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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 C0B55C433E7 for ; Thu, 15 Oct 2020 04:18:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7828C2223F for ; Thu, 15 Oct 2020 04:18:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726065AbgJOESK (ORCPT ); Thu, 15 Oct 2020 00:18:10 -0400 Received: from mga12.intel.com ([192.55.52.136]:44018 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725208AbgJOESK (ORCPT ); Thu, 15 Oct 2020 00:18:10 -0400 IronPort-SDR: AD5fzz89jB62x5ocJkZoD8dYWhzJvyNE1u1q1TlVOet6L34xBR36bCUv79JYU682zC/lJf8m2I 4gEUmP1vHd0g== X-IronPort-AV: E=McAfee;i="6000,8403,9774"; a="145561348" X-IronPort-AV: E=Sophos;i="5.77,377,1596524400"; d="scan'208";a="145561348" 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; 14 Oct 2020 21:18:09 -0700 IronPort-SDR: v7spRh8MuASRkdNNr0ZHoNczdFMxX2I1ak7xY7gos/SeU28ARiQ6EMmXTm9vqvcAGZ60oslnd3 9cmkDq9PvUXw== X-IronPort-AV: E=Sophos;i="5.77,377,1596524400"; d="scan'208";a="531100241" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2020 21:18:08 -0700 Date: Wed, 14 Oct 2020 21:18:08 -0700 From: Ira Weiny To: Dave Hansen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra , Dave Hansen , x86@kernel.org, Dan Williams , Andrew Morton , Fenghua Yu , 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 Subject: Re: [PATCH RFC V3 7/9] x86/entry: Preserve PKRS MSR across exceptions Message-ID: <20201015041808.GS2046448@iweiny-DESK2.sc.intel.com> References: <20201009194258.3207172-1-ira.weiny@intel.com> <20201009194258.3207172-8-ira.weiny@intel.com> <6006a4c8-32bd-04ca-95cc-b2736a5cef72@intel.com> <20201015034645.GQ2046448@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On Wed, Oct 14, 2020 at 09:06:44PM -0700, Dave Hansen wrote: > On 10/14/20 8:46 PM, Ira Weiny wrote: > > On Tue, Oct 13, 2020 at 11:52:32AM -0700, Dave Hansen wrote: > >> On 10/9/20 12:42 PM, ira.weiny@intel.com wrote: > >>> @@ -341,6 +341,9 @@ noinstr void irqentry_enter(struct pt_regs *regs, irqentry_state_t *state) > >>> /* Use the combo lockdep/tracing function */ > >>> trace_hardirqs_off(); > >>> instrumentation_end(); > >>> + > >>> +done: > >>> + irq_save_pkrs(state); > >>> } > >> One nit: This saves *and* sets PKRS. It's not obvious from the call > >> here that PKRS is altered at this site. Seems like there could be a > >> better name. > >> > >> Even if we did: > >> > >> irq_save_set_pkrs(state, INIT_VAL); > >> > >> It would probably compile down to the same thing, but be *really* > >> obvious what's going on. > > I suppose that is true. But I think it is odd having a parameter which is the > > same for every call site. > > Well, it depends on what you optimize for. I'm trying to optimize for > the code being understood quickly the first time someone reads it. To > me, that's more important than minimizing the number of function > parameters (which are essentially free). > Agreed. Sorry I was not trying to be confrontational. There is just enough other things which are going to take me time to get right I need to focus on them... :-D Sorry, Ira