From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bjorn Helgaas Subject: Re: [PATCH v3 3/7] PCI: OF: Allow endpoints to bypass the iommu Date: Fri, 12 Oct 2018 14:41:59 -0500 Message-ID: <20181012194158.GX5906@bhelgaas-glaptop.roam.corp.google.com> References: <20181012145917.6840-1-jean-philippe.brucker@arm.com> <20181012145917.6840-4-jean-philippe.brucker@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20181012145917.6840-4-jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Jean-Philippe Brucker Cc: mark.rutland-5wv7dgnIgG8@public.gmane.org, peter.maydell-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, tnowicki-M3mlKVOIwJVv6pq1l3V1OdBPR1lH4CV8@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, will.deacon-5wv7dgnIgG8@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, marc.zyngier-5wv7dgnIgG8@public.gmane.org, robin.murphy-5wv7dgnIgG8@public.gmane.org, kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org List-Id: devicetree@vger.kernel.org s/iommu/IOMMU/ in subject On Fri, Oct 12, 2018 at 03:59:13PM +0100, Jean-Philippe Brucker wrote: > Using the iommu-map binding, endpoints in a given PCI domain can be > managed by different IOMMUs. Some virtual machines may allow a subset of > endpoints to bypass the IOMMU. In some case the IOMMU itself is presented s/case/cases/ > as a PCI endpoint (e.g. AMD IOMMU and virtio-iommu). Currently, when a > PCI root complex has an iommu-map property, the driver requires all > endpoints to be described by the property. Allow the iommu-map property to > have gaps. I'm not an IOMMU or virtio expert, so it's not obvious to me why it is safe to allow devices to bypass the IOMMU. Does this mean a typo in iommu-map could inadvertently allow devices to bypass it? Should we indicate something in dmesg (and/or sysfs) about devices that bypass it? > Relaxing of_pci_map_rid also allows the msi-map property to have gaps, s/of_pci_map_rid/of_pci_map_rid()/ > which is invalid since MSIs always reach an MSI controller. Thankfully > Linux will error out later, when attempting to find an MSI domain for the > device. Not clear to me what "error out" means here. In a userspace program, I would infer that the program exits with an error message, but I doubt you mean that Linux exits. > Signed-off-by: Jean-Philippe Brucker > --- > drivers/pci/of.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > index 1836b8ddf292..2f5015bdb256 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -451,9 +451,10 @@ int of_pci_map_rid(struct device_node *np, u32 rid, > return 0; > } > > - pr_err("%pOF: Invalid %s translation - no match for rid 0x%x on %pOF\n", > - np, map_name, rid, target && *target ? *target : NULL); > - return -EFAULT; > + /* Bypasses translation */ > + if (id_out) > + *id_out = rid; > + return 0; > } > > #if IS_ENABLED(CONFIG_OF_IRQ) > -- > 2.19.1 > 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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 E57D8C6787C for ; Fri, 12 Oct 2018 19:42:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A1B16214C4 for ; Fri, 12 Oct 2018 19:42:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="dZFWTuoc" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1B16214C4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-pci-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726232AbeJMDQE (ORCPT ); Fri, 12 Oct 2018 23:16:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:58574 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726227AbeJMDQE (ORCPT ); Fri, 12 Oct 2018 23:16:04 -0400 Received: from localhost (unknown [69.71.4.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D07A420865; Fri, 12 Oct 2018 19:42:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1539373321; bh=HshiW5WzSWIcBsOfg5j9VjAfkwfF3ZhuopNc+3rGYz4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dZFWTuocqAiJL1bK5vg26/8ViKfQh1+jbbyStLb1BL73pwTadxQb7Ng6XqC43Q5w2 2/NJGIOA/3pJOmsNWB8tCA9lYaqcw9zW/qB5QJAkpyK8qOKTuzW9WtYGkO60uXZtoy SFEoO8v+0Nkv2BmxT9mMoWEgOkg1N33268KkDStQ= Date: Fri, 12 Oct 2018 14:41:59 -0500 From: Bjorn Helgaas To: Jean-Philippe Brucker Cc: iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, kvmarm@lists.cs.columbia.edu, peter.maydell@linaro.org, joro@8bytes.org, mst@redhat.com, jasowang@redhat.com, robh+dt@kernel.org, mark.rutland@arm.com, eric.auger@redhat.com, tnowicki@caviumnetworks.com, kevin.tian@intel.com, marc.zyngier@arm.com, robin.murphy@arm.com, will.deacon@arm.com, lorenzo.pieralisi@arm.com Subject: Re: [PATCH v3 3/7] PCI: OF: Allow endpoints to bypass the iommu Message-ID: <20181012194158.GX5906@bhelgaas-glaptop.roam.corp.google.com> References: <20181012145917.6840-1-jean-philippe.brucker@arm.com> <20181012145917.6840-4-jean-philippe.brucker@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181012145917.6840-4-jean-philippe.brucker@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org s/iommu/IOMMU/ in subject On Fri, Oct 12, 2018 at 03:59:13PM +0100, Jean-Philippe Brucker wrote: > Using the iommu-map binding, endpoints in a given PCI domain can be > managed by different IOMMUs. Some virtual machines may allow a subset of > endpoints to bypass the IOMMU. In some case the IOMMU itself is presented s/case/cases/ > as a PCI endpoint (e.g. AMD IOMMU and virtio-iommu). Currently, when a > PCI root complex has an iommu-map property, the driver requires all > endpoints to be described by the property. Allow the iommu-map property to > have gaps. I'm not an IOMMU or virtio expert, so it's not obvious to me why it is safe to allow devices to bypass the IOMMU. Does this mean a typo in iommu-map could inadvertently allow devices to bypass it? Should we indicate something in dmesg (and/or sysfs) about devices that bypass it? > Relaxing of_pci_map_rid also allows the msi-map property to have gaps, s/of_pci_map_rid/of_pci_map_rid()/ > which is invalid since MSIs always reach an MSI controller. Thankfully > Linux will error out later, when attempting to find an MSI domain for the > device. Not clear to me what "error out" means here. In a userspace program, I would infer that the program exits with an error message, but I doubt you mean that Linux exits. > Signed-off-by: Jean-Philippe Brucker > --- > drivers/pci/of.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/of.c b/drivers/pci/of.c > index 1836b8ddf292..2f5015bdb256 100644 > --- a/drivers/pci/of.c > +++ b/drivers/pci/of.c > @@ -451,9 +451,10 @@ int of_pci_map_rid(struct device_node *np, u32 rid, > return 0; > } > > - pr_err("%pOF: Invalid %s translation - no match for rid 0x%x on %pOF\n", > - np, map_name, rid, target && *target ? *target : NULL); > - return -EFAULT; > + /* Bypasses translation */ > + if (id_out) > + *id_out = rid; > + return 0; > } > > #if IS_ENABLED(CONFIG_OF_IRQ) > -- > 2.19.1 >