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,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 6250DC433DF for ; Fri, 31 Jul 2020 18:14:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FEF02177B for ; Fri, 31 Jul 2020 18:14:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="T75L1Vmu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387513AbgGaSO0 (ORCPT ); Fri, 31 Jul 2020 14:14:26 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:51843 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730040AbgGaSO0 (ORCPT ); Fri, 31 Jul 2020 14:14:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1596219264; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=h5RCnyOaFSBCI3Qz6zkjCZ63e5lETgkYf1JyHMYznJQ=; b=T75L1VmuKn87aEA1Ac94iyH6oSjK3TP2MBmqr+En+JSWWG6gfAl3LybtuKvoVZ/q+ME/dp 0jMufEOvwkvNKx0k7Tvql4HLDpDUyVufgt9s1NgYyqWwJ35Qhn1sCA+8/KkHEUGEf0UxWZ LjreQFuKIz4Qc+EkY9dSoKc1LI0XJi0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-491-wSMzoo6iOy6LHz813pxjOA-1; Fri, 31 Jul 2020 14:14:22 -0400 X-MC-Unique: wSMzoo6iOy6LHz813pxjOA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5CA0318839CD; Fri, 31 Jul 2020 18:14:20 +0000 (UTC) Received: from x1.home (ovpn-112-71.phx2.redhat.com [10.3.112.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 732831002388; Fri, 31 Jul 2020 18:14:19 +0000 (UTC) Date: Fri, 31 Jul 2020 12:14:18 -0600 From: Alex Williamson To: Lu Baolu Cc: Joerg Roedel , Robin Murphy , Jean-Philippe Brucker , Cornelia Huck , Kevin Tian , Ashok Raj , Dave Jiang , Liu Yi L , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v3 3/4] iommu: Add iommu_aux_get_domain_for_dev() Message-ID: <20200731121418.0274afb8@x1.home> In-Reply-To: <06fd91c1-a978-d526-7e2b-fec619a458e4@linux.intel.com> References: <20200714055703.5510-1-baolu.lu@linux.intel.com> <20200714055703.5510-4-baolu.lu@linux.intel.com> <20200729142507.182cd18a@x1.home> <06fd91c1-a978-d526-7e2b-fec619a458e4@linux.intel.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 31 Jul 2020 14:30:03 +0800 Lu Baolu wrote: > Hi Alex, > > On 2020/7/30 4:25, Alex Williamson wrote: > > On Tue, 14 Jul 2020 13:57:02 +0800 > > Lu Baolu wrote: > > > >> The device driver needs an API to get its aux-domain. A typical usage > >> scenario is: > >> > >> unsigned long pasid; > >> struct iommu_domain *domain; > >> struct device *dev = mdev_dev(mdev); > >> struct device *iommu_device = vfio_mdev_get_iommu_device(dev); > >> > >> domain = iommu_aux_get_domain_for_dev(dev); > >> if (!domain) > >> return -ENODEV; > >> > >> pasid = iommu_aux_get_pasid(domain, iommu_device); > >> if (pasid <= 0) > >> return -EINVAL; > >> > >> /* Program the device context */ > >> .... > >> > >> This adds an API for such use case. > >> > >> Suggested-by: Alex Williamson > >> Signed-off-by: Lu Baolu > >> --- > >> drivers/iommu/iommu.c | 18 ++++++++++++++++++ > >> include/linux/iommu.h | 7 +++++++ > >> 2 files changed, 25 insertions(+) > >> > >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > >> index cad5a19ebf22..434bf42b6b9b 100644 > >> --- a/drivers/iommu/iommu.c > >> +++ b/drivers/iommu/iommu.c > >> @@ -2817,6 +2817,24 @@ void iommu_aux_detach_group(struct iommu_domain *domain, > >> } > >> EXPORT_SYMBOL_GPL(iommu_aux_detach_group); > >> > >> +struct iommu_domain *iommu_aux_get_domain_for_dev(struct device *dev) > >> +{ > >> + struct iommu_domain *domain = NULL; > >> + struct iommu_group *group; > >> + > >> + group = iommu_group_get(dev); > >> + if (!group) > >> + return NULL; > >> + > >> + if (group->aux_domain_attached) > >> + domain = group->domain; > > Why wouldn't the aux domain flag be on the domain itself rather than > > the group? Then if we wanted sanity checking in patch 1/ we'd only > > need to test the flag on the object we're provided. > > Agreed. Given that a group may contain both non-aux and aux devices, > adding such flag in iommu_group doesn't make sense. > > > > > If we had such a flag, we could create an iommu_domain_is_aux() > > function and then simply use iommu_get_domain_for_dev() and test that > > it's an aux domain in the example use case. It seems like that would > > resolve the jump from a domain to an aux-domain just as well as adding > > this separate iommu_aux_get_domain_for_dev() interface. The is_aux > > test might also be useful in other cases too. > > Let's rehearsal our use case. > > unsigned long pasid; > struct iommu_domain *domain; > struct device *dev = mdev_dev(mdev); > struct device *iommu_device = vfio_mdev_get_iommu_device(dev); > > [1] domain = iommu_get_domain_for_dev(dev); > if (!domain) > return -ENODEV; > > [2] pasid = iommu_aux_get_pasid(domain, iommu_device); > if (pasid <= 0) > return -EINVAL; > > /* Program the device context */ > .... > > The reason why I add this iommu_aux_get_domain_for_dev() is that we need > to make sure the domain got at [1] is valid to be used at [2]. > > https://lore.kernel.org/linux-iommu/20200707150408.474d81f1@x1.home/ Yep, I thought that was a bit of a leap in logic. > When calling into iommu_aux_get_pasid(), the iommu driver should make > sure that @domain is a valid aux-domain for @iommu_device. Hence, for > our use case, it seems that there's no need for a is_aux_domain() api. > > Anyway, I'm not against adding a new is_aux_domain() api if there's a > need elsewhere. I think it could work either way, we could have an iommu_get_aux_domain_for_dev() which returns NULL if the domain is not an aux domain, or we could use iommu_get_domain_for_dev() and the caller could test the domain with iommu_is_aux_domain() if they need to confirm if it's an aux domain. The former could even be written using the latter, a wrapper of iommu_get_domain_for_dev() that checks aux property before returning. Thanks, Alex