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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 17F5EC63798 for ; Fri, 20 Nov 2020 05:03:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1C48223AC for ; Fri, 20 Nov 2020 05:03:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="JZ+iZhDr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725821AbgKTFCq (ORCPT ); Fri, 20 Nov 2020 00:02:46 -0500 Received: from mail.kernel.org ([198.145.29.99]:54828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725208AbgKTFCp (ORCPT ); Fri, 20 Nov 2020 00:02:45 -0500 Received: from mail-wr1-f44.google.com (mail-wr1-f44.google.com [209.85.221.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8ACCF223C6 for ; Fri, 20 Nov 2020 05:02:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1605848564; bh=AV4arF6joHpyOzsujwQPuWmRxvPkX+FTXHnctBnhRIw=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=JZ+iZhDrcYtWo1BNYKl29fyEog5Yas44k42jsVLZbSf9eIfnh1ErEmayxLf8rgDf1 Om7oDqRvQrWTLMfqbPw+0NXFWavkt1itwxwHe7YIJlttIVzOtARIuFe9IeG3MXYhS0 46bX+HTejNLbmamlFuGKa8G7eviqVrZ21NHssCMs= Received: by mail-wr1-f44.google.com with SMTP id j7so8739527wrp.3 for ; Thu, 19 Nov 2020 21:02:44 -0800 (PST) X-Gm-Message-State: AOAM5322HhcdPRwZ5Ds2dJfmBo9MAft5KtelKp0kSpShhd66YBqY+kwd KUECTzhpUuGuuSYhRhl1Q88VXIF5qgiKkqfrautkWA== X-Google-Smtp-Source: ABdhPJzLdwTlc0MaXRRiCArrPUVwln9vDm0OGiPBfiIi22SSfbyiOuqhA4ect3jgdRpyPu4nQk7RvVQ6ZX88djfkIrs= X-Received: by 2002:a5d:49ce:: with SMTP id t14mr13468714wrs.75.1605848563021; Thu, 19 Nov 2020 21:02:43 -0800 (PST) MIME-Version: 1.0 References: <20201119233257.2939-1-chang.seok.bae@intel.com> <20201119233257.2939-23-chang.seok.bae@intel.com> In-Reply-To: <20201119233257.2939-23-chang.seok.bae@intel.com> From: Andy Lutomirski Date: Thu, 19 Nov 2020 21:02:26 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 22/22] x86/fpu/xstate: Introduce boot-parameters for control some state component support To: "Chang S. Bae" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andrew Lutomirski , X86 ML , Len Brown , Dave Hansen , "Liu, Jing2" , "Ravi V. Shankar" , LKML , "open list:DOCUMENTATION" Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 19, 2020 at 3:37 PM Chang S. Bae wrote: > > Rename XFEATURE_MASK_USER_SUPPORTED to XFEATURE_MASK_USER_ENABLED to > literally align with new boot-parameters. > > "xstate.disable=0x60000" will disable AMX on a system that has AMX compiled > into XFEATURE_MASK_USER_ENABLED. > > "xstate.enable=0x60000" will enable AMX on a system that does NOT have AMX > compiled into XFEATURE_MASK_USER_ENABLED (assuming the kernel is new enough > to support this feature). > What's the purpose of xstate.enable? I can't really imagine it's useful for AMX. I suppose it could be useful for hypothetical post-AMX features, but that sounds extremely dangerous. Intel has changed its strategy so many times on XSTATE extensibility that I find it quite hard to believe that supporting unknown states is wise.