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,USER_AGENT_SANE_2 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 AFC8CCA9EC0 for ; Mon, 28 Oct 2019 22:44:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 83217208C0 for ; Mon, 28 Oct 2019 22:44:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729764AbfJ1Woi (ORCPT ); Mon, 28 Oct 2019 18:44:38 -0400 Received: from mga11.intel.com ([192.55.52.93]:12461 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfJ1Woi (ORCPT ); Mon, 28 Oct 2019 18:44:38 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Oct 2019 15:44:37 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,241,1569308400"; d="scan'208";a="210976010" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by fmsmga001.fm.intel.com with ESMTP; 28 Oct 2019 15:44:36 -0700 Date: Mon, 28 Oct 2019 15:49:00 -0700 From: Jacob Pan To: "Tian, Kevin" Cc: Lu Baolu , "iommu@lists.linux-foundation.org" , LKML , Joerg Roedel , "David Woodhouse" , Alex Williamson , Jean-Philippe Brucker , "Liu, Yi L" , "Raj, Ashok" , Christoph Hellwig , "Jonathan Cameron" , Eric Auger , jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v7 03/11] iommu/vt-d: Add custom allocator for IOASID Message-ID: <20191028154900.0be0a48f@jacob-builder> In-Reply-To: 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> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Oct 2019 15:52:39 +0000 "Tian, Kevin" wrote: > > From: Lu Baolu [mailto:baolu.lu@linux.intel.com] > > Sent: Friday, October 25, 2019 10:39 PM > > > > 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. > > You are correct. > > > > > 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? > > > > It makes sense to me. > sounds good to me too, the earlier the less to clean up. > Thanks > Kevin [Jacob Pan]