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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_MUTT 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 EDC4BC31E5E for ; Wed, 19 Jun 2019 17:31:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C08F82147A for ; Wed, 19 Jun 2019 17:31:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="Hk0wWDkG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730136AbfFSRbu (ORCPT ); Wed, 19 Jun 2019 13:31:50 -0400 Received: from mail.skyhub.de ([5.9.137.197]:39066 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726197AbfFSRbu (ORCPT ); Wed, 19 Jun 2019 13:31:50 -0400 Received: from zn.tnic (p200300EC2F109900C181231BF4D53555.dip0.t-ipconnect.de [IPv6:2003:ec:2f10:9900:c181:231b:f4d5:3555]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 862011EC066F; Wed, 19 Jun 2019 19:31:48 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1560965508; 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: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=wm6LlMFx4LPsbw3x7ZJ1QJ9Kv8m+cwMMvl4Y9Skn8fo=; b=Hk0wWDkGu8v73FVKv9YuWMwaZttwXeqwCRap0W+Rk0w3rqq104msfhtdjJvgPereHfoYCv rrC6TgwujQd7HUBT7b2me1ZaoaB/v69OPNrNAX5X+zuoFXhmbspogUsKkvviUhoaIxekT/ VJtu98SigligZCeJECAThiQ39wrmkpw= Date: Wed, 19 Jun 2019 19:31:40 +0200 From: Borislav Petkov To: Fenghua Yu Cc: Thomas Gleixner , Ingo Molnar , H Peter Anvin , Christopherson Sean J , Paolo Bonzini , Radim Krcmar , Ravi V Shankar , linux-kernel , x86 Subject: Re: [PATCH v2 2/2] x86/cpufeatures: Enumerate new AVX512 BFLOAT16 instructions Message-ID: <20190619173140.GH9574@zn.tnic> References: <1560794416-217638-1-git-send-email-fenghua.yu@intel.com> <1560794416-217638-3-git-send-email-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1560794416-217638-3-git-send-email-fenghua.yu@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 17, 2019 at 11:00:16AM -0700, Fenghua Yu wrote: > AVX512 Vector Neural Network Instructions (VNNI) in Intel Deep Learning > Boost support BFLOAT16 format (BF16). That sentence is a mouthful and I have no clue what it means. Marketing junk? If so, either rewrite it for mere mortals or kill it. > BF16 is a short version of FP32 FP32? Please write out. > and has several advantages over FP16. Ditto. > BF16 offers more than enough range for > deep learning training tasks and doesn't need to handle hardware exception > as this is a performance optimization. FP32 accumulation after the > multiply is essential to achieve sufficient numerical behavior on an > application level. > > AVX512 BFLOAT16 instructions can be enumerated by: > CPUID.7.1:EAX[bit 5] AVX512_BF16 > > Use word 12, which is empty now, to hold features in CPUID.7.1:EAX > including AVX512_BF16. ... because that leaf is features only, right? > Leaf CPUID_DUMMY is renamed as CPUID_7_1_EAX. That's obvious from the patch, ain't it? > Detailed information of the CPUID bit and AVX512 BFLOAT16 instructions > can be found in the latest Intel Architecture Instruction Set Extensions > and Future Features Programming Reference. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.