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,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 A0BDCC433E6 for ; Tue, 14 Jul 2020 19:09:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6690C22AAE for ; Tue, 14 Jul 2020 19:09:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6690C22AAE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0D5058D0005; Tue, 14 Jul 2020 15:09:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 086068D0001; Tue, 14 Jul 2020 15:09:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EDC6F8D0005; Tue, 14 Jul 2020 15:09:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id D56778D0001 for ; Tue, 14 Jul 2020 15:09:48 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 770C4180AD811 for ; Tue, 14 Jul 2020 19:09:48 +0000 (UTC) X-FDA: 77037620856.22.team35_5204a3026ef3 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id 4A0C218038E60 for ; Tue, 14 Jul 2020 19:09:48 +0000 (UTC) X-HE-Tag: team35_5204a3026ef3 X-Filterd-Recvd-Size: 3469 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Tue, 14 Jul 2020 19:09:47 +0000 (UTC) IronPort-SDR: 27CDx0OPjjOhe7jbvnsU5BFXf1UKuu0jFM+hzYfychQCDqt1PIVzx2niYYgNO1QCX/HsRPj1MQ ui6Bdb182Pcg== X-IronPort-AV: E=McAfee;i="6000,8403,9682"; a="149005314" X-IronPort-AV: E=Sophos;i="5.75,352,1589266800"; d="scan'208";a="149005314" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jul 2020 12:09:46 -0700 IronPort-SDR: F5+6TagJ+l1griOYsZtzQkFGRpSQRa2AcrvfdSOx4vFmi7tumHZNFRIJUHlFtNvtasUh0ZpCV3 s3kdDTQFO7MA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,352,1589266800"; d="scan'208";a="285855453" Received: from iweiny-desk2.sc.intel.com ([10.3.52.147]) by orsmga006.jf.intel.com with ESMTP; 14 Jul 2020 12:09:45 -0700 Date: Tue, 14 Jul 2020 12:09:45 -0700 From: Ira Weiny To: Peter Zijlstra 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 Subject: Re: [RFC PATCH 04/15] x86/pks: Preserve the PKRS MSR on context switch Message-ID: <20200714190945.GD3008823@iweiny-DESK2.sc.intel.com> References: <20200714070220.3500839-1-ira.weiny@intel.com> <20200714070220.3500839-5-ira.weiny@intel.com> <20200714082701.GO10769@hirez.programming.kicks-ass.net> <20200714185322.GB3008823@iweiny-DESK2.sc.intel.com> <20200714190539.GG5523@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200714190539.GG5523@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.11.1 (2018-12-01) X-Rspamd-Queue-Id: 4A0C218038E60 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 14, 2020 at 09:05:39PM +0200, Peter Zijlstra wrote: > On Tue, Jul 14, 2020 at 11:53:22AM -0700, Ira Weiny wrote: > > On Tue, Jul 14, 2020 at 10:27:01AM +0200, Peter Zijlstra wrote: > > > On Tue, Jul 14, 2020 at 12:02:09AM -0700, ira.weiny@intel.com wrote: > > > > From: Ira Weiny > > > > > > > > The PKRS MSR is defined as a per-core register. This isolates memory > > > > access by CPU. Unfortunately, the MSR is not preserved by XSAVE. > > > > Therefore, We must preserve the protections for individual tasks even if > > > > they are context switched out and placed on another cpu later. > > > > > > This is a contradiction and utter trainwreck. > > > > I don't understand where there is a contradiction? Perhaps I should have said > > the MSR is not XSAVE managed vs 'preserved'? > > You're stating the MSR is per-*CORE*, and then continue to talk about > per-task state. > > We've had a bunch of MSRs have exactly that problem recently, and it's > not fun. We're not going to do that again. Ah sorry, my mistake yes I meant 'per-logical-processor' like Dave said. I'll update the commit message. Ira