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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 76C6FC433DF for ; Wed, 27 May 2020 02:51:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 59C0A2075F for ; Wed, 27 May 2020 02:51:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727117AbgE0Cvw (ORCPT ); Tue, 26 May 2020 22:51:52 -0400 Received: from mga05.intel.com ([192.55.52.43]:63469 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725893AbgE0Cvw (ORCPT ); Tue, 26 May 2020 22:51:52 -0400 IronPort-SDR: l4xK0HEBXkK09YnzS8cRwkjSJeePE0qnzVd0Exn5Qy4xZhvBGIuinbE1IMRXMUVLQVnvI5ki7I MQ92LCEUOR/Q== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 May 2020 19:51:52 -0700 IronPort-SDR: IZHzwPU39n6YAGz34ybNx/oUi7IFJXZJV3yMToik2/+nyg9lDC5WwFobtEfKzEIgqFOe58oAvs rXns1gJJcfAQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,439,1583222400"; d="scan'208";a="270302681" Received: from zalvear-mobl.amr.corp.intel.com (HELO [10.254.67.58]) ([10.254.67.58]) by orsmga006.jf.intel.com with ESMTP; 26 May 2020 19:51:51 -0700 Subject: Re: [PATCH] iommu: Relax ACS requirement for Intel RCiEP devices. To: Ashok Raj , linux-pci@vger.kernel.org, Bjorn Helgaas , Joerg Roedel Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Lu Baolu , Alex Williamson , Darrel Goeddel , Mark Scott , Romil Sharma References: <1590531455-19757-1-git-send-email-ashok.raj@intel.com> From: "Kuppuswamy, Sathyanarayanan" Message-ID: <6735b6d5-a04f-57ae-8e3f-f818f07a57a4@linux.intel.com> Date: Tue, 26 May 2020 19:51:51 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <1590531455-19757-1-git-send-email-ashok.raj@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 5/26/20 3:17 PM, Ashok Raj wrote: > All Intel platforms guarantee that all root complex implementations > must send transactions up to IOMMU for address translations. Hence for > RCiEP devices that are Vendor ID Intel, can claim exception for lack of > ACS support. > > > 3.16 Root-Complex Peer to Peer Considerations > When DMA remapping is enabled, peer-to-peer requests through the > Root-Complex must be handled > as follows: > • The input address in the request is translated (through first-level, > second-level or nested translation) to a host physical address (HPA). > The address decoding for peer addresses must be done only on the > translated HPA. Hardware implementations are free to further limit > peer-to-peer accesses to specific host physical address regions > (or to completely disallow peer-forwarding of translated requests). > • Since address translation changes the contents (address field) of > the PCI Express Transaction Layer Packet (TLP), for PCI Express > peer-to-peer requests with ECRC, the Root-Complex hardware must use > the new ECRC (re-computed with the translated address) if it > decides to forward the TLP as a peer request. > • Root-ports, and multi-function root-complex integrated endpoints, may > support additional peerto-peer control features by supporting PCI Express > Access Control Services (ACS) capability. Refer to ACS capability in > PCI Express specifications for details. > > Since Linux didn't give special treatment to allow this exception, certain > RCiEP MFD devices are getting grouped in a single iommu group. This > doesn't permit a single device to be assigned to a guest for instance. > > In one vendor system: Device 14.x were grouped in a single IOMMU group. > > /sys/kernel/iommu_groups/5/devices/0000:00:14.0 > /sys/kernel/iommu_groups/5/devices/0000:00:14.2 > /sys/kernel/iommu_groups/5/devices/0000:00:14.3 > > After the patch: > /sys/kernel/iommu_groups/5/devices/0000:00:14.0 > /sys/kernel/iommu_groups/5/devices/0000:00:14.2 > /sys/kernel/iommu_groups/6/devices/0000:00:14.3 <<< new group > > 14.0 and 14.2 are integrated devices, but legacy end points. > Whereas 14.3 was a PCIe compliant RCiEP. > > 00:14.3 Network controller: Intel Corporation Device 9df0 (rev 30) > Capabilities: [40] Express (v2) Root Complex Integrated Endpoint, MSI 00 > > This permits assigning this device to a guest VM. > > Fixes: f096c061f552 ("iommu: Rework iommu_group_get_for_pci_dev()") > Signed-off-by: Ashok Raj > To: Joerg Roedel > To: Bjorn Helgaas > Cc: linux-kernel@vger.kernel.org > Cc: iommu@lists.linux-foundation.org > Cc: Lu Baolu > Cc: Alex Williamson > Cc: Darrel Goeddel > Cc: Mark Scott , > Cc: Romil Sharma > Cc: Ashok Raj > --- > drivers/iommu/iommu.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index 2b471419e26c..31b595dfedde 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -1187,7 +1187,18 @@ static struct iommu_group *get_pci_function_alias_group(struct pci_dev *pdev, > struct pci_dev *tmp = NULL; > struct iommu_group *group; > > - if (!pdev->multifunction || pci_acs_enabled(pdev, REQ_ACS_FLAGS)) > + /* > + * Intel VT-d Specification Section 3.16, Root-Complex Peer to Peer > + * Considerations manadate that all transactions in RCiEP's and > + * even Integrated MFD's *must* be sent up to the IOMMU. P2P is > + * only possible on translated addresses. This gives enough > + * guarantee that such devices can be forgiven for lack of ACS > + * support. > + */ > + if (!pdev->multifunction || > + (pdev->vendor == PCI_VENDOR_ID_INTEL && > + pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END) || > + pci_acs_enabled(pdev, REQ_ACS_FLAGS)) Looks good to me. Reviewed-by: Kuppuswamy Sathyanarayanan > return NULL; > > for_each_pci_dev(tmp) { >