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 5ADB9C4725A for ; Tue, 5 May 2020 06:11:14 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 03B64206A5 for ; Tue, 5 May 2020 06:11:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 03B64206A5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id C239A22829; Tue, 5 May 2020 06:11:13 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id UrzAjvCWlZS6; Tue, 5 May 2020 06:11:12 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 7BC0922803; Tue, 5 May 2020 06:11:12 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6DB9EC088C; Tue, 5 May 2020 06:11:12 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id C9D63C0175 for ; Tue, 5 May 2020 06:11:10 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id B0A76863A1 for ; Tue, 5 May 2020 06:11:10 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id h4kOrMnlGzCA for ; Tue, 5 May 2020 06:11:09 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by fraxinus.osuosl.org (Postfix) with ESMTPS id 7BB67863A4 for ; Tue, 5 May 2020 06:11:09 +0000 (UTC) IronPort-SDR: Kkp8t1z5Ym1YLOzvdFYyKm0GfrCV96OK2mSS85eq9VZMSb/n2SXmmf2gRIS5jwS4w2EaVUOn/b knHJGSyrGv+Q== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 May 2020 23:11:08 -0700 IronPort-SDR: V7xGuKgTmHsrqJ1LWIleEXUUPdshBrPcR0pCTD8WwfbnMI/fV4SMleOaml1JQGO/MXh5MfGbj9 ZEjnYNeGfOTw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,354,1583222400"; d="scan'208";a="304386453" Received: from araj-mobl1.jf.intel.com ([10.254.74.162]) by FMSMGA003.fm.intel.com with ESMTP; 04 May 2020 23:11:07 -0700 Date: Mon, 4 May 2020 23:11:07 -0700 From: "Raj, Ashok" To: Alex Williamson Subject: Re: [PATCH] iommu: Relax ACS requirement for RCiEP devices. Message-ID: <20200505061107.GA22974@araj-mobl1.jf.intel.com> References: <1588653736-10835-1-git-send-email-ashok.raj@intel.com> <20200504231936.2bc07fe3@x1.home> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200504231936.2bc07fe3@x1.home> User-Agent: Mutt/1.9.1 (2017-09-22) Cc: Ashok Raj , Darrel Goeddel , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Mark Scott , Romil Sharma , Bjorn Helgaas X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" Hi Alex + Joerg, accidently missed in the Cc. On Mon, May 04, 2020 at 11:19:36PM -0600, Alex Williamson wrote: > On Mon, 4 May 2020 21:42:16 -0700 > Ashok Raj wrote: > > > PCIe Spec recommends we can relax ACS requirement for RCIEP devices. > > > > PCIe 5.0 Specification. > > 6.12 Access Control Services (ACS) > > Implementation of ACS in RCiEPs is permitted but not required. It is > > explicitly permitted that, within a single Root Complex, some RCiEPs > > implement ACS and some do not. It is strongly recommended that Root Complex > > implementations ensure that all accesses originating from RCiEPs > > (PFs and VFs) without ACS capability are first subjected to processing by > > the Translation Agent (TA) in the Root Complex before further decoding and > > processing. The details of such Root Complex handling are outside the scope > > of this specification. > > > > 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 | 15 ++++++++++++++- > > 1 file changed, 14 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > > index 2b471419e26c..5744bd65f3e2 100644 > > --- a/drivers/iommu/iommu.c > > +++ b/drivers/iommu/iommu.c > > @@ -1187,7 +1187,20 @@ 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)) > > + /* > > + * PCI Spec 5.0, Section 6.12 Access Control Service > > + * Implementation of ACS in RCiEPs is permitted but not required. > > + * It is explicitly permitted that, within a single Root > > + * Complex, some RCiEPs implement ACS and some do not. It is > > + * strongly recommended that Root Complex implementations ensure > > + * that all accesses originating from RCiEPs (PFs and VFs) without > > + * ACS capability are first subjected to processing by the Translation > > + * Agent (TA) in the Root Complex before further decoding and > > + * processing. > > + */ > > Is the language here really strong enough to make this change? ACS is > an optional feature, so being permitted but not required is rather > meaningless. The spec is also specifically avoiding the words "must" > or "shall" and even when emphasized with "strongly", we still only have > a recommendation that may or may not be honored. This seems like a > weak basis for assuming that RCiEPs universally honor this > recommendation. Thanks, > We are speaking about PCIe spec, where people write it about 5 years ahead and every vendor tries to massage their product behavior with vague words like this.. :) But honestly for any any RCiEP, or even integrated endpoints, there is no way to send them except up north. These aren't behind a RP. I did check with couple folks who are part of the SIG, and seem to agree that ACS treatment for RCiEP's doesn't mean much. I understand the language isn't strong, but it doesn't seem like ACS should be a strong requirement for RCiEP's and reasonable to relax. What are your thoughts? Cheers, Ashok > > > + if (!pdev->multifunction || > > + (pci_pcie_type(pdev) == PCI_EXP_TYPE_RC_END) || > > + pci_acs_enabled(pdev, REQ_ACS_FLAGS)) > > return NULL; > > > > for_each_pci_dev(tmp) { > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu