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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 95AF2C43144 for ; Fri, 29 Jun 2018 14:56:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 580A12801A for ; Fri, 29 Jun 2018 14:56:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 580A12801A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755471AbeF2O4r (ORCPT ); Fri, 29 Jun 2018 10:56:47 -0400 Received: from mga12.intel.com ([192.55.52.136]:27776 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751234AbeF2O4p (ORCPT ); Fri, 29 Jun 2018 10:56:45 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jun 2018 07:56:45 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,285,1526367600"; d="scan'208";a="236631778" Received: from unknown (HELO [10.254.106.50]) ([10.254.106.50]) by orsmga005.jf.intel.com with ESMTP; 29 Jun 2018 07:56:40 -0700 Subject: Re: [PATCH v2 1/4] x86/split_lock: Enumerate #AC exception for split locked access feature To: Fenghua Yu , Thomas Gleixner , Ingo Molnar , H Peter Anvin References: <1530282807-66555-1-git-send-email-fenghua.yu@intel.com> <1530282807-66555-2-git-send-email-fenghua.yu@intel.com> Cc: Ashok Raj , Alan Cox , Peter Zijlstra , Rafael Wysocki , Tony Luck , Ravi V Shankar , linux-kernel , x86 From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <1530282807-66555-2-git-send-email-fenghua.yu@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/29/2018 07:33 AM, Fenghua Yu wrote: > +/* Detect feature of #AC for split lock by probing bit 29 in MSR_TEST_CTL. */ > +void detect_ac_split_lock(void) > +{ > + u64 val, orig_val; > + int ret; > + > + /* Attempt to read the MSR. If the MSR doesn't exist, reading fails. */ > + ret = rdmsrl_safe(MSR_TEST_CTL, &val); > + if (ret) > + return; This is a bit fast and loose with how the feature is detected, which might be OK, but can we call out why we are doing this, please? Is this MSR not really model-specific? Is it OK to go poking at it on all x86 variants? Or, do we at _least_ need a check for Intel cpus in here?