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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 7A158C433E0 for ; Fri, 17 Jul 2020 22:36:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 47B6A2074B for ; Fri, 17 Jul 2020 22:36:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726528AbgGQWgS (ORCPT ); Fri, 17 Jul 2020 18:36:18 -0400 Received: from mga12.intel.com ([192.55.52.136]:4983 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726205AbgGQWgR (ORCPT ); Fri, 17 Jul 2020 18:36:17 -0400 IronPort-SDR: YbLsF2JeEdlsLkjOuUX2gIzt/G6IxOzNdQGY9E7Njv12agqD/D/EOVlA97cAuXX0IpMQ7dOH86 auDLC3VV1+Bg== X-IronPort-AV: E=McAfee;i="6000,8403,9685"; a="129253938" X-IronPort-AV: E=Sophos;i="5.75,364,1589266800"; d="scan'208";a="129253938" 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/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2020 15:36:16 -0700 IronPort-SDR: Owd/p5Lk3lNRQK/QkBIfPnFgbLhOUBHjpWSYg9BSixv1oMeGGl/BwfcHsn5Xbt4DSZLAAdF7O9 Wwi43E+a+Fhg== X-IronPort-AV: E=Sophos;i="5.75,364,1589266800"; d="scan'208";a="461003024" Received: from pcramer-mobl1.amr.corp.intel.com (HELO [10.255.6.238]) ([10.255.6.238]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Jul 2020 15:36:13 -0700 Subject: Re: [PATCH RFC V2 02/17] x86/fpu: Refactor arch_set_user_pkey_access() for PKS support To: Peter Zijlstra , ira.weiny@intel.com Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Fenghua Yu , x86@kernel.org, Dave Hansen , Dan Williams , Vishal Verma , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20200717072056.73134-1-ira.weiny@intel.com> <20200717072056.73134-3-ira.weiny@intel.com> <20200717085442.GX10769@hirez.programming.kicks-ass.net> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200717085442.GX10769@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 7/17/20 1:54 AM, Peter Zijlstra wrote: > This is unbelievable junk... Ouch! This is from the original user pkeys implementation. > How about something like: > > u32 update_pkey_reg(u32 pk_reg, int pkey, unsigned int flags) > { > int pkey_shift = pkey * PKR_BITS_PER_PKEY; > > pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift); > > if (flags & PKEY_DISABLE_ACCESS) > pk_reg |= PKR_AD_BIT << pkey_shift; > if (flags & PKEY_DISABLE_WRITE) > pk_reg |= PKR_WD_BIT << pkey_shift; > > return pk_reg; > } > > Then we at least have a little clue wtf the thing does.. Yes I started > with a rename and then got annoyed at the implementation too. That's fine, if some comments get added. It looks correct to me but probably compiles down to pretty much the same thing as what was there. FWIW, I prefer the explicit masking off of two bit values to implicit masking off with a mask generated from PKR_BITS_PER_PKEY. It's certainly more compact, but I usually don't fret over the lines of code.