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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 1A7EBC433ED for ; Thu, 20 May 2021 00:16:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F23DC610E9 for ; Thu, 20 May 2021 00:16:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229955AbhETASB (ORCPT ); Wed, 19 May 2021 20:18:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34030 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229525AbhETASB (ORCPT ); Wed, 19 May 2021 20:18:01 -0400 Received: from mail-ej1-x636.google.com (mail-ej1-x636.google.com [IPv6:2a00:1450:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D35EC061574 for ; Wed, 19 May 2021 17:16:40 -0700 (PDT) Received: by mail-ej1-x636.google.com with SMTP id et19so15449172ejc.4 for ; Wed, 19 May 2021 17:16:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=wHpPGTix+cKXCrGrbhMazXmP7v5I8Y6OBdgMIdDgvhA=; b=ddjXPOWYeIZbeFYwXcEC63OBolv0Le7Y/3f+AeeQyEff3Km9EwYGmtXpnyXGiu9igM qZK4wsjYojvgPZwHnLDwlZdlcYGTx79Yv6+bNOsDF8HJjnvQmFeUrmzYRiMk2zbaCfGt Cj7CkkD7egpsojx0Ws3boCrt5Tu6dPWB1vwcOaZ7sIGvUabHoWmRKp/wDwMKGvGiP4eH XhHuG9p11+NGXvnzMVC09P1bD9vZFYnaEuwYgkhz1ln6BuHwvZyIEOqK/LXMe80QBs/l MMHrxXy5RNRS6NmHjZ8ctfYyaaoanU3PUTiBtZrXhBcBZAjtATUiWR2bYi51vmgt+Pfq T8dg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=wHpPGTix+cKXCrGrbhMazXmP7v5I8Y6OBdgMIdDgvhA=; b=T2PBHZNa8NgPskS3LLGks/9MclQtIWMaM0Z8E/JTcG1MbHmVOBLMv9YaIehHpRnqVZ ELAKpyJ8p5HOiwHfU/rhqAtOgiI6RKFnt4GZIyChg8Loj33awE9tHrryAEo0TRloDsV2 woT2kxRLv0WtSE23Z93SSGI0ShBxTrmRcRadoEP/3Fm+0eMUXkpYYOXjEaaKiqyjHCGW rn2fTB3I4g6rU5JSi9teDFgXdalS1c9xbTVdh1HeEPOB74A9skvYCNSUQmkWTqJlrN0e 19xzBnAck8jdVzwwyscD+1Rlkr8fknyfl3d1EFcUiO70fOvfz9XCwKIj6DNif9/36HaF gBjA== X-Gm-Message-State: AOAM531YSRcCwVOsgGBZLFeCiQwyMmS2OS1Ah/OOfE3vQgn7n+4NIWjs gVUio0EvynUyrHPJDLXibHK9COz4H1+t9WYD64u/gQ== X-Google-Smtp-Source: ABdhPJy13CyIvUgU0c4/iO5zJrtRsiJO2AdHbEsxqevLYm6s6ozZg/gRZOmI+Nik0P9z467XnR9IsNRPOcsBJjK2qHg= X-Received: by 2002:a17:906:1d56:: with SMTP id o22mr1755770ejh.264.1621469799143; Wed, 19 May 2021 17:16:39 -0700 (PDT) MIME-Version: 1.0 References: <20210419165451.2176200-1-Jonathan.Cameron@huawei.com> <20210419165451.2176200-3-Jonathan.Cameron@huawei.com> <20210506215934.GJ1904484@iweiny-DESK2.sc.intel.com> <20210511175006.00007861@Huawei.com> <20210514094755.00002081@Huawei.com> <20210517094045.00004d58@Huawei.com> <20210518110403.000013e6@Huawei.com> <20210519161156.00003bf9@Huawei.com> <20210519172052.00002124@Huawei.com> <20210519173352.000026fe@Huawei.com> <20210519180057.00002ac3@Huawei.com> <20210519211818.00002acf@Huawei.com> In-Reply-To: From: Dan Williams Date: Wed, 19 May 2021 17:16:28 -0700 Message-ID: Subject: Re: [RFC PATCH v3 2/4] PCI/doe: Add Data Object Exchange support To: Jonathan Cameron Cc: Ira Weiny , linux-cxl@vger.kernel.org, Linux PCI , Bjorn Helgaas , Lorenzo Pieralisi , Ben Widawsky , Chris Browy , Linux ACPI , "Schofield, Alison" , Vishal L Verma , Linuxarm , Fangjian , Greg KH Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, May 19, 2021 at 4:51 PM Dan Williams wrote: [..] > > The short answer is that lock requirement, in the above note, rules > > out safe direct userspace use of the DOE (unless we can tell the kernel > > is not going to ever use it). > > Linux has the mitigation for that situation defined already. It's the > mechanism for /dev/mem and pci-mmap exclusion: disable the driver to > enable unfettered userspace access (modulo kernel-lockdown is > disabled). > Note that when I say "driver" here, it need not necessarily be the cxl_pci driver for the memory expander. For example, DOE functionality could be handled by an aux-bus device+driver where that can be unloaded without taking down the rest of the CXL driver.