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=-2.3 required=3.0 tests=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 AB0BDC31E46 for ; Wed, 12 Jun 2019 03:42:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8388020874 for ; Wed, 12 Jun 2019 03:42:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729343AbfFLDmX (ORCPT ); Tue, 11 Jun 2019 23:42:23 -0400 Received: from mga05.intel.com ([192.55.52.43]:47176 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726568AbfFLDmX (ORCPT ); Tue, 11 Jun 2019 23:42:23 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Jun 2019 20:42:22 -0700 X-ExtLoop1: 1 Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by orsmga005.jf.intel.com with ESMTP; 11 Jun 2019 20:42:20 -0700 Date: Tue, 11 Jun 2019 20:32:59 -0700 From: Fenghua Yu To: Borislav Petkov Cc: Thomas Gleixner , Ingo Molnar , H Peter Anvin , Ravi V Shankar , linux-kernel , x86 Subject: Re: [RFC PATCH] x86/cpufeatures: Enumerate new AVX512 bfloat16 instructions Message-ID: <20190612033259.GE180343@romley-ivt3.sc.intel.com> References: <1560186158-174788-1-git-send-email-fenghua.yu@intel.com> <20190610192026.GI5488@zn.tnic> <20190611181920.GC180343@romley-ivt3.sc.intel.com> <20190611194701.GJ31772@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190611194701.GJ31772@zn.tnic> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 11, 2019 at 09:47:02PM +0200, Borislav Petkov wrote: > On Tue, Jun 11, 2019 at 11:19:20AM -0700, Fenghua Yu wrote: > > So can I re-organize word 11 and 12 as follows? > > > > 1. Change word 11 to host scattered features. > > 2. Move the previos features in word 11 and word 12 to word 11: > > /* > > * Extended auxiliary flags: Linux defined - For features scattered in various > > * CPUID levels and sub-leaves like CPUID level 7 and sub-leaf 1, etc, word 19. > > */ > > #define X86_FEATURE_CQM_LLC (11*32+ 0) /* LLC QoS if 1 */ > > #define X86_FEATURE_CQM_OCCUP_LLC (11*32+ 1) /* LLC occupancy monitoring */ > > #define X86_FEATURE_CQM_MBM_TOTAL (11*32+ 2) /* LLC Total MBM monitoring */ > > #define X86_FEATURE_CQM_MBM_LOCAL (11*32+ 3) /* LLC Local MBM monitoring */ > > Yap. > > > 3. Change word 12 to host CPUID.(EAX=7,ECX=1):EAX: > > /* Intel-defined CPU features, CPUID level 0x7:1 (EAX), word 12 */ > > #define X86_FEATURE_AVX512_BF16 (12*32+ 0) /* BFLOAT16 instructions */ > > This needs to be (12*32+ 5) if word 12 is going to map leaf > CPUID.(EAX=7,ECX=1):EAX. > > At least judging from the arch extensions doc which lists EAX as: > > Bits 04-00: Reserved. > Bit 05: AVX512_BF16. Vector Neural Network Instructions supporting BFLOAT16 inputs and conversion instructions from IEEE single precision. > Bits 31-06: Reserved. > > > 4. Do other necessary changes to match the new word 11 and word 12. > > But split in two patches: first does steps 1+2, second patch adds the > new leaf to word 12. Currently KVM doesn't simulate scattered features (the ones in CPUID_LNX_* in cpuid_leafs) as reverse_cpuid[] doesn't contain CPUID_LNX_*. After the X86_FEATURES_CQM_* features are changed to scattered features, they will not be simulated by KVM any more as CPUID_F_0_EDX and CPUID_F_1_EDX are removed. Should patch #1 simulate X86_FEATURE_CQM_* in KVM? Or let KVM guys handle the scattered features? Thanks. -Fenghua