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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 30111C433DF for ; Mon, 19 Oct 2020 09:37:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C8D732225F for ; Mon, 19 Oct 2020 09:37:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="UjWOH0rq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727739AbgJSJhl (ORCPT ); Mon, 19 Oct 2020 05:37:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727556AbgJSJhl (ORCPT ); Mon, 19 Oct 2020 05:37:41 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E38C6C0613CE; Mon, 19 Oct 2020 02:37:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=O3B5SDSSGOQ/+MQUdt0Hy/pyKJ8BUU2Uw0eRUC0gQJw=; b=UjWOH0rqHpfO2evvAot8XfZPhm Ujz8nN5NXFhX2X4ST7K3yr0FRVocJcnYRDv/x7ri2cofoF0tNd4LH43/uNrRKlRuD7TzTxbBiCxfy f08AUp6A/Do8cyTspB4hlKZPrmm2mETomhSipdZAEa6fN7de/Z1evQijJAVE/MGG/DxVM2iU4Qn1q FUGEOKLtigWd+T+4WYYGb9bKOVXkDEghzmKrV64OZSbp3a8dondpd2YaqnxT8BjrOR+snVk2sP+AP w4nUUDdb7ykKA7E8PI1XyPVgSG1NlxEHDdKwSNLo4JS+pBVzA5E8S9e3uLAZUr0QXqTZzSQjS9Nvy WFDYp1rg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kURbQ-0003ky-22; Mon, 19 Oct 2020 09:37:16 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B242E3012C3; Mon, 19 Oct 2020 11:37:14 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A127821447780; Mon, 19 Oct 2020 11:37:14 +0200 (CEST) Date: Mon, 19 Oct 2020 11:37:14 +0200 From: Peter Zijlstra To: Ira Weiny Cc: Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Fenghua Yu , x86@kernel.org, Dave Hansen , Dan Williams , 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 Subject: Re: [PATCH RFC V3 4/9] x86/pks: Preserve the PKRS MSR on context switch Message-ID: <20201019093714.GI2628@hirez.programming.kicks-ass.net> References: <20201009194258.3207172-1-ira.weiny@intel.com> <20201009194258.3207172-5-ira.weiny@intel.com> <429789d3-ab5b-49c3-65c3-f0fc30a12516@intel.com> <20201016111226.GN2611@hirez.programming.kicks-ass.net> <20201017051410.GW2046448@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201017051410.GW2046448@iweiny-DESK2.sc.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Oct 16, 2020 at 10:14:10PM -0700, Ira Weiny wrote: > > so it either needs to > > explicitly do so, or have an assertion that preemption is indeed > > disabled. > > However, I don't think I understand clearly. Doesn't [get|put]_cpu_ptr() > handle the preempt_disable() for us? It does. > Is it not sufficient to rely on that? It is. > Dave's comment seems to be the opposite where we need to eliminate preempt > disable before calling write_pkrs(). > > FWIW I think I'm mistaken in my response to Dave regarding the > preempt_disable() in pks_update_protection(). Dave's concern is that we're calling with with preemption already disabled so disabling it again is superfluous.