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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 23C84C433E3 for ; Sat, 11 Jul 2020 19:53:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EFDB72077D for ; Sat, 11 Jul 2020 19:53:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594497233; bh=Z16Tvyu00GM8lWPjZaVxUYQVl8q4upyC4+JAo11HVT4=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=WjW/vPKJqxCdvoUWPms4dlGmk5aU8wbR41DoZc5+JNxrQukl5LMDiDgf8FyRNdx+t CtnSxVR4wJuab64xz0T0uquXKHFtN7ryXNBRLgdrTEWzPOtRrJH2gg5IVFhJJ4V9Bh hWcswhw9hK6aRhL5EDr4zFBITD8Q7D2iTNuCsCQs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726729AbgGKTxt (ORCPT ); Sat, 11 Jul 2020 15:53:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:51866 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726606AbgGKTxs (ORCPT ); Sat, 11 Jul 2020 15:53:48 -0400 Received: from localhost (mobile-166-175-191-139.mycingular.net [166.175.191.139]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 939A820725; Sat, 11 Jul 2020 19:53:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594497228; bh=Z16Tvyu00GM8lWPjZaVxUYQVl8q4upyC4+JAo11HVT4=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=j5yQ/CohDw63QZlCRPNpB3igj8YUwmWz54kQmR+NLDemFBfMmRRyj9/fuFXIS/v5l 3+MtbbkCOKqOka1dDKyYWRtf6hATIydJPL9bZqOY/LWXNw0x+EsedbDrP/UmzD93DF 3kZBjfdZw4jfkVJfgeBp42Hfh+z3ro3SuIb9JwjA= Date: Sat, 11 Jul 2020 14:53:46 -0500 From: Bjorn Helgaas To: Rajat Jain Cc: "Raj, Ashok" , David Woodhouse , Lu Baolu , Joerg Roedel , Bjorn Helgaas , "Rafael J. Wysocki" , Len Brown , "open list:AMD IOMMU (AMD-VI)" , Linux Kernel Mailing List , linux-pci , ACPI Devel Maling List , "Krishnakumar, Lalithambika" , Mika Westerberg , Jean-Philippe Brucker , Prashant Malani , Benson Leung , Todd Broch , Alex Levin , Mattias Nissler , Rajat Jain , Bernie Keany , Aaron Durbin , Diego Rivas , Duncan Laurie , Furquan Shaikh , Jesse Barnes , Christian Kellner , Alex Williamson , Greg Kroah-Hartman , Oliver O'Halloran , Saravana Kannan , Suzuki K Poulose , Arnd Bergmann , Heikki Krogerus Subject: Re: [PATCH v4 4/4] PCI/ACS: Enable PCI_ACS_TB for untrusted/external-facing devices Message-ID: <20200711195346.GA132330@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Fri, Jul 10, 2020 at 03:53:59PM -0700, Rajat Jain wrote: > On Fri, Jul 10, 2020 at 2:29 PM Raj, Ashok wrote: > > On Fri, Jul 10, 2020 at 03:29:22PM -0500, Bjorn Helgaas wrote: > > > On Tue, Jul 07, 2020 at 03:46:04PM -0700, Rajat Jain wrote: > > > > When enabling ACS, enable translation blocking for external facing ports > > > > and untrusted devices. > > > > > > > > Signed-off-by: Rajat Jain > > > > --- > > > > v4: Add braces to avoid warning from kernel robot > > > > print warning for only external-facing devices. > > > > v3: print warning if ACS_TB not supported on external-facing/untrusted ports. > > > > Minor code comments fixes. > > > > v2: Commit log change > > > > > > > > drivers/pci/pci.c | 8 ++++++++ > > > > drivers/pci/quirks.c | 15 +++++++++++++++ > > > > 2 files changed, 23 insertions(+) > > > > > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > > > index 73a8627822140..a5a6bea7af7ce 100644 > > > > --- a/drivers/pci/pci.c > > > > +++ b/drivers/pci/pci.c > > > > @@ -876,6 +876,14 @@ static void pci_std_enable_acs(struct pci_dev *dev) > > > > /* Upstream Forwarding */ > > > > ctrl |= (cap & PCI_ACS_UF); > > > > > > > > + /* Enable Translation Blocking for external devices */ > > > > + if (dev->external_facing || dev->untrusted) { > > > > + if (cap & PCI_ACS_TB) > > > > + ctrl |= PCI_ACS_TB; > > > > + else if (dev->external_facing) > > > > + pci_warn(dev, "ACS: No Translation Blocking on external-facing dev\n"); > > > > + } > > > > > > IIUC, this means that external devices can *never* use ATS and > > > can never cache translations. > > Yes, but it already exists today (and this patch doesn't change that): > 521376741b2c2 "PCI/ATS: Only enable ATS for trusted devices" > > IMHO any external device trying to send ATS traffic despite having ATS > disabled should count as a bad intent. And this patch is trying to > plug that loophole, by blocking the AT traffic from devices that we do > not expect to see AT from anyway. Thinking about this some more, I wonder if Linux should: - Explicitly disable ATS for every device at enumeration-time, e.g., in pci_init_capabilities(), - Enable PCI_ACS_TB for every device (not just external-facing or untrusted ones), - Disable PCI_ACS_TB for the relevant devices along the path only when enabling ATS. One nice thing about doing that is that the "untrusted" test would be only in pci_enable_ats(), and we wouldn't need one in pci_std_enable_acs(). It's possible BIOS gives us devices with ATS enabled, and this might break them, but that seems like something we'd want to find out about. Bjorn