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=-21.5 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 E297EC2D0E4 for ; Fri, 11 Dec 2020 01:06:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AE4FC23DE3 for ; Fri, 11 Dec 2020 01:06:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394005AbgLKBFB (ORCPT ); Thu, 10 Dec 2020 20:05:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33852 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388215AbgLKBEd (ORCPT ); Thu, 10 Dec 2020 20:04:33 -0500 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 389DFC0613D6 for ; Thu, 10 Dec 2020 17:03:53 -0800 (PST) Received: by mail-pg1-x542.google.com with SMTP id g18so6010605pgk.1 for ; Thu, 10 Dec 2020 17:03:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=gRAABGxDXNyht01AwqCVen+VNx8koj/AyEw1DNWfeno=; b=GuoAZ3c4sxU7UvhZHwNyRUy5ZjQsJCbKDH5620MPq6gLNEzGtVgKY6J+PC7MohqgzW y+1Q0TvAtvzUekzDwER2GDzHor1oQErJ7MVgN+nxBUmuIaOEwIBUflDr0VzphSQQt3YX PwK/mJ2G3Mwj0MP5hyNNnAHt9+pgli9xEXq+Eki13zXSr5GYtZeOLcc1XKDneTPnnmfp RLNGsIfevifvpGpMsQv5pLlBxJOx0nYzN32ryqqLZXHjtsQYe8dSePTsZTVyGXvTk1xY uFT7KyplABRCEzHUmYM0pTjmP93B4ucgR5ick/sab9BhroTIPXbyshNQ196cpr6W3yKw MvZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=gRAABGxDXNyht01AwqCVen+VNx8koj/AyEw1DNWfeno=; b=lvW+yleafHpQD+qiiwePlO40Dr9KYQJeLQSjv69eo0FAYIGGS4zjkJuwvqa5JIFi8k tJfD0jo7d6NXoic9KcWBbaEICKPGF9MjFU3s5IHgf17U2nLnnQlQIIL7QxI3hYoUQTBM V9YpKF0yfVgfuEdMbP/mLJQl95YUvdo0zfBwKDGmHJIpvRE037cFCNg3UnzEV6NnrO1r FDpL/umIghe9WxMgUjhE1HNL9tounGAHYUeHSgUO4hCBK5TP+lKT+FaPryAJ/MgTzVKN uzpcQGT/iYaFLh57HfEeoah5I42uWFEuaB81fdTEE1ObYyFNTxUsGFzrcQ1VvAPPuUgi zhSw== X-Gm-Message-State: AOAM5335/MG5kTpfgPZizmBUmMs5nGIAxy/kayTj2OamR7Xj/1EdO8Nc X+POy8bT0Eh7VQnE9myUzolLus8wYchfaw== X-Google-Smtp-Source: ABdhPJz+WKhv8QQj14gUd83tiDTU+7RfRXK8FIopxaby6kdMc73H/THdo1/M6DGmch6ftnRMeTfqbA== X-Received: by 2002:a62:1506:0:b029:19e:aca2:4ed8 with SMTP id 6-20020a6215060000b029019eaca24ed8mr6425373pfv.27.1607648632566; Thu, 10 Dec 2020 17:03:52 -0800 (PST) Received: from google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) by smtp.gmail.com with ESMTPSA id j8sm8061240pji.1.2020.12.10.17.03.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Dec 2020 17:03:51 -0800 (PST) Date: Thu, 10 Dec 2020 17:03:44 -0800 From: Sean Christopherson To: Kyung Min Park Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, pbonzini@redhat.com, sean.j.christopherson@intel.com, jmattson@google.com, joro@8bytes.org, vkuznets@redhat.com, wanpengli@tencent.com, cathy.zhang@intel.com Subject: Re: [PATCH 2/2] x86: Expose AVX512_FP16 for supported CPUID Message-ID: References: <20201208033441.28207-1-kyung.min.park@intel.com> <20201208033441.28207-3-kyung.min.park@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201208033441.28207-3-kyung.min.park@intel.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Shortlog should use "KVM: x86: ...", and probably s/for/in. It currently reads like the kernel is exposing the flag to KVM for KVM's supported CPUID, e.g.: KVM: x86: Expose AVX512_FP16 in supported CPUID On Mon, Dec 07, 2020, Kyung Min Park wrote: > From: Cathy Zhang > > AVX512_FP16 is supported by Intel processors, like Sapphire Rapids. > It could gain better performance for it's faster compared to FP32 > while meets the precision or magnitude requirement. It's availability > is indicated by CPUID.(EAX=7,ECX=0):EDX[bit 23]. > > Expose it in KVM supported CPUID, then guest could make use of it. For new features like this that don't require additional KVM enabling, it would be nice to explicitly state as much in the changelog, along with a brief explanation of why additional KVM enabling is not necessary. It doesn't have to be much, just something to help people that aren't already familiar with FP16 understand what this patch actually exposes to the guest. E.g. I assume there are new instructions that are available with FP16? > Signed-off-by: Cathy Zhang > Signed-off-by: Kyung Min Park > Acked-by: Dave Hansen > Reviewed-by: Tony Luck > --- > arch/x86/kvm/cpuid.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index e83bfe2daf82..d7707cfc9401 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -416,7 +416,7 @@ void kvm_set_cpu_caps(void) > F(AVX512_4VNNIW) | F(AVX512_4FMAPS) | F(SPEC_CTRL) | > F(SPEC_CTRL_SSBD) | F(ARCH_CAPABILITIES) | F(INTEL_STIBP) | > F(MD_CLEAR) | F(AVX512_VP2INTERSECT) | F(FSRM) | > - F(SERIALIZE) | F(TSXLDTRK) > + F(SERIALIZE) | F(TSXLDTRK) | F(AVX512_FP16) > ); > > /* TSC_ADJUST and ARCH_CAPABILITIES are emulated in software. */ > -- > 2.17.1 >