , Linux ACPI , Linux MM , Greg KH , "Rafael J. Wysocki" References: <20181114224902.12082-1-keith.busch@intel.com> <1ed406b2-b85f-8e02-1df0-7c39aa21eca9@arm.com> <4ea6e80f-80ba-6992-8aa0-5c2d88996af7@intel.com> <9015e51a-3584-7bb2-cc5e-25b0ec8e5494@intel.com> From: Anshuman Khandual Message-ID: <325d0e69-053a-ae9c-eede-7cdf28b1dbd6@arm.com> Date: Tue, 27 Nov 2018 15:45:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/26/2018 11:38 PM, Dan Williams wrote: > On Mon, Nov 26, 2018 at 8:42 AM Dave Hansen wrote: >> >> On 11/23/18 1:13 PM, Dan Williams wrote: >>>> A new system call makes total sense to me. I have the same concern >>>> about the completeness of what's exposed in sysfs, I just don't see a >>>> _route_ to completeness with sysfs itself. Thus, the minimalist >>>> approach as a first step. >>> Outside of platform-firmware-id to Linux-numa-node-id what other >>> userspace API infrastructure does the kernel need to provide? It seems >>> userspace enumeration of memory attributes is fully enabled once the >>> firmware-to-Linux identification is established. >> >> It would be nice not to have each app need to know about each specific >> platform's firmware. > > The app wouldn't need to know if it uses a common library. Whether the > library calls into the kernel or not is an implementation detail. If > it is information that only the app cares about and the kernel does > not consume, why have a syscall? If we just care about platform-firmware-id <--> Linux-numa-node-id mapping and fetching memory attribute from the platform (and hiding implementation details in a library) then the following interface should be sufficient. /sys/devices/system/node/nodeX/platform_id But as the series proposes (and rightly so) kernel needs to start providing ABI interfaces for memory attributes instead of hiding them in libraries.