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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 315C2C07E96 for ; Thu, 8 Jul 2021 14:41:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 037B761629 for ; Thu, 8 Jul 2021 14:41:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232035AbhGHOoC (ORCPT ); Thu, 8 Jul 2021 10:44:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28195 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231958AbhGHOoB (ORCPT ); Thu, 8 Jul 2021 10:44:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1625755279; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MVHdtokfwVvo9NLtbFn0ekZdo09a+Ervl/zkT6BQW3c=; b=dhivwEDhBtkDCQmqGfgHR0uXn0EM0Wl/0Q72/319znYM7TqcCCt/M2ukpe9ShCwkNgCeUx rwFlSqxppH7mGhsS3XweREDvbaZhqWRsDI1VvXwydMsleN7nfoCmDeILh243Ixeav5kMKb X6bFOPg/g2TucYK6PXPTKc8uTwUU1/8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-275-f2NipTGrOE2JkhbqiqCatA-1; Thu, 08 Jul 2021 10:41:16 -0400 X-MC-Unique: f2NipTGrOE2JkhbqiqCatA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 76EBC18414A0; Thu, 8 Jul 2021 14:41:14 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-115-5.ams2.redhat.com [10.36.115.5]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C4B3510023AB; Thu, 8 Jul 2021 14:41:11 +0000 (UTC) From: Florian Weimer To: Dave Hansen Cc: libc-alpha@sourceware.org, linux-api@vger.kernel.org, x86@kernel.org, linux-arch@vger.kernel.org, "H.J. Lu" , linux-kernel@vger.kernel.org Subject: Re: x86 CPU features detection for applications (and AMX) References: <87tulo39ms.fsf@oldenburg.str.redhat.com> <878s2hz6g3.fsf@oldenburg.str.redhat.com> <87sg0oswqn.fsf@oldenburg.str.redhat.com> Date: Thu, 08 Jul 2021 16:41:09 +0200 In-Reply-To: (Dave Hansen's message of "Thu, 8 Jul 2021 07:36:44 -0700") Message-ID: <87lf6gswai.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org * Dave Hansen: > That's kinda my whole point. > > These *MUST* be curated to be meaningful. Right now, someone just > dumped a set of CPUID bits into the documentation. > > The interface really needs *three* modes: > > 1. Yes, the CPU/OS supports this feature > 2. No, the CPU/OS doesn't support this feature > 3. Hell if I know, never heard of this feature > > The interface really conflates 2 and 3. To me, that makes it > fundamentally flawed. That's an interesing point. 3 looks potentially more useful than the feature/usable distinction to me. The recent RTM change suggests that there are more states, but we probably can't do much about such soft-disable changes. Thanks, Florian