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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 8E01EC43457 for ; Thu, 15 Oct 2020 04:06:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4654C221FF for ; Thu, 15 Oct 2020 04:06:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728776AbgJOEGq (ORCPT ); Thu, 15 Oct 2020 00:06:46 -0400 Received: from mga14.intel.com ([192.55.52.115]:54961 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725208AbgJOEGq (ORCPT ); Thu, 15 Oct 2020 00:06:46 -0400 IronPort-SDR: f04DFpzhMv70t7ZqZ4PDbE+A+GFHOYt+aC8YqDCijkdbfzLyFv+qdxR03jEHtL1CAX4Nfim4D6 PpMPlaV8aVng== X-IronPort-AV: E=McAfee;i="6000,8403,9774"; a="165475102" X-IronPort-AV: E=Sophos;i="5.77,377,1596524400"; d="scan'208";a="165475102" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2020 21:06:45 -0700 IronPort-SDR: 8llCNNVFg/pwnYalAcGap2jzG4kRd1VH03d73DJ/rVUOvJu5WRBvRZXQYNPfk6mOkMTy603tWS seE+lT/OxDKQ== X-IronPort-AV: E=Sophos;i="5.77,377,1596524400"; d="scan'208";a="357582709" Received: from bepietra-mobl.amr.corp.intel.com (HELO [10.209.69.215]) ([10.209.69.215]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Oct 2020 21:06:45 -0700 Subject: Re: [PATCH RFC V3 7/9] x86/entry: Preserve PKRS MSR across exceptions To: Ira Weiny 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 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> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201015034645.GQ2046448@iweiny-DESK2.sc.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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).