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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BCC9AC433E1 for ; Fri, 26 Mar 2021 15:28:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F3A861A2D for ; Fri, 26 Mar 2021 15:28:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230294AbhCZP1r (ORCPT ); Fri, 26 Mar 2021 11:27:47 -0400 Received: from mail-ej1-f42.google.com ([209.85.218.42]:33342 "EHLO mail-ej1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230196AbhCZP1d (ORCPT ); Fri, 26 Mar 2021 11:27:33 -0400 Received: by mail-ej1-f42.google.com with SMTP id k10so9070682ejg.0; Fri, 26 Mar 2021 08:27:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CsvTmaNAD+JZrfh5r3rTSTh1rpmcrxqU66s7Dv3Gkbc=; b=n6rfuhxBOr6U36vv91n2Iwiz0iL+xDyXds6Z+NczzAdx96UlVIoVf7viSuXZGW+Z6d D7am5fTfCqRJinkAlegfRDwTw5uoxuKBgQkVrXd2IuQQXW6Spa7Tlk7PLRAvx0e2dfYW Zw7IpT4o7N54RmIP93C6be4oQxV539ihK8J2AqQOoE5ZAJ6ywAPgBKExakfMJWCEd3o7 oQyRI2BWAXIesbPW+3Ap/Nz7Po5Ite/gj2d8G/5tkrI3Nnti76fRDT6CNXbtL0BA0uyJ 6BG8sJrpW/qcSpzGj53iTOW5SN/t4TtF3+IiE06cdh+nvbhdbD+Fi6p/DUI6YPwVW0y7 1jow== X-Gm-Message-State: AOAM532syNrsBvijHVPSMwXKRQLKJf30cAer7PZdWV9XUi8uc3YE1xsv TINlM7sQZw30bhTv6MpYHe5kqLjMHDb1GN9EMiujA1wt X-Google-Smtp-Source: ABdhPJyFlw7rGrbUJFQ4KQwktBppReA8rH3lAxc1L6Lop8M+D8rVfU1AuaGVizQy1Tm1K2rwqAwvBOS8Mf3XBUZqRss= X-Received: by 2002:a17:906:340f:: with SMTP id c15mr2779781ejb.317.1616772452060; Fri, 26 Mar 2021 08:27:32 -0700 (PDT) MIME-Version: 1.0 References: <20210221185637.19281-1-chang.seok.bae@intel.com> <20210221185637.19281-23-chang.seok.bae@intel.com> <871rc9bl3v.fsf@nanos.tec.linutronix.de> In-Reply-To: From: Len Brown Date: Fri, 26 Mar 2021 11:27:20 -0400 Message-ID: Subject: Re: [PATCH v4 22/22] x86/fpu/xstate: Introduce boot-parameters to control state component support To: Dave Hansen Cc: Thomas Gleixner , "Chang S. Bae" , Borislav Petkov , Andy Lutomirski , Ingo Molnar , X86 ML , "Brown, Len" , "Liu, Jing2" , "Ravi V. Shankar" , Linux Kernel Mailing List , Linux Documentation List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 25, 2021 at 7:10 PM Dave Hansen wrote: > > On 3/25/21 3:59 PM, Len Brown wrote: > > We call AMX a "simple state feature" -- it actually requires NO KERNEL ENABLING > > above the generic state save/restore to fully support userspace AMX > > applications. > > > > While not all ISA extensions can be simple state features, we do expect > > future features to share this trait, and so we want to be sure that it is simple > > to update the kernel to turn those features on (and when necessary, off). > > From some IRC chats with Thomaas and Andy, I think it's safe to say that > they're not comfortable blindly enabling even our "simple features". I > think we're going to need at least some additional architecture to get > us to a point where everyone will be comfortable. Hi Dave, There is no code in this patch series, including patch 22, that enables an unvalidated feature by default. Yes, I fully accept that patch 22 allows a user to enable something that a distro didn't validate. If there is a new requirement that the kernel cmdline not allow anything that a distro didn't explicitly validate, then about 99.9% of the kernel cmdline options that exist today would need to be removed. Does such a requirement exist, or does it not? thanks, -Len