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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7081DC433FE for ; Thu, 27 Oct 2022 02:28:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233901AbiJ0C2H (ORCPT ); Wed, 26 Oct 2022 22:28:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234127AbiJ0C15 (ORCPT ); Wed, 26 Oct 2022 22:27:57 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B580143A45; Wed, 26 Oct 2022 19:27:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1666837673; x=1698373673; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=afo/CE2nmd8ntlb2SDjykBmeyxC2sXyG6CNK+1/fCLE=; b=kJ72yHXZBaQRPrBgukF2N3RPqQCkV4Pkq7QdsSMTfs2+d8lFtHR4UiUd MpJv95vc/mzrZ9wd5RprxWDOKeHcDEAX7R0l7cx+wqABOomI2u/9uZh1r FJtfBTGIlLBOe5l5dBs3ncRzDkEPkgxpRdd7M4RxHQzhDfXsSITd2dulK 26zYF1Mnbvm0XHRgFhpNJLzoyibtnGNiwq1aQ1lkljCH/KJqDWh66qZUK heFExs+sWpYVpfFlXQB5rs7mPoU3cZUdO3Ap2EiGmFs1eotWCmyKCIgMZ VGukCoc8nUXmo3Xtyu75JgFPULv2dufeyGy2Gzj81gsmLpwXU3hafqm4G A==; X-IronPort-AV: E=McAfee;i="6500,9779,10512"; a="287828482" X-IronPort-AV: E=Sophos;i="5.95,215,1661842800"; d="scan'208";a="287828482" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Oct 2022 19:27:53 -0700 X-IronPort-AV: E=McAfee;i="6500,9779,10512"; a="634732714" X-IronPort-AV: E=Sophos;i="5.95,215,1661842800"; d="scan'208";a="634732714" Received: from jiaxiche-mobl.ccr.corp.intel.com (HELO [10.238.2.23]) ([10.238.2.23]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Oct 2022 19:27:48 -0700 Message-ID: <4b50da57-f4ec-7bd7-b062-b495612868b4@linux.intel.com> Date: Thu, 27 Oct 2022 10:27:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.3.2 Subject: Re: [PATCH 1/6] x86: KVM: Enable CMPccXADD CPUID and expose it to guest To: Borislav Petkov Cc: kvm@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, pbonzini@redhat.com, ndesaulniers@google.com, alexandre.belloni@bootlin.com, peterz@infradead.org, jpoimboe@kernel.org, chang.seok.bae@intel.com, pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com, jmattson@google.com, sandipan.das@amd.com, tony.luck@intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, fenghua.yu@intel.com, keescook@chromium.org, jane.malalane@citrix.com, nathan@kernel.org, linux-kernel@vger.kernel.org, Sean Christopherson References: <20221019084734.3590760-1-jiaxi.chen@linux.intel.com> <20221019084734.3590760-2-jiaxi.chen@linux.intel.com> From: Jiaxi Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/27/2022 1:15 AM, Borislav Petkov wrote: > On Wed, Oct 26, 2022 at 11:40:31AM +0800, Jiaxi Chen wrote: >>> What do you think about moving CPUID_7_1_EAX to be a KVM-only leaf too? AFAICT, >>> KVM passthrough is the only reason the existing features are defined. > > Yap, looking at the patches which added those 2 feature flags upstream, > they don't look like some particular use was the goal but rather to > expose it to guests. Besides, AVX512 apps do their own CPUID detection. > >> Since CPUID_7_1_EAX has only 5 features now, it is a big waste, >> should we move it to KVM-only leaf as Sean suggested. What's your >> opinion about this? > > Yes, pls do. > > And when you do, make sure to undo what > > b302e4b176d0 ("x86/cpufeatures: Enumerate the new AVX512 BFLOAT16 instructions") > > added. > > Thx. > Yes, will do this in v2. Thanks for reminding~ -- Regards, Jiaxi