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=-2.2 required=3.0 tests=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 908EDCA9EBC for ; Fri, 25 Oct 2019 14:42:02 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (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 6497D2064A for ; Fri, 25 Oct 2019 14:42:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6497D2064A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 3071BD38; Fri, 25 Oct 2019 14:42:02 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id BB3AAD2E for ; Fri, 25 Oct 2019 14:42:00 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 6873114D for ; Fri, 25 Oct 2019 14:42:00 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Oct 2019 07:41:59 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,229,1569308400"; d="scan'208";a="223939301" Received: from allen-box.sh.intel.com (HELO [10.239.159.136]) ([10.239.159.136]) by fmsmga004.fm.intel.com with ESMTP; 25 Oct 2019 07:41:57 -0700 Subject: Re: [PATCH v7 03/11] iommu/vt-d: Add custom allocator for IOASID To: "Tian, Kevin" , Jacob Pan References: <1571946904-86776-1-git-send-email-jacob.jun.pan@linux.intel.com> <1571946904-86776-4-git-send-email-jacob.jun.pan@linux.intel.com> <20191024214311.43d76a5c@jacob-builder> From: Lu Baolu Message-ID: Date: Fri, 25 Oct 2019 22:39:23 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Cc: "Raj, Ashok" , Jean-Philippe Brucker , "iommu@lists.linux-foundation.org" , LKML , Alex Williamson , David Woodhouse , Jonathan Cameron X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Hi, On 10/25/19 2:40 PM, Tian, Kevin wrote: >>>> ioasid_register_allocator(&iommu->pasid_allocator); >>>> + if (ret) { >>>> + pr_warn("Custom PASID allocator >>>> registeration failed\n"); >>>> + /* >>>> + * Disable scalable mode on this >>>> IOMMU if there >>>> + * is no custom allocator. Mixing >>>> SM capable vIOMMU >>>> + * and non-SM vIOMMU are not >>>> supported. >>>> + */ >>>> + intel_iommu_sm = 0; >>> It's insufficient to disable scalable mode by only clearing >>> intel_iommu_sm. The DMA_RTADDR_SMT bit in root entry has already >> been >>> set. Probably, you need to >>> >>> for each iommu >>> clear DMA_RTADDR_SMT in root entry >>> >>> Alternatively, since vSVA is the only customer of this custom PASID >>> allocator, is it possible to only disable SVA here? >>> >> Yeah, I think disable SVA is better. We can still do gIOVA in SM. I >> guess we need to introduce a flag for sva_enabled. > I'm not sure whether tying above logic to SVA is the right approach. > If vcmd interface doesn't work, the whole SM mode doesn't make > sense which is based on PASID-granular protection (SVA is only one > usage atop). If the only remaining usage of SM is to map gIOVA using > reserved PASID#0, then why not disabling SM and just fallback to > legacy mode? > > Based on that I prefer to disabling the SM mode completely (better > through an interface), and move the logic out of CONFIG_INTEL_ > IOMMU_SVM > Unfortunately, it is dangerous to disable SM after boot. SM uses different root/device contexts and pasid table formats. Disabling SM after boot requires changing above from SM format into legacy format. Since ioasid registration failure is a rare case. How about moving this part of code up to the early stage of intel_iommu_init() and returning error if hardware present vcmd capability but software fails to register a custom ioasid allocator? Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu